Valco Instruments Co. Inc.
Pulsed Discharge
Detector
Model D-2-IM
Instruction Manual
Valco Instruments Co. Inc.
800
·
367
·
·
688
·
688
8424 sales
·
9345 tech
·
8106 fax
713
713
valco@vici.com
Valco International
Schenkon, Switzerland
Int + 41 · 41 · 925
Int + 41 · 41 · 925
info@vici.ch
·
6200 phone
·
6201 fax
D2-IM.p65
©2011 9/11
Printed in USA
This page intentionally left blank for printing purposes
Table of Contents
Introduction
System Requirements
Installation
Description and Operating Principles .......................................................................................... 1
Safety Notes and Information ................................................................................................... ...... 2
Symbols
Installation Category
Safety
Maintenance
Components of the Detector System .......................................................................................... 4
Description of Controls ..................................................................................................................... 4
Components Not Included with the Detector System .......................................................... 8
System Purity ........................................................................................................................................ 8
Specifications ....................................................................................................................................... 9
Purity Specifications ........................................................................................................................... 9
GC Column Selection ..................................................................................................................... 10
General Precautions ........................................................................................................................ 11
Mounting the Detector on the GC ............................................................................................. 11
Gas Connections .............................................................................................................................. 12
Installing and Purging the Gas Regulator ....................................................................... 12
Installing and Purging the Helium Purifier .................................................................... 13
Connecting the Discharge Gas to the Detector .......................................................... 14
Column Connection ........................................................................................................................ 14
Testing for Leaks ............................................................................................................................... 14
Electrical Connections .................................................................................................................... 15
Initial Power-Up ................................................................................................................................16
Troubleshooting High Background Current ............................................................................. 17
Checking for Leaks in the Discharge Gas Plumbing .................................................. 17
Column Bakeout Precautions ........................................................................................... 17
Warranty ..................................................................................................................................................... 18
Detector Performance Log .................................................................................................................... 19
This page intentionally left blank for printing purposes
Introduction
Description and Operating Principle
1
The pulsed discharge detector Model D-2-IM is a universal helium photoionization
detector optimized for trace level work with micropacked and capillary columns.
A schematic representation is shown in Figure 1.
As the name implies, a stable, low power, pulsed DC discharge in helium is utilized
as the ionization source. Elutants from the column, flowing counter to the flow of
helium from the discharge zone, are ionized by photons from the helium discharge
above. Resulting electrons are focused toward the collector electrode by the two
bias electrodes.
The principal mode of ionization is photoionization by radiation arising from the
transition of diatomic helium
This is the well-known Hopfield emission. The photon energy from the He
He
1
+
(
∑
)
A
u
2
to the dissociative 2He(1S
1
) ground state.
2
continuum is in the range of 13.5 eV to 17.7 eV.
The PDHID is essentially non-destructive (0.01 - 0.1% ionization) and highly
sensitive. The response to organic compounds is linear over five orders of
magnitude with minimum detectable quantities (MDQs) in the low or sub
picogram range. The response to fixed gases is positive (the standing current
increases), with MDQs in the low ppb range.
HELIUM INLET
DISCHARGE ZONE
SPRING WASHERS
DISCHARGE ELECTRODE
QUARTZ
GROUND
BIAS ELECTRODE
COLLECTOR ELECTRODE
BIAS ELECTRODE
INSULATOR
SAPPHIRE
INSULATORS
CAPILLARY COLUMN
VENT
COLUMN INLET
Figure 1: Schematic of the D-2-IM detector
Introduction
2
The PDHID response is universal except for neon, which has an ionization potential
of 21.56 eV. Since this potential is close to the energy of the He* metastable
(19.8 eV ) but greater than the photon energy from the He2 continuum, neon
exhibits a low ionization efficiency and low detector response. (NOTE: Valco
makes an enhanced mode detector for neon. Consult the factory for information.)
Safety Notes and Information
Symbols
HIGH VOLTAGE
Voltages presenting the risk of electric shock are present in several
places in the equipment. Avoid contact with hazardous live parts.
Do not probe into openings or attempt to defeat safety mechanisms.
HOT SURFACE
The surface of the detector body may be hot while in operation
(possibly in excess of 250°C). Caution should be observed.
ATTENTION
Refer to the manual.
PROTECTIVE EARTH
This internal connection provides protection against electric shock
from mains voltages and should not be removed.
Installation Category
This equipment has been designed for installation category (overvoltage category)
II, pollution degree 2. It has been approved for use only in heavy industrial environments and may not be used in the residential, commercial, or light-industrial
environment.
Introduction
Safety
This instrument has been designed and tested in accordance with the product
safety standard, EN61010. It has left the factory in a safe condition. This instruction
manual contains important information and warnings which must be followed by
the user to insure safe operation and to retain the instrument in a safe condition.
The case, chassis, and measuring terminals are connected to the protective earth
contact of the mains inlet. The instrument operates with a three-conductor power
cord having a protective earthing conductor and a plug with an earthing contact.
The mains (line) plug shall only be inserted in a socket outlet provided with a
protective earth contact. The protective action must not be negated by the use
of an extension cord without a protective conductor. Use only with an approved
mains supply cord having a rating of 2A, 250V, or greater. Do not use this equipment in a manner not specified herein.
CAUTION: During normal operation, the detector produces
ultraviolet energy (UVA, UVB), some of which may be
emitted. Do not watch the arc without eye protection.
3
Maintenance
The exterior of the instrument should be cleaned regularly with a dusting brush. If
necessary, the casing can be cleaned with a moistened cloth (99% water + 1% mild
detergent). Spirit or petroleum ether can be used to remove greasy dirt. Any other
cleaning agents can attack the plastic and painted surfaces.
Under no circumstances should the cleaning fluid get into the instrument.
Petroleum ether is flammable, and care should be taken in its use. Under no
circumstances should the detector be disassembled for cleaning. The components
of the detector are assembled with special tooling and held under considerable
force. Disassembly of the detector may present a safety hazard and will result in
its destruction.
Introduction
4
Description Quantity Product number
Detector cell, PDHID D2 Mini ionization 1 PD-D2-IM
Pulse supply module 1 PD-M2
Includes: Cable, controller to pulse supply 1 I-23477
Controller unit with power cord 1 PD-C2
Includes: Cable, computer (unattenuated) output 1 I-23136
Helium purifier, miniature version 1 HPM
Helium purifier, standard 1 HP2
Instruction manual 1 MAN-PDD-M
Fittings kit 1 PD-KIT-IM
Includes: 1/16" gold-plated ferrule 5 ZF1GP
Cable, recorder (attenuated) output 1 I-23483
1/32" Vespel ferrule 5 ZF.5V
Fused silica adapter, 40 mm to 1/32" 5 FS.4
Fused silica adapter, 50 mm to 1/32" 5 FS.5
1/16" union 2 ZU1MS6
1/16" tee 1 ZT1
Restrictor, 10 cc/min @ 60 psi He 1 TGA-R-10F60P
Table 1:
Components of the D-2-IM system
Components of the Detector System
Components of the detector system are listed in Table 1. Check the contents of
the packages to verify that everything is present. Contact the factory if anything is
missing or damaged. (NOTE: damaged shipments must remain with the original
packaging for freight company inspection.)
Description of Controls
Controls and connectors are indicated in Figure 2.
MAINS switch
Controls mains (line) voltage to the controller unit. When this switch is on ( | ),
the unit is operational except for the pulse supply (see the next paragraph). The
detector heater will operate (if connected) and high voltage is present on the bias
cables.
DISCHARGE switch and indicator
Controls power to the pulse supply module. When the switch is on and the module
is connected, high voltage is generated by the unit and is present at the detector
electrodes. The indicator will not light if the detector is in the standby mode, or if
the pulse supply is not connected to the controller. The indicator flashes until the
discharge has been established, then glows steadily.
Introduction
TEMPERATURE control and indicator
Sets the temperature (°C) of the detector heater block. The indicator is steadily on
when maximum power is being applied to the heater, steadily off when no power
is applied, and regularly blinking on/off when the set temperature has been
established.
Note that due to the fail-safe mechanism designed into the temperature controller,
the heater will not operate if mains power is applied before the heater is connected
or if the detector is too cold (< 0°C). If the heater is disconnected with mains on,
the unit must first be turned off to restore control of the heater; if the unit is
operated in a very cold environment, the detector should first be gently warmed
without power applied.
The fail-safe mechanism will also act under any condition resulting from loss of
control (e.g., over-heating, RTD failure, etc.). If proper procedures have been
followed and the controller will not heat the detector, there is cause to suspect that
the fail-safe mechanism has been activated. Consult the factory or an authorized
representative. Note that the maximum temperature for operation of the
PD-D2-IM is 400°C.
5
Heater control may be lost during periods of fast
electrical transients. The unit will self-recover.
MODE switch
Not used with this detector, since it is in the PDHID mode at all times.
RANGE switch
Determines the full-scale range of the electrometer: 100 nA @ 1X or 10 nA @ 10X.
CURRENT switch
Sets the standing current in PDECD mode. Not used with this detector, since it is in
the PDHID mode at all times.
ATTENUATION control
Determines the attenuation factor for the recorder output.
ZERO push button
Offsets the output signal to zero volts by a measurement of the standing current.
The offset is applied to the output when the button is released. Once set, the
offset is not changed unless the unit is re-zeroed or the mode is changed. To
remove any applied offset and restore the unit to an un-zeroed condition, toggle
the MODE or RANGE switch. The function of this control is duplicated by an
external logic connection; see UNATTENUATED OUTPUT on page 7.
Display
Indicates standing current. In the un-zeroed PDHID mode, the display indicates the
instantaneous signal current in nA. After zeroing, the display indicates the standing
current by which the signal is offset.
Introduction
6
TEMPERATURE
CONTROL
TEMPERATURE
INDICATOR
DISCHARGE
INDICATOR
DISCHARGE
SWITCH
160
120
80
200
240
40
DETECTOR TEMP .
400
DISCHARGE
280
MODE
SWITCH
PDECD
RANGE
SWITCH
1X
CURRENT
SWITCH
INCREASE
320
360
PDHID
MODE
10X
RANGE
DECREASE
CURRENT
PULSED DISCHARGE CONTROLLER
2
1
V ECD
nA HID
DISPLAY
16
8
4
ATTENUATION
6432
ZERO
128
256
512
1024
ATTENUATION
CONTROL
ZERO PUSH
BUTTON
HEATER
OUTPUT
PULSE
SUPPLY
HEATER
VALCO INSTR UMENTS CO . INC .
115/230V ~ 175VA MAX
ATTEN
PULSE
SUPPLY
+
SHIELD
ATTENUATED
OUTPUT
MODEL PD-C2
50/60 Hz
OUTPUTS
-
UNATTEN
10V-SHIELD
1V
COM
ZERO
UNATTENUATED
OUTPUT
MAINS INPUT
T2.0A
250V
MAINS
INPUT
WARNING: FOR CONTINUED PROTECTION AGAINST FIRE
HAZARD, REPLACE FUSE WITH SAME TYPE AND RATING.
ATTENTION: UTILISER UN FUSIBLE DE RECHANGE DE MÊME TYPE.
DETECTOR
INPUT: 15V MAX. CAT
FUSE MAINS
ELECTROMETER
BIAS-B
BIAS-A
SWITCH
Figure 2: Controls and connections
on front (top) and back panels of the control module
Introduction
ATTENUATED OUTPUT connector
Normally connected to a strip chart recorder. This output has an unattenuated
range of 0 - 10V, and an internal signal reference (-) at zero volts. For best noise
performance, the shield (earth) and signal reference (-) should not be connected
together. The signal from this output is scaled by the attenuation factor set on the
front panel.
UNATTENUATED OUTPUT connector
Normally connected to a data acquisition system or other recording means. For
convenience, a full-scale 0 - 10V output and a 1/10 scale 0 - 1V output are provided,
with an internal signal reference (-) at zero volts. For best noise performance, the
shield (earth) and signal reference (-) should not be connected together. The
internal impedance of these outputs is 1000 ohms. The connection marked ZERO
is a low-true, 5V logic-level input which duplicates the function of the front-panel
ZERO; connection of this input to COM through either a relay contact or logic gate
is equivalent to pressing the ZERO button.
HEATER OUTPUT connector
For connection to the detector heating system.
ELECTROMETER INPUT cable
For connection to the collector electrode of the PD detector. The full-scale input
current is determined by the RANGE switch. Input voltages in excess of 15 VDC
may result in damage to the electrometer.
7
BIAS A, B OUTPUT cables
For connection only to the bias electrodes of the PD detector in the manner
described on page 15 under the heading “Electrical Connections”. These outputs
supply high voltages when power is applied to the unit, and caution should be
observed when connecting or disconnecting these cables.
NOTE: These terminals are for connection only to
equipment having no accessible live parts. Insulation
of external circuits to which these are connected must
meet the requirements of EN61010 for 220 VDC working
voltage.
8
System Requirements
Components Not Included with the Detector System
System Purity
• Helium (99.999% purity) and other support gases
• Ultra high purity grade gas pressure regulator with stainless steel diaphragm
• Any special adapters required for connection to the gas regulator
• Flow measuring device
Discharge/Carrier Gas Considerations
The performance of the detector is adversely affected by the presence of any
impurities in the gas streams (carrier, discharge, or dopant). We recommend that a
quality grade of helium 5.0 (99.999% pure or better) be used at all times. Major gas
suppliers offer research grade helium (99.9999% pure) which is particularly low in
fixed gas impurities and should give good results in a clean system, but even the
highest quality carrier gas may contain some water vapor and fixed gas impurities;
hence a helium purifier is included as part of the detector system. The discharge
gas must always be run through the helium purifier.
Whenever a new batch of discharge gas is received, we recommend performing
a blank GC analysis of the gas in the PDHID mode to detect and identify the
presence of any impurities. Gas purity requirements are specified in the next
section.
Tubing
Standards of cleanliness that are suitable for many GC applications may be totally
inadequate for the sensitive PDHID work. All surfaces that contact the gas stream
must be glass or stainless steel. Do not use copper tubing or brass fittings. All
tubes must be thoroughly cleaned and baked before use.
Flow Controllers
The use of valves or flow controllers in which the gas stream is exposed to any
polymer-based packing or lubricating material is to be particularly avoided.
Pressure Regulators
We recommend commercial “ultra-pure” grade regulators with stainless steel
diaphragms. Regulators with diaphragms made of neoprene or other elastomers
should never be used.
Specifications
Mains (line): 115/230 V~50/60 Hz, 175 VA
Fuse: 2 A, time-delay, 5 x 20 mm
Pressure: 6.9 kPa (1 psi) operating, 6.9 MPa (1000 psi) max.
Max temperature: 400°C
Heater power: 60 W max., 48 V, PWM
Sensitivity
Range
System Requirements
9
working
10X range: 1.0 V/nA
1X range: 0.1 V/nA ± 1%*
10X: 10 nA full-scale
1X: 100 nA full-scale*
Noise
1X: 20 fA/√Hz (referred to the input), 0.1 - 10 Hz*
10X: 5 fA/√Hz (referred to the input), 0.1 - 10 Hz
Risetime: 10 msec, 10% = 90%*
Output impedance: < 1 Ω , attenuated
*Controller only, PDHID mode, 10 V unattenuated output
Purity Specifications
Helium (discharge and carrier gas) must have a minimum purity of 99.999%, with
< 20 ppm Ne impurity. For trace analysis of fixed gases, we strongly recommend
99.9999% purity He with < 0.5 ppm Ne.
1 KΩ, unattenuated, 1 V, 10 V
System Requirements
10
GC Column Selection
To prevent detector contamination, we strongly
recommend disconnecting the column from the
detector during column bakeout procedures.
The PD-D2-IM is optimized for micropacked (1/16" and smaller) and capillary /PLOT
columns. The column tubing must be thoroughly cleaned and baked before the
column is packed. Even when the best care is taken in column tubing cleaning and
in the support and stationary phase selection, a new column will often bleed
compounds, resulting in a considerable increase in the detector baseline. This
initial bleed will usually be reduced to acceptable levels after the column is
conditioned with clean carrier gas flow for several hours at the recommended
bakeout temperature.
Installation
General Precautions
11
The detector is usually mounted on top of the GC column oven. The cabling as
supplied requires the discharge module to be located within 0.6 m (2') of the
detector and the controller to be within 1 m (3.5') of the detector and discharge
module. The power cord for the controller is 1.8 m (6') long, and the signal output
cables (attenuated and unattenuated) are 1.2 m (4') long.
• Do not use plastic/polymer or copper tubes for gas handling and inter-
connectons. Use only stainless steel tubing with Valco gold-plated ferrules.
• Do not turn the unit on until the helium discharge gas is flowing through the
detector.
• Do not shut off or disconnect the discharge gas when the detector is hot, even
if the unit is turned off. Turn off both power switches (front and back of the
controller) and allow the detector to cool down naturally before disconnecting
or shutting off the discharge gas.
• Do not cover the unit with materials or devices which would restrict air
circulation.
• Position the controller unit where the mains switch on the rear panel can
be reached easily.
Mounting the Detector on the GC
Vertical Mounting
Most GCs have an existing opening which will allow the PDD to sit vertically on top
of the column oven with the column inlet tube extending into the oven. The vent
tube can either extend into the oven or be carefully bent near the base to remain
outside the oven. If you are replacing an existing detector, you can usually just
remove it and set the PDD in its place. If not, use a drill or chassis punch to drill a
hole of the proper size, and set the detector in position.
While trying to match the mounting holes of the base plate to every GC on the
market is impractical, we have located the mounting holes so that at least two of
them will coincide with existing holes on the GC. If you had to drill a new hole to
mount the PDD, you will have to drill new mounting holes as well. Orient the
detector to allow for easy cable and gas connections.
Horizontal Mounting
Some older GCs have access to the column oven through the side of the GC. This
does not present a problem as far as operation of the PDD is concerned. Drill a
hole at the appropriate location, orient the detector for convenient connection, and
mark the position of the mounting holes. Drill the mounting holes and secure the
detector to the side of the GC with four sheet metal screws (not supplied).
Installation
12
Gas Connections
Remember these three points discussed earlier: (1) all surfaces that contact the
gas stream must be glass or stainless steel; (2) do not use copper tubing or brass
fittings; and (3) all tubes must be thoroughly cleaned and baked before use. The
installation instructions below assume that the detector discharge will be supplied
from a nearby cylinder of helium of the proper purity. If your installation is different, you may need to modify the instructions appropriately. A number of Valco
fittings have been supplied in the fittings kit to handle different situations.
Figure 3 illustrates gas connections for a typical PD-D2-IM detector system.
Since the distance from the helium supply to the GC varies from installation to
installation, we do not supply tubing to go from that point to the GC.
TGA-R-10F60P
RESTRICTOR
(10 mL/min minimum)
DISCHARGE GAS
INLET
TEE
(ZT1)
HELIUM
PURIFIER
DISCHARGE GAS
(99.999% He)
VENT
COLUMN
INLET
COLUMN INJECTOR
GAS CHROMATOGRAPH
Figure 3: Gas connections for a PD-D2-IM system
Installing and Purging the Gas Regulator
1. Make sure the on/off valve on the helium cylinder is completely closed. Screw
the CGA fitting nut of the regulator into the helium cylinder. Go beyond fingertight, but do not tighten the nut all the way – some leakage is required for the
purging operation.
2. Turn the output pressure regulating knob completely counterclockwise.
3. Open the cylinder on/off valve slightly and quickly close it again.
4. Adjust the tightness of the regulator connecting nut to allow a pressure reduction of ~690 kPa/sec (100 psi/sec). With a new bottle, the gauge should start
out at about 14 MPa (2000 psi).
5. When the pressure drops into the 1.4 - 3.4 MPa (200 - 500 psi) range, open the
cylinder on/off valve slightly and quickly close it again.
6. Repeat Step 5 eight or ten times to be certain that all the air is purged. On the
final purge, tighten the regulator connecting nut very securely as the pressure
approaches the 2.1 - 3.4 MPa (300 - 500 psi) range.
7. Open the cylinder valve to pressurize the regulator once again. Close the valve
and observe the needle of the high pressure gauge for 15 minutes. If it doesn’t
move, there is no critical leak on the high pressure side of the regulator.
EZR21
Installation
13
CAUTION: Never use leak detecting fluids on any part of
this system.
Installing and Purging the Helium Purifier
1. If the pressure regulator has a 1/8" male cone-type outlet port, install the Valco
1/8" external to 1/16" internal reducer (EZR21); if it has a 1/4" male cone-type
outlet port, install the Valco 1/4" external to 1/16" internal reducer (EZR41). For
other regulator outlet fittings, a wide variety of Valco adapters are available.
2. Remove the cap from the inlet tube of the Valco helium purifier and insert the
tube fitting into the 1/16" reducer port. (Keep the outlet tube capped.) Use a
1/4" wrench to turn the nut one-quarter turn past the point where the ferrule
first starts to grab the tubing. Do not remove the fitting. When made up
properly, it should be leak-tight.
3. Turn the output pressure regulating knob clockwise until the gauge registers
345 KPA (50 psi).
4. Allow five minutes for equilibration, then turn the regulating knob all the way
counterclockwise.
5. Observe the needle of the output pressure gauge for 15 minutes. There will be
a slight initial drop, but if it doesn’t move after that, consider that all the connections are tight.
6. If necessary, use an electronic leak detector to locate any leaks. If a leak
detector is not available, tighten all the fittings (including the output pressure
guage), and repressurize the system for another test.
CAUTION: Never use leak detecting fluids on any part of
this system.
7. Upcap the outlet tube of the purifier and purge the system for 15 to 30 minutes
at 60 - 80 mL/min to eliminate air from the purifier getter material.
Installation
14
Connecting the Discharge Gas to the Detector
1. If you are supplying the GC from the helium purifier, use the Valco tee (ZT1).
Otherwise, use one of the Valco 1/16" unions (ZU1) to connect the outlet tube
of the purifier to the inlet of the supplied discharge gas restrictor (TGA-R-10F60P).
2. Connect the outlet end of the restrictor to a flow measuring device and adjust
the helium pressure to obtain a flow of and ~10 mL/min for the PD-D2-IM.
3. After setting the flow rate, connect the outlet of the restrictor to the discharge
gas inlet tube at the top of the detector.
Column Connection
The type of column used will determine the parts needed to connect the column.
If a metal capillary or micropacked column is the column of choice, then a packed
column adapter (I-23642-D2-IM) is required. This inlet provides a 1/16" fitting detail
for external connection of the column to the detector with the appropriate ferrule
or fused silica adapter. The same adjustability is offered for column insertion depth
using this adapter.
If a fused silica capillary column is used, the outlet end of the column is inserted
directly into the column at an insertion depth of 7 cm. Instructions below are for
the use of fused silica capillary column.
1. Make a mark on the column 7 cm from the end.
2. Remove the knurled nut and plug from the column inlet manifold at the bottom
of the detector. Slide the nut over the end of the column, followed by the
appropriate column ferrule (FS.4 or FS.5, or ZF.5V for megabore).
3. Insert the column through the column inlet manifold at the bottom of the
detector. Slide it in until the mark is flush with the surface of the knurled nut,
and secure the column by tightening the knurled nut fingertight only.
Testing for Leaks
It is critical for the system to be leak-tight, and an additional check at this point can
save many headaches later on. To test for leaks:
1. Cap the vent outlet tube.
2. Pressurize the entire system with helium to 138 kPa (20 psi).
3. If the system does not hold pressure, check all the fittings with an electronic
helium leak detector. DO NOT use leak detecting liquids.
4. Tighten fittings as required. (Further leak testing is described on page 17 in the
section entitled “Checking for Leaks in the Discharge Gas Plumbing”).
Electrical Connections
1. Referring to Figure 4 as necessary, connect the bias and electrometer cables
as follows: the BIAS-B cable to the top electrode (closest to the discharge
electrodes), the electrometer cable (ELECT) to the middle, and the BIAS-A
cable to the bottom electrode.
2. Connect the high-voltage cable from the detector to the pulse supply, and
connect the pulse supply cable between the back of the controller and the
pulse supply. Connect the heater cable from the detector to the back of the
controller.
Installation
15
CAUTION: Do not use a wrench to tighten the SMC
connectors on the bias and electrometer cables.
Connections should be fingertight only.
RECORDER
DISCHARGE
MODULE
ATTENUATED
OUTPUT
SHIELD
+
RED
BLACK
GREEN
WHITE
HIGH
VOLTAGE
HEATER CABLE
FROM DETECTOR
CONTROLLER
(Rear panel)
RED
BLACK
WHITE
GREEN
BROWN
BLUE
ORANGE
YELLOW
0 - 10 V
Common
0 - 1 V
Shield
COM
SET
BIAS-B
ELECT.
BIAS-A
UNATTENUATED
OUTPUT
AUTO
ZERO
COMPUTER OR
INTEGRATOR
Figure 4: Electrical connections
Installation
16
Initial Power-Up
1. If it is not already there, set the MODE switch on the front of the controller to
PDHID.
2. Set the discharge gas flow as specified in on page 14 in the section entitled
“Connecting the Discharge Gas to the Detector”.
CAUTION: Always make sure that discharge gas is flowing
before powering up the detector.
3. Apply power to the helium purifier.
4. Turn on the MAINS switch located on the back of the controller.
5. Set the detector temperature to 100°C with the TEMPERATURE control k nob.
Allow time for the detector and helium purifier to reach temperature.
6. Turn on the DISCHARGE switch, located on the front of the controller. The
discharge should start within five minutes. (Once a system has been up and
running, the discharge will start within a few seconds.)
In a clean system, the discharge will have a peach/pink color. A purple discharge
indicates impurities and/or leaks in the discharge gas stream.
7. Check the detector standing/background current, indicated in the LED DISPLAY
on the controller, and record it in the Detector Performance Log on the last page
of this manual. The optimum detector background current is 0.5 to 1.5 nA. The
initial value may be higher, but as the detector bakes out at its operating
temperature, the background current should decrease to the optimum value.
8. The recommended detector temperature is 20°C above the column temperature, with a minimum of 100°C. Set the detector to the operating temperature
required for the intended analysis. When the detector has reached the set
temperature, read and record the standing current.
9. Install the column as described on page 14, leaving the oven at ambient
temperature. Start carrier flow, then read and record the standing current.
The difference between this reading and the one previous is the ionization of
the combined impurities in and eluting with the carrier gas. The smaller the
difference, the better the quality of the gas exiting the column.
10. Set the column oven to the temperature required for the intended analysis.
When the oven reaches the set temperature, read and record the standing
current.
The difference from the previous reading is the ionization of the column
bleed. The smaller the difference, the better the column is conditioned.
NOTE: Some stationary phases will have a higher bleed than others, but
are still suitable for this detector. However, the lower the bleed, the lower
the chances of contaminating the detector cell.
From this point, the standing current should be observed and logged after any
system change. In addition, logging the standing current (with and without the
column) on a regular basis is an effective monitor of system integrity (leaktightness and cleanliness). We also recommend tracking the internal standard
(quantity on column/area count) for sensitivity continuity.
Troubleshooting High Background Current
If the background current does not drop below 2 nA even after a 12 hour bakeout,
there is either a leak in the system or the column effluent is not clean. To see if the
high background current is due to the column:
1. Make sure the controller is in the un-zeroed condition. (Refer to the discussion
about the ZERO push button on page 5.)
2. Completely disconnect the column from the column inlet tube, leaving the inlet
open.
3. Watch the detector standing/background current, indicated in the controller
DISPLAY. If the current remains high, then either the system has a leak in the
discharge gas supply line or the discharge gas has impurities in it. Proceed to
the next section, “Checking for Leaks in the Discharge Gas Plumbing”. If the
current decreases dramatically, then either the carrier gas supply has leaks
and/or contaminants, or the column is the source of contamination and needs
a bakeout. Read the “Column Bakeout Precautions” below before proceeding.
Installation
17
Checking for Leaks in the Discharge Gas Plumbing
Leaks can be detected with hydrogen. A small lecture bottle of hydrogen with a
regulated flow of 10-15 mL/min through a small outlet tube is all that is required.
(This method can only be used to detect leaks on the discharge gas side of the
plumbing and between the column and detector inlet.)
1. Make sure the controller is in its un-zeroed condition. (Refer to the discussion
about the ZERO push button on page 5.)
2. Hold the hydrogen outlet tube at a fitting connection for ten seconds while
monitoring the standing current display on the controller.
3. If the current remains the same, proceed to the next fitting. If the current
increases, there is a leak at that connection. Tighten the fitting and test it again,
repeating as necessary until there is no change in the standing current.
4. Repeat the test for every fitting in the discharge gas plumbing.
5. Reinstall the column according to the instruction on page 14. When the
standing current reaches an acceptable level, the detector is ready for use.
Proceed to the next chapter, “Mode Selection and Setup”. If the current stays
high, use this method to check for leaks at the column/detector connection.
Column Bakeout Precautions
To prevent detector contamination, we strongly recommend disconnecting the
column from the detector during column bakeout procedures.
When the column in reinstalled after bakeout (refer to page 14 if necessary), the
standing current should be at an acceptable level. If you have exhausted these
troubleshooting methods and the standing current is still high, consult the factory.
18
Warranty
This Limited Warranty gives the Buyer specific legal rights, and a Buyer may also
have other rights that vary from state to state. For a period of 365 calendar days
from the date of shipment, Valco Instruments Company, Inc. (hereinafter Seller)
warrants the goods to be free from defect in material and workmanship to the
original purchaser. During the warranty period, Seller agrees to repair or replace
defective and/or nonconforming goods or parts without charge for material or
labor, or, at the Seller’s option, demand return of the goods and tender repayment
of the price. Buyer’s exclusive remedy is repair or replacement of defective and
nonconforming goods, or, at Seller’s option, the repayment of the price.
Seller excludes and disclaims any liability for lost profits, personal injury,
interruption of service, or for consequential incidental or special damages
arising out of, resuiting from, or relating in any manner to these goods
This Limited Warranty does not cover defects, damage, or nonconformity resulting
from abuse, misuse, neglect, lack of reasonable care, modification, or the attachment of improper devices to the goods. This Limited Warranty does not cover
expendable items. This warranty is VOID when repairs are performed by a
nonauthorized service center or representative. For information about authorized
service centers or representatives, write Customer Repairs, Valco Instruments
Company, Inc, P.O. Box 55603, Houston, Texas 77255, or phone (713) 688-9345.
At Seller’s option, repairs or replacements will be made on site or at the factory.
If repairs or replacements are to be made at the factory, Buyer shall return the
goods prepaid and bear all the risks of loss until delivered to the factory. If Seller
returns the goods, they will be delivered prepaid and Seller will bear all risks of loss
until delivery to Buyer. Buyer and Seller agree that this Limited Warranty shall be
governed by and construed in accordance with the laws of the State of Texas.
The warranties contained in this agreement are in lieu of all other warranties
expressed or implied, including the warranties of merchantability and fitness for
a particular purpose.
This Limited Warranty supercedes all prior proposals or representations oral or
written and constitutes the entire understanding regarding the warranties made by
Seller to Buyer. This Limited Warranty may not be expanded or modified except in
writing signed by the parties hereto.
Detector Performance Log
In addition to the occasions indicated in the Comments area of the table below, (see Initial Power-Up, page
16), the standing current should be observed and logged after any system change. Logging the standing
current (with and without the column) on a regular basis is also an effective monitor of system integrity
(leaktightness and cleanliness). To check sensitivity continuity, we recommend tracking the internal standard
(quantity on column/area count). Additional log pages can be downloaded from the support/manuals section
of www.vici.com.
19
Detector Model: Serial Number: Date of purchase:
Date
Operator Column
D-2-I M
Detector
temp
(°C)
Initial power-up (IPU) 100
IPU, detector to analysis temp
IPU, column installed Ambient
IPU, column to analysis temp
temp
(°C)
Noise
level
SampleComments
Standing
current
(nA)
Loading...