TSI Incorporated 3480 User Manual

Aerosol Generators

Model 3480

Electrospray Aerosol Generator

User’s Manual

P/N 1933793, Revision E

March 2008

Model 3480

Electrospray
Aerosol Generator

User’s Manual

Product Overview 1

Unpacking and Setting

2

Up the System

Controls, Indicators, and

3

Connectors

Operating the

4

Electrospray

Maintenance 5

Troubleshooting 6

Contacting Customer

7

Service

Appendixes

Manual History

The following is a manual history of the Model 3480 Electrospray
Aerosol Generator (Part Number 1933793).

Revision Date

Preliminary Version March 1999
Final May 1999
A July 2000
B February 2002
C October 2002
D October 2003
E March 2008

In Revision A, TSI’s Limitation of Warranty and Liability was
updated.

In Revision B, Table 2-1 was updated, Appendix C was removed,
and a few minor corrections were made throughout manual.

In Revision C, TSI’s phone numbers and address were updated.
Front and back manual covers were updated.

In Revision D, directions for replacing the capillaries were updated
due to a change to the capillary design. Miscellaneous changes
were made throughout manual and pictures were updated.

In Revision E, manual was updated with new logo and look. The
equation used for calculating final particle diameter D
a sucrose solution with the Electrospray was corrected and
simplified. Relationship between viscosity of solution and
concentration was removed from the discussion and reader was
referred to a related publication for more information.

when using

p

iv

Warranty

Part Number 1933793 / Revision E / March 2007
Copyright ©TSI Incorporated / 2008 / All rights reserved.
Address TSI Incorporated / 500 Cardigan Road / Shoreview, MN 55126 / USA
Fax No. 651-490-3824
E-mail Address [e-mail]

Limitation of Warranty
and Liability
(effective July 2000)

Service Policy Knowing that inoperative or defective instruments are as detrimental to TSI as they

Seller warrants the goods sold hereunder, under normal use and service as
described in the operator's manual, shall be free from defects in workmanship and
material for (12) months, or the length of time specified in the operator's manual,
from the date of shipment to the customer. This warranty period is inclusive of any
statutory warranty. This limited warranty is subject to the following exclusions:

a. Hot-wire or hot-film sensors used with research anemometers, and certain other

components when indicated in specifications, are warranted for 90 days from
the date of shipment.

b. Parts repaired or replaced as a result of repair services are warranted to be free

from defects in workmanship and material, under normal use, for 90 days from
the date of shipment.

c. Seller does not provide any warranty on finished goods manufactured by others

or on any fuses, batteries or other consumable materials. Only the original
manufacturer's warranty applies.

d. Unless specifically authorized in a separate writing by Seller, Seller makes no

warranty with respect to, and shall have no liability in connection with, goods
which are incorporated into other products or equipment, or which are modified
by any person other than Seller.

The foregoing is IN LIEU OF all other warranties and is subject to the LIMITATIONS
stated herein. NO OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR
PARTICULAR PURPOSE OR MERCHANTABILITY IS MADE.

TO THE EXTENT PERMITTED BY LAW, THE EXCLUSIVE REMEDY OF THE USER
OR BUYER, AND THE LIMIT OF SELLER'S LIABILITY FOR ANY AND ALL LOSSES,
INJURIES, OR DAMAGES CONCERNING THE GOODS (INCLUDING CLAIMS BASED
ON CONTRACT, NEGLIGENCE, TORT, STRICT LIABILITY OR OTHERWISE) SHALL
BE THE RETURN OF GOODS TO SELLER AND THE REFUND OF THE PURCHASE
PRICE, OR, AT THE OPTION OF SELLER, THE REPAIR OR REPLACEMENT OF THE
GOODS. IN NO EVENT SHALL SELLER BE LIABLE FOR ANY SPECIAL,
CONSEQUENTIAL OR INCIDENTAL DAMAGES. SELLER SHALL NOT BE
RESPONSIBLE FOR INSTALLATION, DISMANTLING OR REINSTALLATION COSTS
OR CHARGES. No Action, regardless of form, may be brought against Seller more
than 12 months after a cause of action has accrued. The goods returned under
warranty to Seller's factory shall be at Buyer's risk of loss, and will be returned, if at
all, at Seller's risk of loss.

Buyer and all users are deemed to have accepted this LIMITATION OF WARRANTY
AND LIABILITY, which contains the complete and exclusive limited warranty of
Seller. This LIMITATION OF WARRANTY AND LIABILITY may not be amended,
modified or its terms waived, except by writing signed by an Officer of Seller.

are to our customers, our service policy is designed to give prompt attention to any
problems. If any malfunction is discovered, please contact your nearest sales office
or representative, or call TSI’s Customer Service department at 1-800-874-2811
(USA) or [phone].

v

Contents

Manual History ......................................................................iv

Warranty.................................................................................

Safety ....................................................................................

Labels .....................................................................................

Description of Caution/Warning Symbols ..............................

Caution ...............................................................................

Warning .............................................................................

Caution or Warning Symbols..............................................

Radiation Safety ....................................................................

Chemical Safety .....................................................................

Electrical Safety ......................................................................

About This Manual ..............................................................

Purpose.................................................................................

Related Product Literature ....................................................

Getting Help..........................................................................

Submitting Comments .........................................................

CHAPTER 1 Product Overview..............................................1-

Product Description ..............................................................1-

Applications ..........................................................................1-

How the Electrospray Operates .............................................1-

CHAPTER 2 Unpacking and Setting Up the System...............2-

Packing List ..........................................................................2-

Mounting the Instrument ......................................................2-

Ventilation Requirements ................................................... 2-

Checking the Zero of the Pressure Gauge ........................... 2-

Power Connection .................................................................2-

Analog Output ......................................................................2-

Filtered Air Input ..................................................................2-

Input.............................................................................. 2-4

CO

2

Installing the Ionizer .............................................................2-

xiii
xiii
xiii

xvii

xvii
xvii
xvii

xviii

v

xi

xi
xii
xii

xiv

xv

1

1
2
2

1

1
2
2
3
3
4
4

5

CHAPTER 3 Controls, Indicators, and Connectors ................ 3-

Front Panel ...........................................................................3-

LED Displays .....................................................................3-

Voltage Adjustment Knob ...................................................3-

Indicators...........................................................................3-

Rotameters.........................................................................3-

Pressure Regulator and Gauge ...........................................3-

Pressure Chamber.............................................................. 3-

Viewing Window ................................................................. 3-

Ionizer Retainer .................................................................. 3-

Back Panel ............................................................................ 3-

Aerosol Exit........................................................................ 3-

Analog Output.................................................................... 3-

1

1
1
2
2
3
3
3
3
3
4
4
5

vii

AC Power Connector...........................................................3-5

Filtered Air Inlet ................................................................. 3-

Inlet ............................................................................3-5

CO

2

Internal Components ............................................................3-

Capillary ............................................................................3-

Electrospray Chamber........................................................ 3-

High-Voltage Fitting and Shield .......................................... 3-

Power Supply .....................................................................3-

Main PCB........................................................................... 3-

High-Voltage Supply Module ..............................................3-

Interlock Switch .................................................................3-

Filters ................................................................................3-

5

6
6
6
6
7
7
7
8
8

CHAPTER 4 Operating the Electrospray ............................... 4-

Preparing Samples ................................................................ 4-

Preparing a Buffer Solution ................................................ 4-

Measuring and Adjusting Conductivity............................... 4-

Measuring and Adjusting pH .............................................. 4-

Typical Solutes................................................................... 4-

Starting Up the Electrospray .................................................4-

Generating Aerosols ..............................................................4-

Changing Samples ................................................................4-

Shutting Down the Electrospray............................................ 4-

CHAPTER 5 Maintenance..................................................... 5-

Periodic Maintenance ............................................................5-

Purging the Capillary..........................................................5-

Cleaning the Orifice Plate ................................................... 5-

Cleaning the Aerosol Exit Port ............................................ 5-

Cleaning the Viewing Window Lens ....................................5-

Replacing the Ionizer ..........................................................5-

Cleaning the Electrospray Chamber ...................................5-

Performing an Air Leak Test ...............................................5-

Cleaning the Pressure Chamber ....................................... 5-

Special Maintenance ........................................................... 5-

Removing the Capillary ....................................................5-

Cleaning the Capillary Tip ................................................ 5-

Installing the Capillary ..................................................... 5-

Adjusting the Position of the Capillary Tip........................ 5-

Adjusting the Position of the Capillary and the

Platinum Wire in the Pressure Chamber........................ 5-

Reversing the High-Voltage Polarity.................................. 5-

Cleaning the Pressure Regulator ......................................5-

Cleaning the Rotameters ..................................................5-

Replacing the Filters......................................................... 5-

Replacement Parts ..............................................................5-

1

1
2
2
3
3
5
6
8
8

1

1
1
3
4
4
5
6

8
10
12
12
14
14
15

15
16
19
19
19
19

CHAPTER 6 Troubleshooting................................................ 6-

Electrospray Operation is Unstable ....................................... 6-

Unplugging the Capillary....................................................... 6-

Applying Back Pressure to the Capillary............................. 6-

CHAPTER 7 Contacting Customer Service............................ 7-

Technical Contacts................................................................ 7-

Returning the Electrospray for Service ..................................7-

viii Model 3480 Electrospray Aerosol Generator

1

1

3

3

1

1

1

APPENDIX A Model 3480 Specifications ...............................A-1

Pressure Regulator Maintenance ........................................A-

Rotameter Maintenance......................................................A-

2
3

Figures

APPENDIX B Theory of Operation.........................................B-

System Description .............................................................. B-

Capillary Flow Characteristics.............................................. B-

Calculating Primary Droplet Diameter.................................. B-

Electrospray Chamber.......................................................... B-

Equilibrium Charging Theory ............................................... B-

Air and CO

Voltage and Current Measurement....................................... B-

Voltage Measurement ........................................................ B-

Current Measurement ....................................................... B-

Selected References.............................................................. B-

Index

Reader’s Comments

S-1 Location of Warning and Information Labels....................... xii

1-1 Model 3480 Electrospray Aerosol Generator ..................... 1-

2-1 Bottom View of Electrospray Aerosol Generator Showing

Location of Rubber Feet................................................. 2-

2-2 Installing the Ionizer......................................................... 2-

Flow Control ..................................................... B-7

2

1

2
6

1

1
2
4
4
5

9
9
9
9

3-1 Front Panel of the Model 3480 Electrospray Aerosol

Generator ...................................................................... 3-

3-2 Back Panel of the Model 3480 Electrospray Aerosol

Generator ...................................................................... 3-

3-3 ANALOG OUTPUT Pin Designations.................................. 3-

3-4 Main Internal Components ............................................... 3-

4-1 Inserting a Sample Vial into the Pressure Chamber .......... 4-

4-2 Three Views of Capillary Tip Through the Viewing

Window ......................................................................... 4-

5-1 Inlet Fitting....................................................................... 5-

5-2 Viewing Window Assembly................................................ 5-

5-3 Cleaning the Electrospray Chamber.................................. 5-

5-4 Cleaning the Pressure Chamber ..................................... 5-

5-5 Removing or Installing the Capillary ............................... 5-

5-6 Determination of High-Voltage Polarity ........................... 5-

5-7 Reversing the High Voltage Polarity ................................ 5-

B-1 Schematic Diagram of the Electrospray ............................ B-

B-2 Bipolar Particle Charge Distribution in Air

[Wiedensohler and Fissan, 1988] ................................... B-

B-3 Electrospray Flow Schematic............................................ B-

2

4
5
7

6

7

3
5

7
11
13
17
18

2

5

8

Contents ix

Tables

2-1 Electrospray Packing List ................................................. 2-1

3-1 Signal Connections for Analog Output Configurations ...... 3-

4-1 Selected Proteins and Their Diameters.............................. 4-

5-1 Maintenance Schedule...................................................... 5-

5-2 Replacement Parts.......................................................... 5-

6-1 Troubleshooting if the Electrospray Operation is

Unstable........................................................................ 6-

6-2 Troubleshooting if the Capillary has Become Plugged ....... 6-

A-1 Specifications of the Model 3480 Electrospray Aerosol

Generator ...................................................................... 8-

B-1 Capillary Flow Characteristics for Water at 20°C .............. B-

B-2 Midpoint Particle Diameters and Fraction of Total

Particle Concentration that Carries +1, +2, +3, and

+4 Elementary Charges ................................................. B-

B-3 Coefficients for Equation B-4............................................ B-

5

5

1

19

2
3

1

3

6
7

x Model 3480 Electrospray Aerosol Generator

Safety

This section gives instructions to promote safe and proper handling
of the Model 3480 Electrospray Aerosol Generator.

There are no user serviceable parts inside the instrument. Refer all
repair and maintenance to a qualified technician. All maintenance
and repair information in this manual is included for use by a
qualified technician.

To prevent problems, take these precautions:

 Do not remove any parts from the instrument unless you are

specifically told to do so in this manual.

 Do not remove the instrument housing or covers while power is

supplied to the instrument.

Caution

Labels

!

If the Model 3480 is used in a manner not specified by the manufacturer,
the protection provided by the equipment may be impaired.

WARNING

High voltage is accessible in several locations within this instrument.
Make sure you unplug the power source before removing the cover or
performing maintenance procedures.

The Electrospray has the eight labels shown in Figure S-1. They are
described below starting from the bottom-right and moving
clockwise.

1. High-Voltage Symbol Label (interior, on high-voltage power

supply shield)

2. High-Voltage Symbol Label (interior, on power supply)

3. High-Voltage Symbol Label (interior, on power entry module)

4. Ground Symbol Label (interior, bottom, next to ground stud)

5. Caution, No User Serviceable Parts… Label (back of cabinet)

xi

6. Customer Service Label (back of cabinet)

7. Serial Number Label (back of cabinet)

8. High-Voltage Symbol Label (interior, on high-voltage fitting

shield)

Figure S-1
Location of Warning and Information Labels

Description of Caution/Warning Symbols

The following symbol and an appropriate caution statement are
used throughout the manual and on the Model 3480 to draw
attention to any steps that require you to take cautionary measures
when working with the Model 3480:

Caution

Caution

Caution means be careful. It means if you do not follow the procedures

!

prescribed in this manual you may do something that might result in
equipment damage, or you might have to take something apart and start
over again. It also indicates that important information about the operation
and maintenance of this instrument is included.

xii Model 3480 Electrospray Aerosol Generator

!

Warning

WARNING

Warning means that unsafe use of the instrument could result in serious
injury to you or cause irrevocable damage to the instrument. Follow the
procedures prescribed in this manual to use the instrument safely.

Caution or Warning Symbols

The following symbols may accompany cautions and warnings to
indicate the nature and consequences of hazards:

Warns you that uninsulated voltage within the instrument may
have sufficient magnitude to cause electric shock. Therefore,
it is dangerous to make any contact with any part inside the
instrument.

Warns you that the instrument is susceptible to electro-static
dissipation (ESD) and ESD protection procedures should be
followed to avoid damage.

Indicates the connector is connected to earth ground and
cabinet ground.

Radiation Safety

The Electrospray Aerosol Generator contains a Model P-2042
Nuclespot Local Air Ionizer with a Polonium-210 source. Under
normal circumstances, you will not come into contact with
hazardous radiation. However, take these precautions when
operating the Electrospray:

Warns you that the Model P-2042 Nuclespot Local Air
Ionizer, which is installed inside the Model 3480 Electrospray
Aerosol Generator, contains Polonium-210, a radioactive
material that is subject to the regulations of the U.S. Nuclear
Regulatory Commission and local regulations. Carefully read
the Model P-2042 Literature provided with the ionizer to
determine your legal responsibilities regarding the ionizer.

Safety xiii

The Model P-2042 Nuclespot Local Air Ionizer with a Polonium-210
source must be installed in the Electrospray for it to operate properly.
Po-210 is subject to the regulations of the U.S. Nuclear Regulatory
Commission and local regulations. Carefully read the safety information
provided with the ionizer to determine your legal responsibilities regarding
the ionizer.

WARNING

The use of controls, adjustments, or procedures other than those
specified in this manual may result in exposure to hazardous radiation.

 Corrosive materials can degrade the protective coating of gold

on the ionizer inside the Electrospray. Do not operate the
Aerosol Generator with chemicals that corrode gold.

 Do not operate the Aerosol Generator at temperatures above

50°C. Excess temperatures may damage the ionizer, resulting in
radioactive contamination.

 The ionizer must be returned after 12 months. Contact TSI for

information and instructions on returning the ionizer.

 Do not remove any parts from the Electrospray unless you are

specifically told to do so in this manual.

Chemical Safety

Observe these warnings when operating the Electrospray Aerosol
Generator:

Any material or procedure mentioned in this manual is intended for use by

!

!

qualified professionals familiar with potential chemical hazards and
trained in safe laboratory procedures.

Corrosive materials can degrade the stainless steel and aluminum
chamber inside the Electrospray Aerosol Generator. Do not operate the
Electrospray with chemicals that corrode stainless steel or aluminum.

WARNING

WARNING

xiv Model 3480 Electrospray Aerosol Generator

High concentrations of aerosols can be hazardous. Use a filter at the

!

Electrospray exit if the generated aerosol is not being used by another
instrument or in another application.

Electrical Safety

The Electrospray Aerosol Generator contains a high-voltage source
on the inside of the instrument. Under normal circumstances, you
will not come into contact with hazardous voltage. However, always
remove power from the Electrospray before removing the cover from
the instrument.

High voltage is accessible in several locations within this instrument.
Make sure you unplug the power source before removing the cover or
performing maintenance procedures.

WARNING

WARNING

Safety xv

About This Manual

Purpose

This is an instruction manual for the operation and handling of the
Model 3480 Electrospray Aerosol Generator.

Related Product Literature

 Model 3080 Electrostatic Classifier Manual (part number

1933792 TSI Incorporated)

Getting Help

 Model 3010 Condensation Particle Counter Manual (part number

1933010 TSI Incorporated)

 Model 3022A Condensation Particle Counter Manual (part

number 1933763 TSI Incorporated)

 Model 3025A Ultrafine Condensation Particle Counter Manual

(part number 1933762 TSI Incorporated)

 Model 3936 SMPS (Scanning Mobility Particle Sizer) Manual (part

number 1933796 TSI Incorporated)

 Model 3068 Aerosol Electrometer Manual (part number 1933068

TSI Incorporated)

To obtain assistance with this product or to submit suggestions,
please contact TSI:

TSI Incorporated
500 Cardigan Road
Shoreview, MN 55126 U.S.A.
Fax: [phone]
Telephone: [phone] (USA) or [phone]
E-mail Address:

[e-mail]

xvii

Submitting Comments

TSI values your comments and suggestions on this manual. Please
use the comment sheet, on the last page of this manual, to send us
your opinion on the manual’s usability, to suggest specific
improvements, or to report any technical errors.

If the comment sheet has already been used, send your comments
to:

TSI Incorporated
500 Cardigan Road
Shoreview, MN 55126 U.S.A.
Fax: [phone]
E-mail Address: [e-mail]

xviii Model 3480 Electrospray Aerosol Generator

CHAPTER 1

Product Overview

This chapter describes the Model 3480 Electrospray Aerosol
Generator and gives an overview of how it works.

Product Description

The Model 3480 Electrospray Aerosol Generator, shown in
Figure 1-1, generates monodisperse aerosols in the size range of 2
to 100 nanometers. Beginning with a liquid and adding a solute to
form a solution or suspension, the Electrospray converts the
sample to an aerosol by charging the liquid, pushing it through a
capillary, and exerting an electric field at the capillary tip. The
liquid evaporates from the droplets formed at the capillary tip while
the charge on each droplet is reduced by an ionizer.

In addition to the vast combination of solutes that could be used in
the Electrospray to generate aerosols, the user has the ability to
control the liquid flow rate through the capillary, the intensity of
the electric field at the capillary tip, and the amount of time the
aerosol is exposed to the ionizer.

Figure 1-1
Model 3480 Electrospray Aerosol Generator

1-1

Applications

The successful use of the electrospray method to generate
monodisperse aerosol has been documented in many publications.
Although the basic principles are well understood, many of the
details explaining how different operating parameters affect the
electrospray method remain to be discovered. Known applications
for this instrument include:

 Studies of nano-aerosols

 Instrument calibration

 Dispersion of nanometer-sized powders for nano-powder sizing

 Aerosol analysis in the macromolecular and submicrometer

range

 Research involving parameters that influence the electrospray

method

How the Electrospray Operates

A sample solution is stored in a cone-shaped vial, enclosed in a
cylindrical pressure chamber. The chamber accommodates a
capillary and a high-voltage, platinum wire, both of which are
immersed in the solution. A differential pressure causes the
solution to be pushed through the capillary.

An electrical field pulls the charged solution out of the capillary
exit, forming droplets that are mixed with clean air and CO

. This

2

produces a sheath flow, which transports the droplets to the
Electrospray chamber. The highly charged droplets are neutralized
by a radioactive ionizer (Polonium-210), and the liquid is
evaporated before the aerosol exits the instrument.

1-2 Model 3480 Electrospray Aerosol Generator

Packing List

CHAPTER 2

Unpacking and Setting
Up the System

Use this information in this chapter to unpack and set up the
Model 3480 Electrospray Aerosol Generator.

As you unpack the shipping container, make certain the shipment
is complete. Table 2-1 gives a packing list for the Electrospray.

Table 2-1
Electrospray Packing List

Qty Description Part No.

1 Model 3480 Electrospray Aerosol Generator 348000
1 Electrospray Accessory Kit Including:
1 pkg. Capillaries 25 µm (25 per pack) 3900124
1 Ionizer Retainer Tool 3012062
1 Tee Connector with Filter 1030023
1 L-Key Hex Wrench (.050 in) 3305003
1 Cable, Power Supply 1303053*
1 Instruction Manual 1933793
2 Ferrules, Nylon Front (1⁄16-in tube) 1611252
2 Ferrules, Nylon Back (1⁄16-in tube) 1611253
2 O-rings, 1-009 (FSI) 2501899
6 O-rings, 1-010 (EPDM) 2501520
2 O-rings, 1-013 (FSI) 2501567
2 O-rings, 1-014 (EPDM) 2501528
2 O-rings, 1-016 (EPDM) 2501602
2 O-rings, 1-020 (EPDM) 2501073
2 O-rings, 1-024 (BUNA) 2501024
2 O-rings, 1-027 (EPDM) 2501603
2 O-rings, 1-029 (EPDM) 2501072
1 Vacuum Grease 1101063
50 Vial, 1.5 ml Center Tube Poly 3002003
5 ft [1.5 m] Tubing, Silicone Conductive 3⁄8-in OD 3001903
10 ft [3 m] Tubing, Polyethylene ¼-in OD 3929436

*Power cable listed is for U.S.A. use only.

Note: A Polonium-210 ionizer is shipped separately from the

Electrospray instrument and accessory kit. The ionizer must
be installed for the Electrospray to operate properly. See the
instructions later in this chapter for installing the ionizer.

2–1

Mounting the Instrument

The Electrospray has no special mounting requirements other than
providing good ventilation (see below). The cabinet has four non­marking rubber feet that give the instrument a good grip on clean,
level surfaces. The rubber feet (Figure 2-1) are installed in the
cabinet using integrated #8-32 UNC threaded fasteners and can be
removed (by unscrewing) to allow other mounting fasteners to be
used.

Note: If the cabinet is mounted to a plate, drill holes in the plate to

match the ventilation holes in the bottom of the cabinet or use
standoffs to raise the bottom of the cabinet at least ½ inch
(1.2 cm) above the mounting plate.

1.50 [38,1]

7.99 [202,8]

10.50 [266,7]

15.86 [402,8]

Figure 2-1
Bottom View of Electrospray Aerosol Generator Showing Location of Rubber Feet.
Feet can be removed to provide mounting points on cabinet. Dimensions are in
inches [mm].

.68 [17,3]

.59 [15,0]

6.00 [152,4]

Ventilation Requirements

The Electrospray cabinet is designed to be cooled by natural
convection of room air drawn through the bottom of the cabinet and
exhausted through the back of the cabinet.

The cabinet should be installed with at least 2-inch (50 mm)
clearance between the back panel and any other surface. Also, the
cabinet should be set on a clean, hard surface so that the intake air
can move freely under the base of the cabinet.

2–2 Model 3480 Electrospray Aerosol Generator

Checking the Zero of the Pressure Gauge

The pressure gauge is adjusted to the zero position at the factory;
however, if the needle is not lined up with the left side of the zero
box marked on the gauge, you will need to re-zero the pressure
gauge (see Figure 3-1).

If zeroing is required, follow the steps below to reset the gauge:

1. You will need a palm-sized square of soft, clean rubber to grip

the front surface of the gauge and a .050 inch hex wrench
(included in the accessory kit).

2. Hold the cabinet for support and grip the front surface of the

gauge with the square of rubber in the palm of your hand.

3. Unscrew the front cover of the gauge in a counter-clockwise

direction.

4. A sockethead setscrew is located under the bottom of the gauge

panel where it is marked “zero”.

5. Adjust the setscrew until the needle lines up with the left side of

the zero box marked on the gauge.

6. Reassemble the front cover of the gauge.

Power Connection

Connect the AC power cord (supplied) to the AC POWER IN
connection on the back of the Electrospray and then into an
available power outlet. It is not necessary to select the correct
voltage, the instrument accepts line voltages of 85 to 260 VAC,
50-60 Hz, 25 W max., single phase. The connector has a built-in
on/off switch.

Note: Make certain the line cord is plugged into a grounded (earth

grounded) power outlet. Position the Electrospray so the power
cord connector is not blocked and is easily accessible.

Note: The Electrospray power supply contains no user-serviceable

parts. If the power supply is not operating correctly, use the
information in
not be used in a manner not specified by the manufacturer.

Toggle the on/off switch at the AC POWER IN connection to the on
position to verify the instrument has power.

Chapter 7 to contact TSI. This instrument should

Unpacking and Setting Up the System 2–3

Analog Output

The Electrospray has a single 15-pin, D-subminiature connector
port on the back panel labeled ANALOG OUTPUT that can be used
to measure signals that represent the voltage and current output
on the front panel meters of the instrument. See
detailed list of the signal connections.

Filtered Air Input

The back panel of the Electrospray has an input marked FILTERED
AIR IN, 25 PSI MAX that is a ¼” Swagelok
ferrules. Insert the supplied polyethylene tubing or a similar tubing
and tighten the Swagelok® nut finger-tight plus ¼-turn with a
wrench. This will provide a secure connection and allow the tubing
to be removed without damaging the ferrules. A regulated,
compressed air supply that furnishes HEPA-filtered, clean, dry air
must be used to supply filtered air to the Electrospray. TSI
Model 3074B Filtered Air Supply is recommended and may be
purchased separately. The recommended pressure of the filtered air
supply used with the Electrospray is 15 psi.

®

WARNING

Chapter 3 for a

tube fitting with nylon

Supplying more than 25 PSI air pressure could result in damage to the

!

internal components of the Electrospray and decreased sensitivity of the
pressure regulator and air rotameter.

CO2 Input

Above the filtered air input, is an identical input marked CO2 IN,
15 PSI MAX. Connect the supplied polyethylene tubing in the
manner described for the Filtered Air Input, using a commercial
CO

compressed gas tank to supply CO2 to the Electrospray.

2

Commercial CO
compressed gas suppliers, in denominations ranging from 2.5 to
50 lb. The recommended pressure of the CO
Electrospray is 5 psi.

®

Swagelok is a registered trademark of Swagelok Company.

tanks and accessories are available from most

2

supply used with the

2

2–4 Model 3480 Electrospray Aerosol Generator

Supplying more than 15 PSI CO2 pressure will cause the internal silicone

!

tubing to disconnect from the CO
CO

inlet pressure makes it more difficult to adjust the CO2 flow rate.

2

Installing the Ionizer

A Model P-2042 Nuclespot Local Air Ionizer with a Polonium-210
source is shipped separately because of regulations that govern
packaging and shipping requirements for radioactive materials. The
ionizer must be installed for the Electrospray to operate properly.
Before installing the ionizer, read the safety information at the
beginning of this manual and the safety information provided with
the ionizer.

The use of controls, adjustments, or procedures other than those
specified in this manual may result in exposure to hazardous radiation.

Use this procedure to install the ionizer:

WARNING

rotameter fitting. In addition, a higher

2

WARNING

1. Remove the ionizer retainer shown in Figure 2-2 using the

ionizer retainer tool supplied in the accessory kit, and set the
dummy source aside.

2. Place the ionizer in the ionizer retainer in place of the dummy

source. The ionizer mesh-side should be facing the open end of
the ionizer retainer.

3. Install the ionizer retainer, making sure the O-ring is between

the ionization chamber and the ionizer retainer, and tighten
with the ionizer retainer tool.

Note: The ionizer must be replaced 12 months from the date on the

ionizer label. Contact TSI to order a new ionizer four weeks
before the ionizer expiration date. When returning an ionizer,
contact TSI for handling and shipping instructions.

Unpacking and Setting Up the System 2–5

Figure 2-2
Installing the Ionizer

Ionization
Chamber

Dummy Source

O-Ring (2501027)

Ionizer Retainer

2–6 Model 3480 Electrospray Aerosol Generator

CHAPTER 3

Controls, Indicators,
and Connectors

Use the information in this chapter to familiarize yourself with the
location and function of controls, indicators, and connectors on the
Model 3480 Electrospray Aerosol Generator.

This chapter is organized into three sections describing aspects of
the instrument: Front Panel, Back Panel, and Internal Components.

Front Panel

The main components of the front panel are shown in Figure 3-1.
They include: the voltage and current LED displays, the voltage
adjustment knob, the power and high-voltage LED indicators, the
CO

and air rotameters, the pressure regulator and gauge, and the

2

pressure chamber. In addition, the viewing window and ionizer
retainer are integrated with the cover and are included in this
section.

LED Displays

There are two LED displays on the Model 3480: Voltage (kV) and
Current (nA).

 The voltage LED display is a measure of the high voltage applied

to the platinum wire, which charges the liquid in the vial and
capillary. A positive high voltage is standard, but a negative
high-voltage module is available in place of or in addition to the
positive high-voltage module.

 The current LED display is a measure of the status and stability

of the Electrospray Aerosol Generator. See Chapter 4,
“

Operating the Electrospray” for more information on how the

current reading aids in determining the status of the
Electrospray, and Appendix B, “
detail on how the current is measured.

Theory of Operation” for more

3–1

Current LED Display

A

Voltage LED Display

Power LED Indicator

High Voltage LED Indicator

Voltage Adjustm ent Knob

Voltage Adjustment Knob

This knob is used to change the high voltage applied to the liquid
used in the electrospray process. It can be locked by pushing the
black tab clockwise on the base of the knob.

Viewing Window

Ionizer Retainer

CO

Rotameter

2

ir Rotameter

Pressure Chamber

Pressure Regulator

Pressure Gauge

Figure 3-1
Front Panel of the Model 3480 Electrospray Aerosol Generator

Indicators

There are two status LED’s on the Electrospray: power and high
voltage.

 The green power LED indicates that power is supplied to the

instrument.

 The high-voltage LED indicates that high voltage is being

applied to the platinum wire. The high voltage is turned off if
the cover is off the instrument or the bottom half of the
pressure chamber is not installed.

3–2 Model 3480 Electrospray Aerosol Generator

Rotameters

The rotameters regulate the flow rates of air and CO2 to the
Electrospray chamber. The air and CO
and 0.1 L/min, respectively.

flow rates are typically 1.0

2

Pressure Regulator and Gauge

The pressure drop across the capillary is regulated and measured
with these two components. See Appendix B, “
for details on how the pressure drop is measured and how it can be
used to approximate the flow rate of the liquid through the
capillary.

Theory of Operation”

Pressure Chamber

The pressure chamber holds a sample vial, which contains the
liquid solution to be electrosprayed. A platinum wire and capillary
extend from the top half of the pressure chamber into the liquid
solution to charge and transport the liquid solution, respectively.
To change the sample vial, the bottom half of the pressure chamber
can be removed by twisting
is not supplied to the platinum wire if the bottom half of the
pressure chamber is removed. In addition, an in-line orifice
provides a pressure drop equal to the differential pressure set
point, eliminating the need to reduce the pressure when changing
samples. See Chapter 4, “
instructions for handling or changing the sample vial.

1

⁄8-turn counterclockwise. High voltage

Operating the Electrospray” for detailed

Viewing Window

The viewing window provides a visual inspection of the capillary tip.
This is useful when observing the different operating modes of the
Electrospray and when installing a capillary. It is also a good tool
for troubleshooting the Electrospray. The viewing window is backlit
by a green LED and the lens can be adjusted to focus on the
capillary tip by rotating the lens mount.

Ionizer Retainer

The ionizer retainer allows a Model P-2042 Polonium-210
radioactive ionizer to be installed in the Electrospray chamber to
meet all radiation safety requirements. The ionizer reduces the
charge on the droplets produced by the Electrospray to increase the
exit aerosol concentration.

Controls, Indicators, and Connectors 3–3

Back Panel

Aerosol Exit

As shown in Figure 3-2, the back panel has power and data
connections, as well as air and CO

inlets and the aerosol exit.

2

CO2 Inlet

Filtered Air Inlet

Analog Output

AC Power Connector

Figure 3-2

Back Panel of the Model 3480 Electrospray Aerosol Generator

Aerosol Exit

Flexible tubing with a diameter slightly less than ¼” or any ¼”
Swagelok®-type fitting can be attached to the aerosol exit.
Conductive tubing is supplied for use at the aerosol exit to
minimize particle loss due to electrostatic charge.

3–4 Model 3480 Electrospray Aerosol Generator

Analog Output

The analog output is a standard 15-pin D-sub connection that
allows analog signals to be read by an external instrument to
collect Electrospray voltage and current information. The pin
designations and signal connections are shown in Figure 3-3 and
Table 3-1, respectively. Note the conversion factors in Table 3-1.

876

15

Figure 3-3
ANALOG OUTPUT Pin Designations

Table 3-1

Signal Connections for Analog Output Configurations

Pin Number(s) Signal

1 Voltage Output (1V = 1.00 kV)
2 Voltage GND
3 Current Output (1V = 100 nA)
4 Current GND
5-15 —

54321

1011121314

9

AC Power Connector

The AC power connector accepts the line cord (supplied) to provide
AC power to the instrument. Line voltage can be 85 to 260 VAC,
50/60 Hz, single phase, 3A max. The connector has a built-in
on/off switch. Power consumption is 25 Watts, max.

Note: Make certain the line cord is plugged into a grounded power

outlet. Position the Electrospray so the power cord connector is
easily accessible.

Filtered Air Inlet

The filtered air inlet connection is described in Chapter 2,
“

Unpacking and Setting Up the System.”

CO2 Inlet

The CO2 inlet connection is described in Chapter 2, “Unpacking and

Setting Up the System.”

Controls, Indicators, and Connectors 3–5

Internal Components

The main internal components are shown in Figure 3-4. A brief
description of each follows.

Capillary

The capillary transports the liquid to be electrosprayed from the
sample vial to the Electrospray chamber. More information on the
liquid flow through a capillary can be found in Appendix B, “

of Operation.” Information on the maintenance of the capillary can

be found in Chapter 5, “

Electrospray Chamber

The aerosol is generated inside the Electrospray chamber. See
Chapter 5, “
maintain the Electrospray chamber. Appendix B, “

Operation” contains information on the theory of operation of the

Electrospray chamber.

High-Voltage Fitting and Shield

Maintenance” for instructions on how to clean and

Theory

Maintenance.”

Theory of

The high-voltage fitting is attached to the top half of the pressure
vessel. High voltage is supplied to the fitting, which is connected to
a platinum high-voltage wire that is immersed in the liquid
contained in the sample vial, hence charging the liquid. The high­voltage shield covers the high-voltage fitting to protect the user
from accidental electrical shock.

3–6 Model 3480 Electrospray Aerosol Generator

Interlock Switch

Power Supply

Filters (4)

Electrospray
Chamber

Capillary Sleeve

Capillary

High Voltage
Fitting and Shield

Main PCB

High Voltage
Supply Module

Figure 3-4
Main Internal Components

Power Supply

15V is supplied to the main PCB by the 25W power supply. The
power supply contains no user serviceable parts.

Main PCB

Controls all the electronics in the Electrospray. This PCB is
calibrated at the factory and there should be no need to make
adjustments to its components under normal usage.

High-Voltage Supply Module

The high voltage supplied to the Electrospray chamber is generated
by this component. Two modules are available: positive high voltage

Controls, Indicators, and Connectors 3–7

(standard) and negative high voltage. See Chapter 5 for instructions
on servicing the high-voltage supply module.

Interlock Switch

The interlock switch is a safety measure to ensure that high voltage
will not be supplied to any part of the instrument unless the
instrument cover is in its proper position.

Filters

These filters are used to clean the air and CO2 in various flow paths
in the instrument. See Appendix B, “
schematic of the Electrospray and see Chapter 5, “
information related to the maintenance of these filters.

Theory of Operation” for a flow

Maintenance” for

3–8 Model 3480 Electrospray Aerosol Generator

CHAPTER 4

Operating the
Electrospray

Use the information in this chapter to become familiar with how to
prepare liquid solutions and operate the Model 3480 Electrospray
Aerosol Generator.

Preparing Samples

Samples can be prepared and stored using commercially available
materials, handling procedures, and storage equipment. Typically,
a buffer solution is made, the conductivity and pH are adjusted,
and a solid or nonvolatile liquid is dissolved in the buffer solution.
You may find it most convenient to prepare a large (500 mL) buffer
solution adjusted to the desired conductivity and pH, and then
dilute sample material with the buffer solution in a standard
sample vial (1.7 mL centrifuge tube).

WARNING

!

!

Any material or procedure mentioned in this manual is intended for use
by qualified professionals familiar with potential chemical hazards and
trained in safe laboratory procedures.

Caution

To slow the growth of contaminants in a buffer solution or sample
solution, refrigerate them when not in use. In addition, use caution when
handling sample vials to avoid transferring contaminants to the vial.

4–1

Preparing a Buffer Solution

A buffer solution is intended for use in the Electrospray to clean the
capillary either before, after, or between samples. It is also useful to
use a buffer solution as the solvent to dissolve solids or nonvolatile
liquids when preparing samples. Key guidelines for choosing a
buffer solution include the following:

 volatile solution—the solution must evaporate in the

Electrospray chamber

 chemical buffer—the pH of the solution should not change

significantly when a sample is made

 adjustable pH—when making certain samples, such as

proteins, the pH value of the solution must be greater than the
isoelectric point (pI value) for the protein or the sample will stick
to the capillary walls

 adjustable conductivity—the primary droplet size produced by

the Electrospray is inversely proportional to the cube root of the
conductivity, therefore, there is a finite range of conductivities
over which the Electrospray will operate

A buffer solution used extensively in the Electrospray is 20 mM
ammonium acetate created by dissolving ammonium acetate in
ultrapure water. De-ionized water can be used in place of ultrapure
water if necessary; however, ultrapure water is recommended to
reduce the chances of buffer or sample contamination growth.
20 mM ammonium acetate is volatile, a weak buffer, and has an
adjustable pH and conductivity.

As an example to get started using the Electrospray, a 20 mM
ammonium acetate buffer solution with a conductivity of 0.2 S/m
adjusted to pH 8 is useful for dissolving solutes such as sucrose,
PSL, and proteins, to name a few. The procedure for making this
buffer solution (subsequently referred to as the standard buffer
solution) is outlined here:

1. Dissolve 0.77 grams of ammonium acetate in 500 milliliters of

ultrapure or de-ionized water.

2. Assuming the solution has an initial pH of 6.7, add 0.75

milliliters of 1M ammonium hydroxide.

3. See the following sections for measurement and adjustment of

the buffer solution conductivity and pH.

Measuring and Adjusting Conductivity

A conductivity meter is useful for measuring the conductivity of a
buffer solution. The conductivity can be increased or decreased by
adding ammonium acetate or ultrapure water, respectively, to the
buffer solution. Although the Electrospray will operate at a wide

4–2 Model 3480 Electrospray Aerosol Generator

range of conductivities, a 0.2 S/m buffer solution is typically used.
An experimental analysis of the useful range of liquid conductivity
as a function of liquid flow rate using an electrospray method is
discussed in the following journal article:

Chen, Da-Ren, David Y.H. Pui, and Stanley L. Kaufman [1995]
“Electrospraying of Conducting Liquids for Monodisperse Aerosol
Generation in the 4 nm to 1.8 µm Diameter Range.”
J. Aerosol Sci., 26:963-977.

Measuring and Adjusting pH

A pH meter is useful for measuring the pH of a buffer solution.
Ammonium hydroxide or acetic acid can be added to the buffer
solution to increase or decrease the pH value, respectively. Since
the pH value should be greater than the pI value for proteins, a
useful reference for pI values of selected proteins is:

Righetti, P.G., G. Tudor, and K. Ek [1981]
“Isoelectric Points and Molecular Weights of Proteins: A New Table.”
Chromatographic Reviews 149, J. Chromatography, 220:115-194.

Typical Solutes

Any solid or nonvolatile liquid that is soluble in a buffer solution
can be used to make a sample for use with the Electrospray. With a
standard buffer solution, useful solutes include sucrose, PSL, and
proteins. The properties of each solute and methods of preparing
each sample are discussed below.

Sucrose

The sucrose concentration of a sample can be varied to create
continuously variable particle sizes. For a given conductivity and
flow rate, the diameter of the primary droplets produced by the
Electrospray will remain the same. Once the liquid evaporates from
the primary droplet, the sucrose contained within the volume of the
primary droplet will determine the resulting particle diameter.

The resulting particle diameter D
formula D

= 150 (ϕ)

p

1/3

, where 150 being the primary droplet size1 in
nm and ϕ being the sucrose volume fraction per unit volume buffer.
For example, at ϕ = 0.1 (10% volume sucrose per unit volume
buffer), the resulting particle diameter will be 69 nm. At ϕ = 0.001,
the particle diameter will be 15 nm. The maximum particle
diameter that may be created is 78 nm at ϕ = 0.143 reflecting
smaller droplet sizes at higher concentrations.

1

The viscosity of sucrose solutions may vary by concentration, influencing the flow rate and, thereby, the primary

droplet size. Refer to Morison (2002) for more information.

may be calculated using the

p

Operating the Electrospray 4–3

Sucrose solutions can be made using the following method:

1. Dissolve 1.58 grams sucrose per 10 milliliters buffer to make a

10% V/V solution.

2. For lower concentrations of sucrose, dilute the 10% V/V

solution with buffer solution accordingly.

Ken R. Morison, Department of Chemical and Process Engineering,
University of Canterbury, Christchurch, New Zealand. “Viscosity
Equations for Sucrose Solutions: Old and New,” Paper #984 The

Asian Pacific Confederation of Chemical Engineering (APCChE)
Conference [2002].

PSL (Polystyrene-Latex)

PSL is used to generate test aerosols in a wide size range, from
20 nm to 160 µm—the Electrospray is useful on the low end of this
range, from 20 to 100 nm. PSL is commercially available as
aqueous suspensions in 15 mL dropper bottles, and samples can
be easily made by adding one drop (50µL) of PSL to 1 mL of buffer
solution in a standard sample vial. Unlike sucrose, PSL size is
independent of concentration. Higher aerosol concentrations can be
obtained by adding more PSL, which may become necessary with
larger PSL sizes.

Proteins

!

Most proteins that have been used with the Electrospray range
from 3 to 12 nm in diameter. Most are commercially available from
many chemical companies. The diameters of particles generated
from proteins are independent of sample concentration. Protein
samples can be prepared using the following method:

1. Dissolve 1 mg protein per 1 milliliter buffer solution.

2. Dilute the 1mg/mL solution to obtain a 10 µg/mL solution.

This concentration is sufficient for most proteins when
analyzing the size distribution of the protein aerosol.

Selected proteins and their diameters are listed in Table 4-1. This is
a very limited sample of the numerous proteins available.

Caution

Some proteins may be dangerous to emit into the environment. Filter
dangerous aerosols before emitting them into the environment.

4–4 Model 3480 Electrospray Aerosol Generator

Table 4-1

Selected Proteins and Their Diameters

Protein Diameter (nm)

Ubiquitin 3
Bovine Serum Albumin 6.5
Ferritin 12

Starting Up the Electrospray

After the Electrospray system has been set up (see Chapter 2,
“

Unpacking and Setting Up the System”) and samples have been

made, follow this procedure to begin generating aerosols:

1. Turn on the power switch on the back panel. Make sure the

power and high-voltage LED’s are on and check the viewing
window to make sure the capillary tip is near the center of the
viewing window.

2. Remove the bottom half of the pressure chamber by twisting it

1

⁄8-turn counterclockwise. The bottom half can then be removed

by pulling downward.

!

Note: High voltage is turned off if the bottom half of the pressure

chamber is removed.

3. Insert and open the sample vial as shown in Figure 4-1. Use

caution not to contaminate the sample.

4. Replace the bottom half of the pressure chamber by aligning the

grooves to the pins in the top half and pushing the bottom half
upwards, making sure the capillary and platinum wire are
aligned with the sample vial. As the pins enter the grooves,
continue pushing upwards while turning the bottom half
clockwise until the bottom half locks in place.

WARNING

The capillary and platinum wire are adjusted for use with a 1.7 mL
centrifuge tube, if it is necessary to use a different sized vial, see
Chapter 5, “
platinum wire positions to avoid breaking the capillary or damaging the
platinum wire.

Maintenance” for instructions on adjusting the capillary and

Operating the Electrospray 4–5

Sample Vial

Pressure Chamber
Bottom Half

Figure 4-1

Inserting a Sample Vial into the Pressure Chamber

5. Turn the pressure regulator knob clockwise until the pressure

gauge reads 3.7 psi.

6. Turn the air rotameter knob counterclockwise to reach

1.0 L/min.

7. Turn the CO

0.1 L/min.

8. Turn the voltage adjustment knob clockwise to reach 2.30 kV.

9. Within two minutes the liquid should be exiting the capillary.

See Chapter 6, “
through the capillary after two minutes.

Generating Aerosols

The Electrospray operating parameters set in the “Starting Up the

Electrospray” section should result in a stable generation of aerosol

in the Cone-Jet mode of the Electrospray (see below for an
explanation of the “Cone-Jet” mode). Once the liquid is flowing from
the capillary tip, the high voltage can be adjusted to achieve
different Electrospray operating modes. Four distinct modes (see
Figure 4-2) can be observed through the viewing window or by the
current LED display as the electric field is increased by increasing
the high voltage: Dripping mode, Pulsating mode, Cone-Jet mode,

rotameter knob counterclockwise to reach

2

Troubleshooting” if the liquid has not made it

4–6 Model 3480 Electrospray Aerosol Generator

and Corona Discharge mode. Figure 4-2 shows three photographs
of the capillary tip viewed through the viewing window.

Figure 4-2

Three Views of Capillary Tip Through the Viewing Window: (1) No liquid flow, (2)
Liquid flow but no electric field (Dripping mode), (3) Liquid flow and an electric field
(Cone-Jet mode). The third view illustrates stable electrospray operation.

 Dripping mode (view 2 in Figure 4-2) occurs when a primary

droplet builds up on the end of the capillary until it becomes
large enough to be pulled away by the weak electric field. The
current display is usually near zero in this mode. Inspection
through the viewing window shows the primary droplet
increasing in size until it is pulled away at a very low frequency.
As the voltage is increased in this mode, the primary droplet
size decreases.

 In Pulsating mode, the liquid at the tip of the capillary

continues to drip, but at a higher frequency than in dripping
mode. In addition, a visual inspection shows a more cylindrical
liquid profile with a cone-shaped tip. During operation, the
cylindrical liquid profile increases in length and the current
display increases until the primary droplet is pulled away (and
the current display rapidly decreases). As in the dripping mode,
as the voltage is increased, the primary droplet size decreases
while the frequency increases.

 The Cone-Jet mode (view 3 in Figure 4-2) occurs when the

electric field strength is balanced with the liquid properties. A
visual inspection shows the conical shape of the profile (Taylor
Cone), but the jet of primary droplets cannot be seen since the
primary droplets are very small. As voltage is increased, the
profile does not change significantly while in this mode; in
addition, the total current reading changes very little. The cone­jet mode is the most stable and useful mode for generating
aerosols. The voltage setting in this mode is typically 2.00 to

2.50 kV using a 20 mM ammonium acetate buffer solution.

 As the voltage is increased further, the electric field becomes too

strong for the liquid and surrounding gas and the Corona
Discharge mode occurs. The strong electric field causes the tip

of the liquid to become rounded. Also, the current reading is
high because of the current traveling through the CO

/air

2

sheath flow, and erratic because of the instability of this mode.

Operating the Electrospray 4–7

Changing Samples

Caution must be used when changing samples to avoid
contaminating either of the samples. A buffer solution should be
run in the Electrospray between samples to clear the capillary of
possible contaminants. Follow the procedure below (see “

Up the Electrospray” earlier in this chapter for details) to change

samples.

To avoid contaminating samples, a buffer solution should be run between

!

samples to clear the capillary of possible contaminants.

1. Remove the bottom half of the pressure chamber.

2. Close the lid of the vial and remove it.

3. Insert a vial containing buffer solution.

4. Replace the bottom half of the pressure chamber.

Starting

Caution

5. Run buffer solution for one minute.

Note: The residence time in a capillary using a standard buffer

solution at 3.7 psi is approximately 112 seconds. For most
applications, running a buffer solution for 60 seconds will
sufficiently prevent sample contamination; however, using a
highly viscous fluid or a low capillary pressure drop will
increase the residence time. See Appendix B, “

Operation” for an analysis of liquid flow in the capillary.

6. Repeat steps 1–4, using a sample vial rather than a buffer

solution.

7. Aerosol should be produced after a time equal to the residence

time of the particular sample and operating conditions.

Shutting Down the Electrospray

The capillary should be cleaned and cleared of liquid before
shutting down the Electrospray to avoid deposits on the inside of
the capillary. Follow the procedure below (see “

Electrospray” for details) to shut down the Electrospray.

Theory of

Starting Up the

4–8 Model 3480 Electrospray Aerosol Generator

!

Caution

Buffer should be run before shutting down the Electrospray to clean the
capillary. Subsequently, the Electrospray should be run without a sample
to allow the air to clear the capillary of liquid. Follow the procedure in this
section to prolong capillary life and to avoid deposits on the inside of the
capillary.

1. Purge the capillary (see section, “

Chapter 5, “Maintenance”).

2. Remove the bottom half of the pressure chamber.

3. Close the lid of the vial and remove it.

4. Replace the bottom half of the pressure chamber without

inserting a vial to clear the liquid from the capillary and run air
through it.

5. View the capillary through the viewing window to determine

when the liquid has been cleared from the capillary. This
process takes approximately 5 minutes with a standard buffer
solution.

6. Turn the pressure regulator knob until the pressure gauge

reads zero psi.

7. Turn the air and CO

8. Turn the voltage knob counterclockwise until it reaches its

stopped position.

9. Turn the power switch off.

rotameters to read zero L/min.

2

Purging the Capillary” in

Operating the Electrospray 4–9

CHAPTER 5

Maintenance

This chapter gives maintenance and service procedures for the
Electrospray.

Periodic Maintenance

Periodic cleaning of several parts of the Electrospray is necessary to
ensure proper performance. The capillary should be cleaned after
each day’s use to prevent buildup of solutes. If aerosol deposits
accumulate on the orifice plate, the orifice could be reduced in size
or eventually plugged. In addition, aerosol deposits will buildup on
the Electrospray chamber and viewing window optics, although at a
lesser frequency than on the orifice plate. The service intervals
depend on the type and concentration of aerosols generated with
the Electrospray. The following maintenance schedule is suggested
for the Electrospray:

Table 5-1

Maintenance Schedule

Maintenance Task How Often

Purging the capillary Daily

Cleaning the orifice plate As needed

Cleaning the aerosol exit port As needed

Cleaning the viewing window lens As needed

Replacing the ionizer 12 months

Cleaning the Electrospray chamber As needed

Performing an air leak test If you clean the Electrospray

Cleaning the pressure chamber As needed

Purging the Capillary

chamber or the viewing
window lens.

The capillary should be purged after each day’s use to keep solutes
from building up on the inside of the capillary. It may need to be
purged more often depending on the chemicals you are using or if
you suspect the capillary has become partially or fully plugged (see
also page 6-

3).

5–1

!

WARNING

Any material or procedure mentioned in this manual is intended for use
by qualified professionals familiar with potential chemical hazards and
trained in safe laboratory procedures.

To purge the capillary, place one of the following solutions in a
sample vial and use it as if you were generating an aerosol (see the
section in Chapter 4, “
down the instrument, always rinse the capillary with a buffer
solution and flush the capillary with air after purging the capillary
to prevent deposits from forming on the capillary. Four different
solutions have been used with the Electrospray to purge the
capillary. They include:

 20 mM ammonium acetate buffer solution (see the section in

Chapter 4, “
use because it is the same solution recommended for use
between samples to prevent sample contamination. However,
this solution rinses the capillary but does not contain cleaning
agents. If you suspect the capillary walls are dirty, use one of
the three solutions listed below to clean the capillary and then a
buffer solution to rinse the capillary.

Preparing Samples”). This solution is convenient to

Operating the Electrospray”). When shutting

Caution

20 mM ammonium acetate buffer solution or a similar buffer solution

!

®

TWEEN is a registered trademark of Uniqema, a business unit of ICI Americas Inc.

should be run to rinse the capillary after using any detergent such as
Tween 80 or any strong alkali such as KOH to purge the capillary. After
the capillary is rinsed with the buffer solution and before turning off the
instrument, run air through the capillary to prevent deposits from forming
if the buffer solution were left in the capillary to evaporate.

 0.5% Tween

(#P8192, Sigma-Aldrich Co., St. Louis, MO) is useful if diluted
with ultrapure or distilled water to 0.5%.

 20 mM KOH solution. A 20 mM potassium hydroxide solution

in ultrapure or distilled water is a low enough concentration to
clean the capillary with little etching of the capillary walls. This
solution should not be run for more than 10 minutes because
capillary etching may become significant.

 0.1 M KOH solution. For heavy buildup, a 0.1 M potassium

hydroxide solution in ultrapure or distilled water can be used;
however, this solution should not be run for more than 2
minutes because capillary etching may become significant more
quickly than for the 20 mM KOH solution.

®

80 solution (a detergent). 10% Tween 80 solution

5–2 Model 3480 Electrospray Aerosol Generator

Cleaning the Orifice Plate

WARNING

High voltage is accessible in several locations within this instrument.
Make sure you unplug the power source before removing the cover or
performing maintenance procedures.

The orifice plate is permanently attached to the inlet fitting of the
Electrospray chamber to ensure electrical contact. Since the aerosol
is generated inside the inlet fitting and then passes through the
orifice plate, the inlet fitting will need to be cleaned more frequently
than other components through which the aerosol passes.
Figure 5-1 shows a view of the inlet fitting inside the cabinet. Use
the following steps to clean the inlet fitting and orifice plate:

Screw

Electrospray Chamber

Inlet Fitting

Capillary Sleeve

Orifice Plate

Figure 5-1

Inlet Fitting

O-Ring
(2501016)

O-Ring
(2501014)

1. Remove power from the instrument and turn off all flows.

2. Remove the cover by loosening the four screws securing the

cover (they do not have to be removed) and pulling the cover
upward while pushing down on the top of the front panel of the
instrument or on the viewing window mount.

3. Remove the screw that holds the inlet fitting in place.

4. Pull the inlet fitting out of the Electrospray chamber. Use a

twisting motion if necessary.

Maintenance 5–3

5. Detach the capillary from the inlet fitting (see “Removing the

Capillary” later in this chapter).

6. Remove the O-rings using a tweezers or similar tool. Inspect the

O-rings for damage and replace if necessary.

7. Use a soft cloth soaked in alcohol or a mild solvent to clean the

outside of the inlet fitting and flush the inside of the inlet fitting
with alcohol or a mild solvent to clear any deposits that may
have formed.

8. Rinse the inlet fitting with clean water.

9. Blow clean, dry air through and on the inlet fitting to evaporate

the water.

10. Replace the O-rings and lightly apply the vacuum grease

supplied with the instrument. Remove any excess grease.

11. Replace the inlet fitting and reinstall the capillary (see

“

Installing the Capillary” later in this chapter).

12. Replace the cover on the instrument and tighten the four

screws that secure the cover.

Cleaning the Aerosol Exit Port

The aerosol exit port can be cleaned as needed without
disassembling the instrument. Simply remove power and turn off
all flows to the instrument and use a cotton swab moistened with
alcohol or a mild detergent to clean the inside of the aerosol exit
port (see Figure 3-2).

Cleaning the Viewing Window Lens

If the viewing window lens becomes dirty, it can be cleaned without
removing the cover from the instrument. First try cleaning the lens
without disassembling the instrument by using a cotton swab
soaked in alcohol, a mild detergent, or a lens cleaner. If the lens is
still dirty, use the following procedure to clean the viewing window
lens:

1. Remove power from the instrument and turn off all flows.

2. Using Figure 5-2 as a guide, unscrew the viewing window

mount by hand and remove the lens ring retainer using a coin.

3. Turn the viewing window mount upside down to remove the

lens.

4. Clean the lens using a soft cloth soaked in alcohol, a mild

detergent, or a lens cleaner.

5. If necessary, the O-rings can be removed from the viewing

window mount and the viewing window mount can be cleaned
using a soft cloth soaked in alcohol or a mild detergent.

5–4 Model 3480 Electrospray Aerosol Generator

6. Replace the lens in the viewing window mount, making sure the

Lens Ring Retainer

Lens

O-Ring (2501010)

Viewing Window Mount

O-Ring (2501862)

O-rings are installed properly. The flat side of the lens should
be facing the O-ring.

Figure 5-2

Viewing Window Assembly

7. Secure the lens by tightening the lens ring retainer using a coin.

Do not overtighten as it could damage the lens.

8. Lightly grease the external O-ring and wipe off any excess

grease before replacing the viewing window mount in the
Electrospray chamber.

If the view of the capillary tip is still unsatisfactory after focusing
the lens, see the section later in this chapter, “

Cleaning the

Electrospray Chamber.”

Replacing the Ionizer

WARNING

The use of controls, adjustments, or procedures other than those
specified in this manual may result in exposure to hazardous radiation.

The ionizer does not need to be removed or cleaned under normal
operating conditions. However, the ionizer should be removed if the
Electrospray chamber needs to be cleaned or if the ionizer is more
than twelve months old. Use the following procedure to replace the
ionizer. Refer to Figure 2-2 if necessary.

Maintenance 5–5

1. Remove the ionizer retainer using the ionizer retainer tool

supplied in the accessory kit.
returning the ionizer.

2. Place the new ionizer in the ionizer retainer. The ionizer mesh-

side should be facing the open end of the ionizer retainer.

3. Install the ionizer retainer, making sure the O-ring is between

the ionization chamber and the ionizer retainer, and tighten
with the ionizer retainer tool.

Contact TSI for instructions on

Cleaning the Electrospray Chamber

WARNING

High voltage is accessible in several locations within this instrument.
Make sure you unplug the power source before removing the cover or
performing maintenance procedures.

The Electrospray chamber should not need cleaning as often as the
orifice plate under most operating conditions. However, the
Electrospray chamber should be checked periodically for corrosion
or aerosol deposits depending on the nature of the chemicals used
in the Electrospray. It is easiest to clean the Electrospray chamber
while cleaning the orifice plate. Refer to Figure 5-3 and use the
following procedure to clean the Electrospray chamber:

1. Follow steps 1 through 10 in the section “

Plate” earlier in this chapter. In addition, you may want to

remove the capillary to avoid damage while cleaning the
Electrospray chamber. See the section “
later in this chapter for details.

2. Remove the ionizer using the ionizer retainer tool supplied in

the accessory kit and place the ionizer in a safe place. Use
Figure 2-2 as a guide if necessary.

Cleaning the Orifice

Removing the Capillary”

5–6 Model 3480 Electrospray Aerosol Generator

Aerosol
Exit Tube

Common Ground Screw

Exit Manifold Block

O-Ring (2501029)

Ionization Chamber

Inlet Manifold Block

Viewing Window
Lens Assembly

Hex Nut

Inlet Fitting

Hex Nut

Figure 5-3

Cleaning the Electrospray Chamber

Capillary Inserts
Here

3. Remove the common ground screw on the side of the

Electrospray chamber. Also detach the viewing window LED
connector from the main PCB.

4. Detach the Electrospray chamber from the cabinet by removing

the two screws on the back panel of the instrument behind the
Electrospray chamber (not shown in Figure 5-3).

5. Remove the eight screws that fasten the two white manifold

blocks to the inlet and exit of the ionization chamber. The
viewing window lens can be cleaned if necessary by following
the instructions in the section “

Cleaning the Viewing Window
Lens” earlier in this chapter. The viewing window LED mount

can also be removed to clean the optical window it holds in
place by using the following procedure:

a) Unscrew the viewing window LED mount. The optical

window and an O-ring will fall out of the inlet manifold.

Maintenance 5–7

b) Clean the optical window using a soft cloth or cotton swab

moistened with alcohol, a mild detergent, or a lens cleaner.

Caution

Before replacing the viewing window LED mount, make sure the optical

!

window is flush with the O-ring. Failure to do so could result in breakage
of the optical window as the viewing window LED mount is screwed into
the inlet manifold.

c) Place the O-ring and optical window in the inlet manifold,

making sure the optical window is flush with the O-ring
surface, then replace the viewing window LED mount.

6. Use a soft cloth or cotton swab moistened with alcohol or a mild

detergent to clean the inside of the aerosol exit tube and the
stainless steel surface of the aerosol exit tube that faces the
inside of the Electrospray chamber.

7. Clean the inside of the ionization chamber using a soft cloth or

cotton swab moistened with alcohol or a mild detergent.

8. Reassemble the inlet and exit manifolds to the ionization

chamber and connect the Electrospray chamber to the cabinet.

9. Reattach the viewing window LED connector to the main PCB

and reconnect the three ground wires to the ionization
chamber.

10. Place the ionizer in the ionizer retainer. The ionizer mesh-side

should be facing the open end of the ionizer retainer.

11. Install the ionizer retainer, making sure the O-ring is between

the ionization chamber and the ionizer retainer, and tighten
with the ionizer retainer tool.

12. Replace the inlet fitting. If needed, refer to step 11 in the section

“

Cleaning the Orifice Plate” earlier in this chapter.

13. Install the capillary tube using the instructions later in this

chapter titled “

14. Perform and air leak test using the instructions below.

Installing the Capillary.”

Performing an Air Leak Test

Whenever an air leak is suspected or a significant part of the
Electrospray chamber has been reassembled, perform a leak test to
assure proper operation. Use these steps to check the entire
instrument for leaks. Skip to the next section if you want to isolate
the Electrospray chamber and check it for leaks.

5–8 Model 3480 Electrospray Aerosol Generator

WARNING

High voltage is accessible in several locations within this instrument.
Make sure you unplug the power source before removing the cover or
performing maintenance procedures.

Leak Checking the Entire Electrospray Instrument

1. Remove power from the instrument and turn off all flows.

2. Remove the cover by loosening the four screws securing the

cover (they do not have to be removed) and pulling the cover
upward while pushing down on the top of the front panel of the
instrument or on the viewing window mount.

3. Make sure a capillary is installed and all internal tubing is

connected properly (see the flow schematic in

Appendix B).

4. Turn off the external air and CO

external air and CO

connections and plug each port.

2

supplies or disconnect the

2

5. Plug the exhaust filter inside the instrument.

6. Connect a pressure gauge or manometer between the aerosol

exit port and a leak-tight valve. The valve should be closed.

7. Connect the valve to a vacuum source or a vacuum pump

capable of drawing 18 inHg vacuum.

8. Turn on the vacuum pump or vacuum system and slowly open

the valve. Allow the vacuum gauge reading to become stable
and then close the valve.

9. Observe the gauge reading. The reading should not change by

more the 0.5 inHg in 1 minute.

10. If the instrument does leak, follow the steps below under

“

Isolating Leaks,” or continue with the section, “Leak Checking

the Electrospray Chamber and Pressure Chamber.”

Leak Checking the Electrospray Chamber and Pressure Chamber

1. Remove power from the instrument.

2. Remove the cover by loosening the four screws securing the

cover (they do not have to be removed) and pulling the cover
upward while pushing down on the top of the front panel of the
instrument or on the viewing window mount.

3. Make sure a capillary is installed.

4. Disconnect the tubing from the barbed fitting on the pressure

chamber and the two barbed fittings on the Electrospray
chamber.

Maintenance 5–9

5. Plug all three barbed fittings.

6. Connect a pressure gauge or manometer between the aerosol

exit port and a leak-tight valve. The valve should be closed.

7. Connect the valve to a vacuum source or a vacuum pump

capable of drawing 18 inHg vacuum.

8. Turn on the vacuum pump or vacuum system and slowly open

the valve. Allow the vacuum gauge reading to become stable
and then close the valve.

9. Observe the gauge reading. The reading should not change by

more the 0.5 inHg in 1 minute.

10. If the instrument does leak, follow the steps below under

“

Isolating Leaks.”

Isolating Leaks

1. Isolate the leak by wetting suspected joints with clean isopropyl

alcohol while the system is under vacuum. The alcohol will be
drawn into a leaky joint and evaporate.

2. After isolating the leak, repair it (usually by greasing or

replacing an O-ring, or by sealing a fitting).

3. Blow clean, dry air through the repaired section to evaporate

and remove any leftover alcohol.

4. If you cannot find the leak, or cannot repair the leak, please

contact TSI for assistance.

Cleaning the Pressure Chamber

The pressure chamber can be cleaned if the surfaces appear dirty
or the sample vial is difficult to see clearly. Refer to Figure 5-4 and
use the following procedure to clean the pressure chamber:

WARNING

High voltage is accessible in several locations within this instrument.
Make sure you unplug the power source before removing the cover or
performing maintenance procedures.

1. Remove power from the instrument and turn off all flows.

2. Remove the capillary using the instructions in the next section

titled “

Removing the Capillary.”

3. Remove the screw attaching the high-voltage cable to the fitting

on top of the pressure chamber. The fitting can then be
removed by twisting counter-clockwise, using caution not to
bend or damage the platinum high-voltage wire.

5–10 Model 3480 Electrospray Aerosol Generator

Caution

When removing the fitting on top of the pressure chamber, use caution

!

not to bend or damage the platinum high-voltage wire.

4. Clean the top and bottom of the pressure chamber using a soft

cloth or cotton swab moistened with alcohol or a mild detergent.

High Voltage Cable

Hex Nut

High Voltage Fitting

Platinum High
Voltage Wire

Pressure Chamber
Top Half

Pressure Chamber
Bottom Half

Pin Groove (2X)

O-Ring (2501024)

Figure 5-4

Cleaning the Pressure Chamber

Maintenance 5–11

5. Generously grease the O-ring on the bottom half of the pressure

chamber and the pin grooves using the vacuum grease supplied
in the accessory kit. Remove excess grease and insert the
bottom half into the top half of the pressure chamber. Reapply
vacuum grease to the O-ring and pin grooves if necessary.

6. Reinstall the high-voltage fitting, using caution not to bend or

damage the platinum high-voltage wire.

7. Reattach the high-voltage cable to the inlet fitting and install

the capillary using the instructions in the next section titled
“

Installing the Capillary.”

Special Maintenance

Removing the Capillary

The capillary needs to be removed when cleaning any part of the
Electrospray chamber or if the capillary becomes damaged or the
capillary tip becomes dirty. Use the following steps and Figure 5-5
to remove the capillary:

WARNING

High voltage is accessible in several locations within this instrument.
Make sure you unplug the power source before removing the cover or
performing maintenance procedures.

1. Remove power from the instrument and turn off all flows.

2. Remove the cover by loosening the four screws securing the

cover (they do not have to be removed) and pulling the cover
upward while pushing down on the top of the front panel of the
instrument or on the viewing window mount.

5–12 Model 3480 Electrospray Aerosol Generator

High Voltage
Shield

High Voltage
Fitting

Inlet Fitting

Hex Nut

Capillary

Capillary Sleeve

Hex Nut

Figure 5-5

Removing or Installing the Capillary

3. Loosen the hex nut on the inlet fitting but do not remove it.

4. Carefully pull the capillary from the capillary guide leaving the

guide behind.

Caution

When removing the capillary from the inlet fitting, the capillary can

!

become damaged if not removed carefully. Read the note below for hints
on removing the capillary without damage.

Note: When removing the capillary slowly, the capillary tip will have

a tendency to hit the edge of the hex nut on the inlet fitting if it
is not pulled straight out from the inlet fitting. To prevent
damage to the capillary, use a steady hand and pull the
capillary straight out from the inlet fitting or pull the capillary
out slowly until it is almost removed and then pull quickly to
completely remove the capillary. One alternative solution is to
remove the inlet fitting before removing the capillary. Another
is to perform steps 5–7 before steps 3 and 4.

5. Remove the high-voltage shield by loosening the mounting

screw and pulling the high-voltage shield upward until it clears
the capillary.

6. Loosen the hex nut on the high-voltage fitting but do not

remove it.

Maintenance 5–13

7. Pull the capillary straight up until it clears the high-voltage

fitting.

8. Store the capillary in the case provided to prevent breakage.

Cleaning the Capillary Tip

If the capillary tip appears dirty, remove the capillary using the
instructions above, and rinse or soak the capillary tip in alcohol or
a mild detergent until the contaminants are removed. Then install
the capillary using the instructions in the next section.

Installing the Capillary

WARNING

High voltage is accessible in several locations within this instrument.
Make sure you unplug the power source before removing the cover or
performing maintenance procedures.

To install the capillary, refer back to Figure 5-5 and use the
following instructions:

1. Remove power from the instrument and turn off all flows.

2. Remove the cover by loosening the four screws securing the

cover (they do not have to be removed) and pulling the cover
upward while pushing down on the top of the front panel of the
instrument or on the viewing window mount.

3. Loosen the hex nut on the inlet fitting but do not remove it.

4. Remove the high-voltage shield by loosening the mounting

screw and pulling the high-voltage shield upward.

5. Loosen the hex nut on the high-voltage capillary guide but do

not remove it.

6. Insert the long end of the capillary into the high-voltage

capillary guide until the end of the capillary reaches the end of
the platinum wire. Twist the capillary until it becomes retained
by the corkscrew of the platinum wire, then tighten the hex nut
on the high-voltage fitting.

7. Attach the high-voltage shield to the cabinet by sliding the

capillary through the high-voltage shield, routing the high­voltage wire through the groove in the bottom edge of the high­voltage shield, and tightening the mounting screw.

8. Turn on the power to the instrument. If the cover is removed,

high voltage will not be supplied to the instrument, but the
capillary viewing window LED will turn on.

5–14 Model 3480 Electrospray Aerosol Generator

9. Carefully insert the capillary tip into the capillary guide. While

looking through the viewing window, continue pushing the
capillary into the capillary guide until the tip of the capillary
first appears, then tighten the hex nut on the inlet fitting.

10. If the capillary is centered in the viewing window, installation is

complete. If not, loosen the hex nut on the inlet fitting, adjust
the position of the capillary, and retighten the hex nut.

Note: Due to variations in the dimensions of the viewing window

components, the capillary may appear slightly off center in the
direction transverse to the capillary axis. This is not a cause
for concern however, because the center of the orifice plate is
aligned to the inlet fitting axis at the factory.

11. Replace and secure the cabinet cover. The Electrospray is now

ready for use (See Chapter 4, “

Operating the Electrospray”).

Adjusting the Position of the Capillary Tip

If the capillary does not appear in the center of the viewing window
or you wish to move the capillary closer or further from the orifice
plate, refer to the instruction preceding this subsection titled,
“

Installing the Capillary.” Step 10 lists instructions for adjusting

the position of the capillary tip. Make sure to remove power from
the instrument and turn off all flows before removing the cover from
the instrument.

Adjusting the Position of the Capillary and the Platinum Wire in the Pressure Chamber

In the pressure chamber, the capillary and the platinum wire are
positioned at the factory to extend near the bottom of a standard
sample vial (1.7mL centrifuge tube). In most cases, the sample to
be electrosprayed can be put into a standard sample vial; however,
if a smaller vial must be used, the following things must be done:

Caution

The electronic circuits within this instrument are susceptible to
electrostatic discharge (ESD) damage. Use ESD precautions to avoid
damage.

 Use only a table top with a grounded conducting surface.
 Wear a grounded, static-discharging wrist strap.

WARNING

High voltage is accessible in several locations within this instrument.
Make sure you unplug the power source before removing the cover or
performing maintenance procedures.

Maintenance 5–15

 Obtain a short piece of a non-conductive piece of hollow tubing

or a similar object to place in the bottom half of the pressure
chamber to allow the smaller vial to be placed securely.

 Cut the platinum high-voltage wire to length or replace the

platinum high-voltage wire with a new platinum wire of desired
shape and size. To modify or replace the platinum high-voltage
wire, use the instructions earlier in this chapter titled “

Cleaning
the Pressure Chamber” to remove the capillary and the high-

voltage fitting. The platinum high-voltage wire is soldered to the
inside of the brass pin on the bottom of the high-voltage fitting
and can be removed by heating with a soldering iron. Finally,
solder the new platinum wire to the inside of the brass pin and
replace the high-voltage fitting.

 Reinstall the capillary using the instructions earlier in this

chapter titled “

Installing the Capillary.”

Reversing the High-Voltage Polarity

Caution

The electronic circuits within this instrument are susceptible to
electrostatic discharge (ESD) damage. Use ESD precautions to avoid
damage.

 Use only a table top with a grounded conducting surface.
 Wear a grounded, static-discharging wrist strap.

WARNING

High voltage is accessible in several locations within this instrument.
Make sure you unplug the power source before removing the cover or
performing maintenance procedures.

Note: Refer to Figure 5-6 and note the location of the high-voltage

power supply to determine whether a high-voltage module has
a positive or negative polarity. In a positive module (shown),
the high-voltage power supply is located on the exposed side
of the high-voltage PCB. In a negative module, the high-voltage
power supply is located on the opposite side of the high­voltage PCB.

5–16 Model 3480 Electrospray Aerosol Generator

High Voltage
Module

High Voltage
PCB

High Voltage
Power Supply

Figure 5-6

Determination of High-Voltage Polarity

The standard Electrospray is equipped with a positive high-voltage
module, which causes the generated droplets to initially have a
high-positive charge. However, if initially negatively charged
droplets are desired, a negative high-voltage module is available
from TSI. Reversing the high-voltage polarity is a procedure that
should only be performed by a qualified electronics technician
observing ESD precautions. To replace one high-voltage module
with another, refer to Figure 5-7 and proceed as follows:

1. Remove power from the instrument and turn off all flows.

2. Remove the cover by loosening the four screws securing the

cover (they do not have to be removed) and pulling the cover
upward while pushing down on the top of the front panel of the
instrument or on the viewing window mount.

Maintenance 5–17

Main PCB

High Voltage
Module

Captive Screw (2X)

High Voltage
Cable Connector

Figure 5-7

Reversing the High-Voltage Polarity

3. Disconnect the high-voltage cable from the high-voltage module

by gripping the connector and twisting the collar

1

⁄8-turn

clockwise. The connector should then separate easily from the
socket.

4. Loosen the two captive screws attached to the high-voltage

module until the screws pop out.

5. Pull the high-voltage module straight out until it clears the

spacers used to secure the main PCB.

6. Install the high-voltage module with the desired polarity in the

same orientation as the high-voltage module that was removed,
making sure the six connector pins on the main PCB are
aligned with the six sockets on the high-voltage PCB. Tighten
the two captive screws finger tight.

7. Reconnect the high-voltage cable by pushing the connector into

the socket. There is a

1

⁄8-turn spring locking connect that

secures the connector when it is seated properly.

8. Replace the cover on the instrument and tighten the four

screws that secure the cover.

5–18 Model 3480 Electrospray Aerosol Generator

Cleaning the Pressure Regulator

The air supplied to the pressure regulator should always be from a
clean, dry air supply, eliminating the need to clean the pressure
regulator. However, if you suspect the regulator has become dirty,
refer to

Appendix A for the manufacturer’s specifications and

instructions for maintaining the pressure regulator.

Cleaning the Rotameters

The air supplied to the air rotameter should always be from a clean,
dry air supply, eliminating the need to clean the air rotameter.
However, if you suspect the air rotameter has become dirty, refer to

Appendix A for the manufacturer’s specifications and instructions

for maintaining the air rotameter.

The CO
compressed gas cylinder containing dry CO

supplied to the CO2 rotameter should be supplied from a

2

gas. After the CO2

2

enters the Electrospray instrument from the back panel, it flows
through a filter before entering the CO
CO

rotameter should not need to be cleaned under normal

2

operating conditions. However, if you suspect the CO
has become dirty, refer to

Appendix A for the manufacturer’s

specifications and instructions for maintaining the CO

rotameter; therefore, the

2

rotameter

2

rotameter.

2

Replacing the Filters

Because the level of contaminants entering the Electrospray in the
air and CO
need to be replaced under normal operating conditions.

Replacement Parts

This subsection contains information on replacement parts
available from TSI and their part numbers. See also the section in

Chapter 2 for information on parts included in the accessory kit,

which are also available as replacement parts.

Table 5-2

Replacement Parts

Part Description Part Number

Shield, High-Voltage Fitting 2904157

Wire, High-Voltage Platinum 3301754

Assembly, Viewing Window LED 1035928

Optical Window, Viewing Window LED 2502623

Lens, Viewing Window 2502622

Filter, Balston BQ In-Line (4 in unit) 1602060

is low, the four internal filters in the Model 3480 do not

2

Maintenance 5–19

Part Description Part Number

Tubing, Silicone

1

⁄8” Barb

High-Voltage Module

3001257

1035907
(please specify positive or negative)

Capillaries 25 µm (25 per pack) 3900124

Capillaries 30 µm (25 per pack) 3900125

Capillaries 40 µm (25 per pack) 3900126

Capillary Sleeve Guide 1705014

Neutralizer 348002

Filter, Balston BX on T-Connector 1602230

5–20 Model 3480 Electrospray Aerosol Generator

CHAPTER 6

Troubleshooting

This chapter lists potential problems and their solutions.

Electrospray Operation is Unstable

If the Electrospray is not operating in the Cone-Jet mode (see
Chapter 4, “
not stable, first try decreasing the voltage setting to its minimum
value and then increase the voltage setting until the Cone-Jet mode
appears in the viewing window. If the Cone-Jet mode appears, the
current display should be stable. If this procedure does not resolve
your problem, use Table 6-1 to pinpoint possible solutions.

Operating the Electrospray”) or the current display is

6-1

Table 6-1

Troubleshooting if the Electrospray Operation is Unstable

Problem Solutions

Electrospray is operating in
the Dripping mode (see
Chapter 4, “Operating the
Electrospray”)

or

Current display is much
lower and more unstable
than normal

Electrospray is operating in
the Pulsating mode (see
Chapter 4, “Operating the
Electrospray”)

or

Current display is lower and
more unstable than normal

Electrospray is operating in
the Corona Discharge mode
(see Chapter 4, “Operating
the Electrospray”)

or

Current display is higher and
more unstable than normal

No liquid is flowing through
the capillary

There is no current reading Make sure the voltage, pressure, and flow rates are adjusted properly

Increase the voltage setting
Increase the capillary pressure drop
Increase the air flow rate
Purge the capillary (see
Clean the capillary tip (see
Adjust the position of the capillary (see Chapter 5, “
Clean the inlet fitting (see
Increase the conductivity of the sample (see

Chapter 5)

Chapter 5)

Installing the Capillary”)

Chapter 5)

Chapter 4)

Increase the voltage setting
Increase the capillary pressure drop
Purge the capillary (see
Clean the capillary tip (
Adjust the position of the capillary (see Chapter 5, “
Clean the inlet fitting (see
Increase the conductivity of the sample (see

Chapter 5)

Chapter 5)

Installing the Capillary”)

Chapter 5)

Chapter 4)

Decrease the voltage setting
Decrease the capillary pressure drop
Increase the CO
Purge the capillary (see
Clean the capillary tip (see
Adjust the position of the capillary (see Chapter 5, “
Clean the inlet fitting (see
Decrease the conductivity of the sample (see

flow rate

2

Chapter 5)

Chapter 5)

Installing the Capillary”)

Chapter 5)

Chapter 4)

Make sure the voltage, pressure, and flow rates are adjusted properly
Make sure the capillary is immersed in the sample vial solution
See the section below, “

Unplugging the Capillary”

Make sure the capillary is immersed in the sample vial solution
Make sure the platinum wire is immersed in the sample vial solution

6-2 Model 3480 Electrospray Aerosol Generator

Unplugging the Capillary

Each capillary is checked before leaving the factory to ensure
proper operation. However, a capillary can become fully or partially
plugged due to several reasons, including those listed in Table 6-2.

As a general rule, if the capillary becomes plugged and the capillary
tip is not broken, first try applying back pressure to the capillary
(see the procedure listed below), then try applying a 5 psi forward
pressure drop across the capillary, and finally try cleaning the
capillary tip or purging the capillary (see
is still plugged, it should be discarded and replaced (see

Table 6-2

Troubleshooting if the Capillary has Become Plugged

Reason Solution

A contaminant or large
particle in the sample vial
has plugged the capillary
inlet

Residue has built up on the
inner walls of the capillary

Residue has built up on the
capillary tip

The capillary has not been
cleaned properly when
shutting down the
Electrospray

The capillary tip has become
broken during maintenance
or handling procedures

Applying Back Pressure to the Capillary

Chapter 5). If the capillary

Chapter 5).

Back pressure the capillary using the
procedure listed below

Purge the capillary (see

Clean the capillary tip (see

Purge the capillary (see

Replace the capillary (see Chapter 5,
“

Removing the Capillary” and

“Installing the Capillary”)

Chapter 5)

Chapter 5)

Chapter 5)

If the capillary becomes plugged, the first attempt to unplug the
capillary should be to apply back pressure to the capillary. The
following procedure should unplug the capillary if a contaminant or
large particle in the sample vial has plugged the capillary inlet:

1. Remove power from the instrument and turn off all flows.

2. Connect a compressed air source capable of generating 5 psi

pressure or a large syringe (>50 cc) to the aerosol exit. Do not
exceed 5 psi since a relief valve is attached to the Electrospray
chamber. If the relief valve opens, remove all pressure from the
Electrospray chamber and the relief valve will reset
automatically.

Troubleshooting 6-3

!

Caution

Applying more than 5 psi pressure to the Electrospray chamber will cause
a relief valve to open. If the relief valve opens, remove all pressure from
the Electrospray chamber and the relief valve will reset automatically.

3. With a sample solution installed in the bottom half of the

pressure chamber, apply up to 5 psi pressure to the aerosol exit
for 15 seconds.

4. Remove pressure from the aerosol exit and run the Electrospray

under normal operating conditions to check if the capillary is
unplugged. If not, repeat steps 1–4 except apply back pressure
for several minutes until bubbles can be seen exiting the
capillary into the sample vial. If bubbles are not seen after
5 minutes at 5 psi back pressure, refer to the alternative
solutions mentioned earlier in this chapter to unplug the
capillary.

6-4 Model 3480 Electrospray Aerosol Generator

CHAPTER 7

Contacting Customer
Service

This chapter gives directions for contacting people at TSI
Incorporated for technical information and directions for returning
the Model 3480 Electrospray for service.

Technical Contacts

 If you have any difficulty setting up or operating the

Electrospray, or if you have technical or application questions
about this system, contact an applications engineer at TSI
Incorporated, 1-800-874-2811 (USA) or [phone].

 If the Electrospray does not operate properly, or if you are

returning the instrument for service, contact TSI at 1-800-874­2811 (USA) or [phone].

Returning the Electrospray for Service

Call TSI at 1-800-874-2811 (USA) or [phone] for specific
return instructions. Customer Service will need this information
when you call:

 The instrument model number

 The instrument serial number

 A purchase order number (unless under warranty)

 A billing address

 A shipping address

Prior to shipping any components to TSI for service or repair, please
utilize our convenient Return Material Authorization (RMA) Form,
which is available online at

www.tsi.com.

7-1

WARNING

The Model P-2042 Ionizer must be removed from the Electrospray prior to
shipping the instrument. See the section titled “
Chapter 5 for instructions on how to remove the ionizer. Do not ship the
ionizer to TSI if the instrument must be returned, rather keep the ionizer
and ship the instrument without the ionizer.

Note: The ionizer must be replaced 12 months from the date on the

ionizer label.
before the ionizer expiration date. When returning an ionizer,
contact TSI for handling and shipping instructions.

Contact TSI to order a new ionizer four weeks

Replacing the Ionizer” in

7-2 Model 3480 Electrospray Aerosol Generator

APPENDIX A

Model 3480
Specifications

The following specifications—which are subject to change—list the
most important features of the Model 3480 Electrospray Aerosol
Generator.

Table A-1

Specifications of the Model 3480 Electrospray Aerosol Generator

Mode of operation................

Capillary dimension.............

Particle type ........................

Initial droplet diameter .......

Particle generation rate.......

Particle size range ...............

Liquid conductivity .............

Liquid flow rate....................

Differential pressure ...........

Flow rates

Air ..................................

CO

2....................................................................

Aerosol ...........................

Ionizer* ................................

Front panel displays ............

Ports

Air inlet..........................

CO2 inlet.........................

Aerosol outlet ................

Voltage range .......................

Current range.......................

Dimensions (LWH)................

Weight ..................................

Power requirements.............

Fuse (not replaceable by user) ...

Generation of aerosols from liquid solutions or suspensions using an
electrospray method.

25 µm, 250 mm length

Solids or nonvolatile liquids soluble in 20 mM ammonium acetate
solution in ultrapure water or 0.05% trifluoroacetic acid in ultrapure
water. Suspensions in some solvents up to a particle size of 100 nm.

150 nm nominal

7

particles/cm3

>10

2 to 100 nm

0.2 S/m nominal

66 nL/min nominal

0 to 5 psi (3.7 psi nominal)

0.2 to 2.5 L/min (1 L/min nominal)

0.05 to 0.5 L/min (0.1 L/min nominal)

0.25 to 3 L/min, determined by the sum of air and CO

Bipolar, Po-210, 5 millicurie, half-life of 138 days, shipped
separately

LED, 3.5 digit voltage and current displays

¼ in. OD Swagelok connection

¼ in. OD Swagelok connection

¼ in. OD Stainless Steel tube

+0.5 to +3.5 kV (2.0 to 2.5 kV nominal, negative high-voltage module
available)

0 to 2000 nA (280 to 320 nA nominal)

20.3 cm × 40.4 cm × 25.7 cm (8.0 in. × 15.9 in. × 10.1 in.)

6.8 kg (15 lb)

85 to 260 VAC, 50/60 Hz, 25 W maximum

2.5A, 250 V, type 5x20 mm (not replaceable by operator)

flow rates

2

A-1

Environmental Conditions...

*TSI Incorporated is authorized by the United States Nuclear Regulatory Commission to distribute

these Ionizers. If your location is within the United States, no other federal license is required. Check
local regulations for your own protection. Ionizers are shipped separately. End-user name and
address is required. Contact TSI to return used ionizers or obtain replacements.

Specifications are subject to change without notice. TSI and the TSI logo are registered trademarks of
TSI Incorporated.

Indoor use
Altitude up to 2000 m (6500 ft)
Ambient temperature 10-50 °C
Ambient humidity 0-90% RH non-condensing
Over-voltage category II
Pollution degree II

Pressure Regulator Maintenance

The air supplied to the pressure regulator should always be from a
clean, dry air supply, eliminating the need to clean the pressure
regulator. However, if you suspect the regulator has become dirty,
use Figure A-1 and the instructions provided by the manufacturer
below to disassemble and clean the regulator.

Caution

Remove air supply pressure and bleed off output pressure prior to

!

performing maintenance.

To disassemble the pressure regulator, loosen
adjusting handwheel (1) until spring tension is
relieved. Remove six screws (9) and lift off bonnet
(5), spring plate (6), spring (7) and diaphragm
assembly (8). To remove nozzle assembly (10),

5

use

⁄8” socket wrench to remove nozzle assembly

to avoid damage to the nozzle. All parts may be
cleaned by immersion in a suitable solvent and
blowing dry with air stream.

To reassemble, replace nozzle assembly (10) and
place diaphragm assembly (8) over body (11),
with diaphragm plate up. Place spring (7) and
spring plate (6) on diaphragm assembly (8), re­install bonnet (5) and tighten six screws (9). The
six screws should be tightened alternately.

Figure A-1
Pressure Regulator Assembly

A-2 Model 3480 Electrospray Aerosol Generator

!

RETAINING CLIP

Rotameter Maintenance

If you suspect either rotameter has become dirty, refer to
Figure A-2 and the instructions provided by the manufacturer
below to clean either rotameter.

Caution

Remove air supply pressure and bleed off output pressure prior to
performing maintenance.

Occasional cleaning may become necessary if
dirt appears in the flowmeter or if float
movement is restricted. To clean, rotate
“Retaining Clip” (Located in the back of
flowmeter) counter-clockwise to align clip with
slot and then pull out. Then remove top plug,
ring (if required), outlet fitting and float only.
Tube does not need to be removed. Wash tapered
hole, float, outlet fitting and top plug with clean
water and a soft brush. Rinse all parts with clean
water and dry thoroughly. Avoid use of solvents
and strong bases for cleaning. Reassemble by
reversing above.

Figure A-2

Rotameter Back View

Model 3480 Specifications A-3

APPENDIX B

Theory of Operation

This appendix describes theories of operation for the Electrospray
Aerosol Generator.

System Description

The Electrospray consists of three main subsystems that are used
to generate a monodisperse aerosol.

 Pressure chamber—capillary—Electrospray chamber

 Air and CO

 High-voltage control

The pressure chamber—capillary—Electrospray chamber schematic
is shown in Figure B-1. A description of how the Electrospray
generates aerosol follows.

A sample solution is stored in a cone-shaped vial, enclosed in a
cylindrical pressure chamber. The chamber accommodates a
capillary and a platinum high-voltage wire, both of which are
immersed in the solution. Maintaining a differential pressure
causes the solution to be pushed through the capillary.

The high-voltage control regulates an electrical field exerted at the
capillary exit, which pulls the charged solution out of the capillary,
forming droplets that are mixed with clean air and CO
produces a sheath flow, which transports the droplets to the
Electrospray chamber. The highly charged droplets are neutralized
by a Polonium-210 source, and the liquid is evaporated before the
aerosol exits the instrument.

The remainder of this section discusses liquid flow in the capillary,
the Electrospray chamber design, aerosol neutralization, the flow
control system, and the high-voltage control and current
measurement methods used in the Electrospray.

flow control

2

. This

2

B–1

Figure B-1
Schematic Diagram of the Electrospray

Capillary Flow Characteristics

The liquid flow rate Q (nL/min) through the capillary is governed by
the following equation for Poiseuille flow in a circular tube:

4

⎛

⎞

1

Δ

PD

π

⋅⋅=

cQ

⎜
⎝

⋅

⎜

⎟

⎜

μ

2

8

⋅

⎠

⎝

⎞

⎛

c

where:

D

is the capillary inner diameter (µm)

c

µ is the liquid viscosity (poise)

ΔP is the pressure across the capillary (psi)

L is the length of the capillary (cm)
c is a constant to account for all unit conversions (4.14E4)

The capillary in the Electrospray has a diameter of 25 ±2 µm and a
length of 25 cm, a typical pressure across the capillary is 3.7 psi
(¼ atm), and the viscosity of water at 20°C is 0.89E-2 poise. Given
these conditions, the nominal liquid flow rate is 66 nL/min.
Table B-1 lists values of the liquid flow rate as a function of

⎞

⎛

⋅⎟⎟

⎠

Equation B-1

⎟

⎜

L

⎠

⎝

B–2 Model 3480 Electrospray Aerosol Generator

pressure and capillary diameter. Also included in the table is the
volume of the capillary, residence time of the liquid in the capillary,
and the length of time for 1 mL to flow through the capillary.

Table B-1

Capillary Flow Characteristics for Water at 20°C

Capillary

Pressure Drop

ΔP (psi)

2.00 25 35.7 122.7 206 19.5

2.20 25 39.2 122.7 188 17.7

2.40 25 42.8 122.7 172 16.2

2.60 25 46.4 122.7 159 15.0

2.80 25 49.9 122.7 147 13.9

3.00 25 53.5 122.7 138 13.0

3.20 25 57.1 122.7 129 12.2

3.40 25 60.7 122.7 121 11.4

3.60 25 64.2 122.7 115 10.8

3.70 25 66.0 122.7 112 10.5

3.80 25 67.8 122.7 109 10.2

4.00 25 71.4 122.7 103 9.7

4.20 25 74.9 122.7 98 9.3

4.40 25 78.5 122.7 94 8.8

4.60 25 82.1 122.7 90 8.5

4.80 25 85.6 122.7 86 8.1

5.00 25 89.2 122.7 83 7.8

2.00 23 25.6 103.9 244 27.2

2.00 25 35.7 122.7 206 19.5

2.00 27 48.5 143.1 177 14.3

3.00 23 38.3 103.9 163 18.1

3.00 25 53.5 122.7 138 13.0

3.00 27 72.8 143.1 118 9.5

3.70 23 47.3 103.9 132 14.7

3.70 25 66.0 122.7 112 10.5

3.70 27 89.8 143.1 96 7.7

4.00 23 51.1 103.9 122 13.6

4.00 25 71.4 122.7 103 9.7

4.00 27 97.1 143.1 88 7.2

5.00 23 63.9 103.9 98 10.9

5.00 25 89.9 122.7 83 7.8

5.00 27 121.3 143.1 71 5.7

Capillary Inner

Diameter

Dc (µm)

Liquid Flow

rate

Q (nL/min)

Capillary

Volume

V (nL)

Liquid

Residence

Time

tr (sec)

Sample Time

ts (days/mL)

Theory of Operation B–3

Calculating Primary Droplet Diameter

As the liquid reaches the end of the capillary, the electric field
induces a surface charge on the liquid. The electrostatic charge of
the liquid produces forces that cause the liquid to disperse into a
fine spray of charged droplets. The diameter of the charged droplet
as it first leaves the tip of the capillary is referred to as the primary
droplet diameter. After the primary droplet is generated, the liquid
from the primary droplet evaporates in the ionization chamber and
an aerosol particle remains. If a sucrose solution is used to
generate an aerosol, the sucrose concentration can be varied to
generate different particle diameters. For any sucrose particle
diameter D
the sucrose concentration C (expressed as a decimal) is known by
using the following expression:

D ⋅=

Empirical formulas expressing the particle diameter (from which
the primary droplet diameter can be calculated) of a 0.1% V/V
sucrose solution as a function of (Q/K)
rate and K is the electrical conductivity of the liquid, have been
reported in publications such as:

Chen, Da-Ren, David Y.H. Pui, and Stanley L. Kaufman [1995]
“Electrospraying of Conducting Liquids for Monodisperse Aerosol
Generation in the 4 nm to 1.8 µm Diameter Range.”
J. Aerosol Sci., 26:963-977.

, the primary droplet diameter Dd can be calculated if

p

1

C

Equation B-2

D

pd

3/1

1/3

, where Q is the liquid flow

Electrospray Chamber

Immediately after the highly charged primary droplets are
generated at the capillary tip, they are transported by an air/ CO
sheath flow mixture through an orifice plate to the ionization
chamber. This must be done quickly because after the primary
droplet is generated, the liquid begins to evaporate, which
decreases the surface area of the droplet, thereby increasing the
surface charge density. If the surface charge density becomes too
large, the Coulombic repulsive forces on the droplet will cause
Rayleigh disintegration, resulting in a less monodisperse aerosol.

To reduce the charge on each primary droplet, the Electrospray
chamber houses a Polonium-210 radioactive alpha-emitter ionizer.
The nature of the flow through the orifice plate into the ionization
chamber and the placement of the ionizer cause the droplets to
encounter the ions nearly immediately upon their formation.

B–4 Model 3480 Electrospray Aerosol Generator

2

Equilibrium Charging Theory

The equilibrium charge distribution generated by the ionizer of the
Electrospray can be represented by a theoretical model developed
by Wiedensohler [1986], which is an approximation of the Fuchs
[1963] diffusion theory for particle sizes in the submicrometer
regime.

Figure B-2 shows the measured data of Wiedensohler [1986] and
theoretical curves based on the theory of Fuchs [1963] and
calculated by Wiedensohler [1988]. The theoretically determined
charge distribution agrees well with experimental data. It can be
seen from the figure that the fraction of positively charged particles
is different from the fraction of negatively charged particles.
Table B-2 lists the fractions of particles in air that carry +1, +2, +3,
and +4 charge units.

Figure B-2
Bipolar Particle Charge Distribution in Air [Wiedensohler and Fissan, 1988]

Theory of Operation B–5

Table B-2

Midpoint Particle Diameters and Fraction of Total Particle Concentration
that Carries +1, +2, +3, and +4 Elementary Charges

Fraction of Total Particle
Particle Concentration That Carries This
Diameter Number (1-4) of Positive Charges
Midpoint, nm +1 +2 +3 +4

10 0.0411 0 0 0
11 0.0460 0 0 0
12 0.0514 0 0 0
14 0.0573 0 0 0
15 0.0638 0 0 0
17 0.0709 0 0 0
18 0.0784 0 0 0
21 0.0866 0.00012 0 0
23 0.0953 0.00023 0 0
25 0.1041 0.00041 0 0
28 0.1145 0.0007 0 0
31 0.1241 0.0011 0 0
35 0.1343 0.0018 0 0
38 0.1446 0.0027 0 0
43 0.1550 0.0040 0 0
48 0.1650 0.0056 0 0
53 0.1748 0.0078 0 0
59 0.1841 0.0105 0 0
66 0.1925 0.0138 0 0
74 0.2000 0.0180 0.00045 0
83 0.2064 0.0225 0.00089 0
93 0.2113 0.0279 0.0016 0
104 0.2148 0.0339 0.0028 0
117 0.2167 0.0406 0.0046 0.00014
132 0.2167 0.0477 0.0072 0.00031
150 0.2149 0.0552 0.0105 0.00064
170 0.2113 0.0627 0.0149 0.0012

The formulas used to calculate Table B-2 are shown below. They
are taken from Wiedensohler [1988]. To calculate the fraction of
particles carrying zero, one or two charges, use Equation B-4 which
is an approximation of the Fuchs model. Equation B-4 is valid for
size ranges: 1 nm ≤ D
≤ 1000 nm for N = -2, 2; and for D

≤1000 nm for N = -1, 0, 1; for 20 nm ≤ Dp

p

≤ 20 nm for N ≤ 1.

p

i

⎡

5

∑

⎢

=

i

Nf

⎣

=

10)(

0

a

i

N

()

D

⎛

log

⎜

nm

⎝

⎤

p

⎞
⎟

⎥

⎠

⎦

B–6 Model 3480 Electrospray Aerosol Generator

Equation B-4

Table B-3
Coefficients for Equation B-4

ai(N) N=-2 N=-1 N=0 N=1 N=2

ao -26.3328 -2.3197 -0.0003 -2.3484 -44.4756
a1 35.9044 0.6175 -0.1014 0.6044 79.3772
a2 -21.4608 0.6201 0.3073 0.4800 -62.8900
a3 7.0867 -0.1105 0.3372 0.0013 26.4492
a4 -1.3088 -0.1260 0.1023 -0.1553 -5.7480
a5 0.1051 0.0297 -0.0105 0.0320 0.5049

For the fraction of particles carrying three or more charges, use
Equation B-5 which is based on an derivation by Gunn from 1956.

2

πε

⎡

−−

N

⎢

=

)(

Nf

e

2

4

kTD

επ

p

0

exp

⎢

⎣

2

kTD

⎛

p

0

2

e

2

πε

0

e

Z

⎜

ln

⎜

Z

⎝

kTD

p

2

2

⎤

⎞

i

+

⎟

⎥

⎟

⎥

i

−

⎠

⎦

Equation B-5

where:

e = elementary charge
= 1.60217733E-19 coulomb

ε

= dielectric constant

0

= 8.854187817E-12 farad/m (for air)
D

= particle diameter [m]

p

k = Boltzmann’s constant
= 1.380658E-23 joule/K (for air)
T = Temperature [K]
N = number of elementary charge units
Z

= ion mobility ratio

i+/Zi-

= 0.875 (Wiedensohler)

Air and CO2 Flow Control

This section describes the flow of air and CO2 through the
Electrospray. A flow schematic is shown in Figure B-3.

Theory of Operation B–7

AIR
IN

CO
IN

ORIFICE

DIFFERENTIAL
PRESSURE
REGULATOR

FILTER

(ACROSS CAPILLARY TUBE)

P

ROTAMETER

FILTER

FILTER

2

ROTAMETER

FILTER

EXHAUST

ORIFICE

TO
PRESSURE
CHAMBER

TO
IONIZATION
CHAMBER

Figure B-3
Electrospray Flow Schematic

The differential pressure regulator is used to maintain the pressure
drop across the Electrospray capillary; therefore, if the flow rates of
the air and CO

into the Electrospray chamber are changed, the

2

capillary pressure drop will not change. The high pressure tap for
the pressure gauge is connected to the output of the pressure
regulator, which is at the same pressure as the pressure chamber.
The low pressure tap is connected in the same orientation as the
air/CO

mixture inlet to the ionization chamber, which is

2

immediately upstream of the capillary tip.

The orifice leading to the pressure chamber is used to allow the
quick-release pressure chamber bottom to be removed without
changing the position of the differential pressure regulator knob.

The exhaust orifice is used to provide “bleed” and “relief” features to
the differential pressure regulator. This increases the regulator
stability and responsiveness by keeping the regulator in a dynamic
state. It also provides a quicker exhaust when the regulator output
pressure exceeds the set point pressure.

The air and CO

rotameters provide separate controls for each flow

2

before the flows are mixed together immediately upon exit of the
rotameter. The filter provides a final clean of the sheath flow as well
as a means to mix the air and CO

thoroughly before the entrance

2

to the ionization chamber.

B–8 Model 3480 Electrospray Aerosol Generator

Voltage and Current Measurement

The voltage and current of the Electrospray circuit are displayed on
the digital front-panel meters. This section describes how the
voltage and current displays are measured.

Voltage Measurement

The voltage at the output of the high-voltage supply is divided down
through series resistors. Two 10 MΩ resistors are used to reduce
the maximum current of the high-voltage supply. If a person comes
into contact with the high-voltage fitting of the Electrospray the
maximum current is 0.25 mA. A further divider of two 50 MΩ and
one 100 kΩ resistor divides the voltage of the Electrospray down by
a factor of 1000. The sense voltage is picked up at the 100 kΩ
resistor and buffered through an OP-27 follower. Two IN-457, low
leakage diodes are used as clamping diodes across the op-amp
inputs. In order to reduce the voltage for the ±2 V voltmeter display,
the voltage is further divided down by a factor of 10. This also
provides the opportunity to balance any divider tolerance on the
high-voltage divider. A capacitor of 0.1 µF on the input of a second
op-amp follower with the resistors provides a filter for any noise.

Current Measurement

To measure the current of the Electrospray, an op-amp operation
as a current-to-voltage converter is used. The current path
measured goes from the positive high-voltage supply side into the
current-to-voltage converter, and then into the analog ground.
From the analog ground, the current path continues through the
grounded electrospray side, through the Electrospray (in the form
of charged droplets), through the liquid in the capillary, through a
20 MΩ protection resistor, and into the negative high-voltage
supply side.

Selected References

The following list contains papers that are referenced in this
appendix as well as other references that may be interesting to the
reader.

Adachi, M., K. Okuyama and T. Kousaka [1985]
“Electrical Neutralization of Charged Aerosol Particles by Bipolar
Ions.” Journal of Chemical Engineering, Japan, 16:229.

Theory of Operation B–9

Bailey, Adrian G. [1988]
Electrostatic Spraying of Liquids. New York: John Wiley & Sons.

Chen, Da-Ren, David Y.H. Pui, and Stanley L. Kaufman [1995]
“Electrospraying of Conducting Liquids for Monodisperse Aerosol
Generation in the 4 nm to 1.8 µm Diameter Range.”
J. Aerosol Sci., 26:963-977.

Cloupeau, M. [1994]
“Recipes for Use of EHD Spraying in Cone-Jet Mode and Notes on
Corona Discharge Effects.” J. Aerosol Sci., 25:1143-1158.

Cloupeau, M. and Prunet-Foch, B. [1994]
“Electrohydrodynamic Spraying Functioning Modes: A Critical
Review.” J. Aerosol Sci., 25:1021-1036.

Cloupeau, M. and Prunet-Foch, B. [1989]
“Electrostatic Spraying of Liquids in Cone-Jet Mode.”
J. Electrostatics, 22:135-159.

Fuchs, N.A. [1963]
“On the Stationary Charge Distribution on Aerosol Particles in a
Bipolar Ionic Atmosphere.” Geophys. Pura Appl., 56:185

Grace, J.M. and Dunn, P.F. [1992]
”Electrohydrodynamic Droplet Mixing.”
J. Aerosol Sci., 23:S213-S216.

Grace, J.M. and Marijnissen, J.C.M. [1994]
“A Review of Liquid Atomization by Electrical Means.”
J. Aerosol Sci., 25:1005-1020.

Hinds, W.C. [1982]

Aerosol Technology: Properties, Behavior, and Measurement of
Airborne Particles. New York: John Wiley & Sons.

Hussin, A., H.G. Scheibel, K.H. Becker, and J. Porstendörfer [1983]
“Bipolar Diffusion Charging of Aerosol Particles I: Experimental
Results Within the Diameter Range of 4-30 nm.”
J. Aerosol Sci., 14:671.

Joffre, G.H. and Cloupeau, M. [1986]
“Characteristic Forms of Electrified Menisci Emitting Charges.”
J. Electrostatics, 18:147-161.

Michelson, D. [1990]
Electrostatic Atomization. New York: Adam Hilger.

Pui, D.Y.H., and B.Y.H. Liu [1979]
Technical paper: “Aerosol Generation and Calibration of
Instruments.” Mechanical Engr. Dept. Univ. of MN, May/June.

B–10 Model 3480 Electrospray Aerosol Generator

Righetti, P.G., G. Tudor, and K. Ek [1981]
“Isoelectric Points and Molecular Weights of Proteins: A New Table.”
Chromatographic Reviews 149, J. Chromatography, 220:115-194.

Wiedensohler, A., E. Lütkemeier, M. Feldpausch, and C. Helsper
[1986] “Investigation of the Bipolar Charge Distribution at Various
Gas Conditions.” J. Aerosol Sci., 17:413.

Willeke, K., and P.A. Baron [1993]
Aerosol Measurement: Principles, Techniques, and Applications.
New York: Van Nostrand Reinhold.

Wiedensohler, A., [1988] “Technical Note: An Approximation of the
Bipolar Charge Distribution for Particles in the Submicron Range”
J. Aerosol Sci., 10:3/387-389.

Wiedensohler, A., and H.J. Fissan [1988]
“Aerosol Charging in High Purity Gases.”
J. Aerosol Sci, Vol. 19.

Theory of Operation B–11

Index

A

AC power connector, 3-5
AC POWER IN, 2-3
acetic acid, 4-3
adjustable conductivity, 4-2
adjustable pH, 4-2
adjusting capillary tip, 5-15
aerosol exit, 3-4
aerosol exit port, cleaning, 5-4
aerosols, generating, 4-6
air flow control, B-7
air leak test, 5-8
ammonium acetate, 4-2
ammonium hydrozide, 4-3
analog output, 2-4, 3-5
ANALOG OUTPUT, 2-4
applying back pressure to capillary, 6-3

B

back panel, 3-4

drawing, 3-4

buffer solution, 4-2

preparing, 4-2

C

capillary, 3-6

adjusting position of tip, 5-15
applying back pressure, 6-3
cleaning tip, 5-14
flow characteristics, B-2
installing, 5-14
removing, 5-12
unplugging, 6-3

caution

description, xii
changing samples, 4-8
chemical buffer, 4-2
chemical safety, xiv
cleaning

aerosol exit port, 5-4

capillary tip, 5-14

Electrospray chamber, 5-6, 5-7

orifice plate, 5-3

pressure chamber, 5-10

pressure regulator, 5-19

rotameter, 5-19

viewing window lens, 5-4
CO2 flow control, B-7

IN, 15 PSI MAX, 2-4

CO

2

CO

inlet, 3-5

2

input, 2-4

CO

2

components

capillary, 3-6
Electrospray chamber, 3-6
filters, 3-8
high-voltage fitting and shield, 3-6
high-voltage supply module, 3-7
interlock switch, 3-8
internal, 3-6
main PCB, 3-7

power supply, 3-7
conductivity meter, 4-2
cone-jet mode, 4-7
connectors, 3-1
contacting TSI, v, 7-2
controls, 3-1
corona discharge mode, 4-7
current measurement, B-9
customer service, v, 7-1
cylindrical pressure chamber, 1-2

D

dripping mode, 4-7
droplet diameter

calculating, B-4

E

electrical safety, xv
Electrospray Aerosol Generator, 1-1, 5-3

AC power connector, 3-5

aerosol exit, 3-4

air leak test, 5-8

analog output, 2-4, 3-5

applications, 1-2

back panel, 3-4

drawing, 3-4
bottom view, 2-2
capillary, 3-6

adjusting position of tip, 5-15

cleaning tip, 5-14

installing, 5-14

unplugging, 6-3
changing samples, 4-8
cleaning

aerosol exit port, 5-4

Electrospray chamber, 5-6

viewing window lens, 5-4
CO2 inlet, 3-5

Input, 2-4

CO

2

connectors, 3-1
controls, 3-1
Electrospray chamber, 3-6
filter

Index-1

Electrospray Aerosol Generator (continued)

replacing, 5-19
filtered air inlet, 3-5
filtered air input, 2-4
filters, 3-8
front panel, 3-1
generating aerosols, 4-6
high-voltage fitting and shield, 3-6
high-voltage supply module, 3-7
indicators, 3-1, 3-2
inlet fitting, 5-3
interlock switch, 3-8
internal components, 3-6

drawing, 3-7
ionizer, 2-5
Ionizer retainer, 3-3
isolating leaks, 5-10
leak checking, 5-9

Electrospray chamber and pressure

chamber, 5-9
LED display, 3-1
main PCB, 3-7
maintenance, 5-1, 5-12

periodic, 5-1

schedule, 5-1
measuring and adjusting conductivity, 4-2
measuring and adjusting pH, 4-3
mounting, 2-2
operating, 4-1
operating temperature, xiv
operation, 1-2
operation unstable, 6-1
packing list, 2-1
photograph, 1-1
power connection, 2-3
power supply, 3-7
preparing a buffer solution, 4-2
preparing samples, 4-1
pressure chamber, 3-3

adjusting capillary, 5-15

adjusting platinum wire, 5-15

cleaning, 5-10, 5-11
pressure regulator

cleaning, 5-19
pressure regulator and gauge, 3-3
product overview, 1-1
proteins, 4-4
PSL, 4-4
purging the capillary, 5-1
replacement parts, 5-19
returning for service, 7-1
rotameter, 3-3

cleaning, 5-19
safety, xi

chemical, xiv

electrical, xv

labels, xi

radiation, xiii
schematic diagram, B-2
setting up, 2-1

Electrospray Aerosol Generator (continued)

shutting down, 4-8
specifications, A-1
starting up, 4-5
sucrose, 4-3
system description, B-1
theory of operation, B-1
troubleshooting, 6-1
typical solutes, 4-3
unpacking, 2-1
ventilation requirements, 2-2
viewing window, 3-3
viewing window assembly, 5-5
voltage adjustment knob, 3-2

Electrospray chamber, 3-6

cleaning, 5-6, 5-7
leak checking, 5-9
theory of operation, B-4

F

filter

replacing, 5-19
FILTERED AIR IN, 2-4
filtered air inlet, 3-5
filtered air input, 2-4
filters, 3-8
Fluka, address, 5-2
front panel, 3-1

G

generating aerosols, 4-6

H

help, xvii
high-voltage fitting and shield, 3-6
High-voltage polarity

determining, 5-17

reversing, 5-16
high-voltage supply module, 3-7

I–J–K

indicators, 3-1, 3-2
inlet fitting, 5-3
installing the capillary, 5-14
interlock switch, 3-8
internal components, 3-6

capillary, 3-6

drawing, 3-7

Electrospray chamber, 3-6

filters, 3-8

high-voltage fitting and shield, 3-6

high-voltage supply module, 3-7

interlock switch, 3-8

main PCB, 3-7

power supply, 3-7
Ionizer. (

see also Model P-2042 Nuclespot Local Air

Ionizer)

installing, 2-5

drawing, 2-6

replacing, 5-5

Index-2 Model 3480 Electrospray Aerosol Generator

Ionizer. (

isolating leaks, 5-10

see also Model P-2042 Nuclespot Local Air

Ionizer)
retainer, 3-3

(continued)

L

leaks

isolating, 5-10

LED displays, 3-1

M–N

main PCB, 3-7
maintenance, 5-1

periodic, 5-1
pressure regulator, A-2
removing capillary, 5-12
rotameter, A-3
schedule, 5-1
special, 5-12

manual

about, xvii
manual history, iv
measuring and adjusting conductivity, 4-2
measuring and adjusting pH, 4-3
Model 3074B Filtered Air Supply, 2-4
Model 3480 Electrospray Aerosol Generator. (

Electrospray Aerosol Generator)
Model P-2042 Nuclespot Local Air Ionizer, xiii, xiv,

2-5, 3-3

replacing, 5-5
monodisperse aerosol

size range, 1-1

see

O

operation, 1-2, 4-1

preparing a buffer solution, 4-2

preparing samples, 4-1
operation unstable, 6-1
orifice plate, cleaning, 5-3

purging the capillary, 5-1, 5-2

R

radiation

safety, xiii

references

theory of operation, B-9
replacement parts, 5-19
replacing filter, 5-19
returning for service, 7-1
rotameter, 3-3

cleaning, 5-19

maintenance, A-3

S

safety, xi

chemical, xiv

electrical, xv

labels, xi

radiation, xiii
service policy, v
setting up the Generator, 2-1
shutting down the Electrospray, 4-8
specifications, A-1
starting up the Electrospray, 4-5
sucrose, 4-3
Swagelok, 2-4, 3-4

T

theory of operation, B-1

Electrospray chamber, B-4

references, B-9
troubleshooting, 6-1
TSI

contacting, v, 7-1, 7-2

getting help, xvii

submitting comments, xviii
Tween, 5-2
typical solutes, 4-3

P–Q

packing list, 2-1
pH meter, 4-3
Polonium-210, xiii, 2-1, 2-5, 3-3
power connection, 2-3
power supply, 3-7
pressure chamber, 3-3

adjusting capillary, 5-15
adjusting platinum wire, 5-15
cleaning, 5-10, 5-11
leak checking, 5-9

pressure gauge

checking the zero, 2-3

pressure regulator

cleaning, 5-19

maintenance, A-2
pressure regulator and gauge, 3-3
proteins, 4-4
PSL, 4-4
pulsating mode, 4-7

U

ultrapure water, 4-2
unpacking the Generator, 2-1
unplugging capillary, 6-3
unstable operation, 6-1

V

ventilation requirements, 2-2
viewing window, 3-3

cleaning lens, 5-4
viewing window assembly, 5-5
volatile solution, 4-2
voltage adjustment knob, 3-2
voltage measurement, B-9

W–X–Y–Z

warning

description, xiii
water, ultrapure, 4-2

Model 3480 Electrospray Aerosol Generator Index-3

Index-4 Model 3480 Electrospray Aerosol Generator

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