Valco Instruments Co. Inc.
Introduction
Description and Operating Principles ............................................................ 1
Safety Notes and Information........................................................................ 2
Components of the Detector System ............................................................ 3
System Requirements................................................................................... 4
Installation
General Precautions...................................................................................... 6
Mounting the Detector on the GC ................................................................. 6
Pulser Module Installation ............................................................................. 6
Gas Connections........................................................................................... 7
Installing and Purging the Gas Regulator .............................................. 7
Installing and Purging the Helium Purifier.............................................. 8
Connecting the Discharge Gas to the Detector..................................... 8
Detector Electrical Connections .................................................................... 9
Initial Po wer-Up ........................................................................................... 10
Capillary Column Connection ...................................................................... 11
Pac ked Column Connection ........................................................................ 11
Testing for Leaks ......................................................................................... 12
Pulsed Discharge Detector
Models D-4-I-TQ-R
and D-4-I-TQI-R
Instruction Manual
Mode Selection and Setup
Helium Ionization Mode............................................................................... 13
Selective Photoionization Mode................................................................... 13
Troubleshooting
High Background Current............................................................................ 15
Low Sensitivity ............................................................................................ 15
No Peaks..................................................................................................... 15
High Noise Level ......................................................................................... 16
Performing a Hydrogen Leak Test ............................................................... 16
Warranty ............................................................................................................ 17
Detector Performance Log ................................................................................. 18
Valco Instruments Co. Inc.
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d4_therm.P65
© 2002 Rev . 1/02
Printed in USA
Introduction
Description and Operating Principle
1
The PD-D-4-I-TQI-R and PD-D-4-I-TQ-R are non-radioactive pulsed discharge
ionization detectors (PDIDs) optimized for ThermoFinnigan GCs. A schematic
representation of the basic D4 detector is shown in Figure 1.
The D4 utilizes a stable, lo w pow er, pulsed DC discharge in helium 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
He
1
+
(
∑
)
A
u
2
to the dissociative 2He(1S
1
)
ground state. This is the well-known Hopfield emission. The photon energy
from the He2 continuum is in the range of 13.5 eV to 17.7 eV.
The D4 is essentially non-destructive (0.01 - 0.1% ionization) and highly
sensitive. The response to organic compounds is linear o v er five orders
of magnitude with minimum detectable quantities (MDQs) in the low
picogram range. The response to fix ed gases is positiv e (the standing
current increases), with MDQs in the low ppb range.
Detector response is universal except f or 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.
When a dopant is added to the discharge gas, the D4 also functions
as a selective photoionization detector . (Suitable dopants include Ar fo r
organic compounds, Kr for unsaturated compounds , or Xe f or polyn uclear
aromatics.)
GROUND PIN
DISCHARGE REGION
HELIUM INLET
HIGH VOLTAGE
SAPPHIRE INSULATORS
BIAS ELECTRODE
CAPILLARY COLUMN
VENT
COLUMN INLET
Figure 1: Schematic of the D4 detector
COLLECTOR ELECTRODE
Introduction
2
Helium Ionization (PDHID) Mode
The PDHID is essentially non-destructive (0.01 - 0.1% ionization) and highly
sensitive. The response to organic compounds is linear o v er fiv e orders of
magnitude with minimum detectable quantities (MDQs) in the low or sub
picogram range. The response to fix ed gases is positiv e (the standing
current increases), with MDQs in the low ppb range.
The PDHID response is universal except f or 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 He
continuum, neon exhibits a low ionization efficiency and lo w detector
response.
2
Photoionization (PDPID) Mode
Changing the discharge gas from pure helium to helium doped with argon,
krypton, or xenon changes the discharge emission profile, resulting in
resonance atomic and diatomic emissions of the rare gas added. Response
is limited to sample compounds with ionization potentials less than or equal
to the dopant gas emission energy. In this configuration, the detector is
essentially functioning as a specific photoionization detector for selective
determination of aliphatics, aromatics, and amines, as well as other species.
Since there is no lamp or window , sensitivity will not change with time.
Safety Notes and Information
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.
Symbols
HIGH VOL T A GE
V oltages presenting the risk of electric shock are present in
sever al places in the equipment. Av oid contact with hazardous live parts. Do not probe into openings or attempt to
defeat safety mechanisms .
HOT SURFA CE
The surface of the detector body may be hot while in oper ation (possibly in excess of 250°C). Caution should be
observed.
A TTENTION
Refer to the manual.
PROTECTIVE EAR TH
This internal connection provides protection against electric
shock from mains voltages and should not be remov ed.
Components of the Detector System
Components of the detector systems are listed in the tables below. Chec k
the package contents to verify that e v erything is present. Contact the
factory if anything is missing or damaged. (NOTE: damaged shipments
must remain with the original packaging for freight company inspection.)
Table 1:
Components of the D-4-I-TQ-R system (Trace GC)
Description Quantity Product number
Detector cell, PDHID 1 PD-D4-I-TQI
Pulse supply module 1 PD-M2
Instruction manual 1 MAN-PDD4-TQ
ThermoFinnigan fittings kit 1 PD-KIT-TQ
Includes
Helium purifier 1 HP2
: 1/32" polyimide ferrule 5 ZF.5V
1/16" gold-plated ferrule 5 ZF1GP
Valco to TQ adapter 1 I-23913
0.25 - 0.44 mm polyimide column ferrule 5 FS.4
0.4 - 0.5 mm polyimide column ferrule 5 FS.5
1/16" bulkhead union 2 ZBU1
1/16" tee 1 ZT1
1/8" to 1/16" reducing union 2 EZRU21
1/8" external to 1/16" internal reducer 1 EZR21
1/32" external nut 1 EN.5KN
Fused silica adapter (installed) 1 IZERA1.5
Packed column adapter 1 I-23642-TQ
Restrictor, 30 cc/min @ 60 psi He 1 TGA-R-30F60P
Introduction
3
Table 3:
Components of the D-4-I-TQI-R system (Mega and 8000 Top GC)
Description Quantity Product number
Detector cell, PDHID 1 PD-D4-I-TQI
Pulse supply module 1 PD-M2
Instruction manual 1 MAN-PDD4-TQ
ThermoFinnigan fittings kit 1 PD-KIT-TQI
Includes
Helium purifier 1 HP2
Pulser power supply 1 I-23569-1
Power cord 1 I-W-17850
Description Quantity Product number
Mounting base nut 1 35001120
Electrometer 1 23468510
Silver seal 1 29015058
: 1/16" gold-plated ferrule 5 ZF1GP
1/16" bulkhead union 2 ZBU1
1/16" tee 1 ZT1
Restrictor, 30 cc/min @ 60 psi He 1 TGA-R-30F60P
Table 3:
Components not supplied by Valco (may be obtained from ThermoFinnigan)
Introduction
4
System Requirements
Components Not Included with the Detector System
•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
•SS tubing to go from gas supply to GC
•Flow measuring device
System Purity
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 off er research g rade 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 v apor and fixed gas impurities; hence a
helium purifier is included as part of the detector system.
must alwa ys flow through the helium purifier .
The discharge gas
Whenever a ne w batch of discharge gas is receiv ed, 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 on the next page.
T ubing
Standards of cleanliness that are suitable for many GC applications may
be totally inadequate for the sensitive PDHID/PDPID work. All surfaces that
contact the gas stream must be fused silica 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” g rade regulators with stainless steel
diaphragms. Regulators with diaphragms made of neoprene or other
elastomers should never be used.
Gas Specifications
Introduction
5
edoMrotceteD
DIHDPDIPDP-rADIPDP-rKDIPDP-eX
sagegrahcsiD
sagreirraC
Any gas including He which has an ionization potential greater than 12 eV
**
Any gas including He which has an ionization potential greater than 11 eV
**
muileHeHnirA%2eHnirK%5.1eHnieX%8.0
muileH*****
Purity Specifications
•Helium (discharge and carrier gas) must have a minimum purity of
99.999%, with < 20 ppm Ne impurity . For tr ace analysis of fix ed gases,
we strongly recomment 99.9999% purity He with < 0.5 ppm Ne.
•Ar-PDPID mode: 2% ± 0.2% Ar in 99.999% He balance
•Kr-PDPID mode: 1.5% ± 0.1% Kr in 99.999% He balance
•Xe-PDPID mode: 0.8% ± 0.2% Xe in 99.999% He balance
6
Installation
General Precautions
•Do not use plastic/polymer or copper tubes for gas handling and
interconnectons. Use only stainless steel tubing with V alco 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 the discharge power switch 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.
Mounting the Detector on the GC
1. Remove the FID flame tip .
2. Install the PDD on the FID heater block. Make sure you interpose the
silver seal.
3. Tighten the nut to secure the detector.
Pulser Module Installation
1. Mount the pulser module on the GC as shown below.
2. Connect +24VDC power to the pulser module from the GC .
TO PNEUMATIC
MODULE
BIAS
GAS
INLET
ELECTROMETER
DETECTOR
MOUNTING NUT
p
u
ls
e
d
d
is
c
h
a
r
g
e
m
o
d
u
le
PULSED DISCHARGE
MODULE
D
R
A
C
D
D
P
PDD CONTROL
CARD
Figure 3: Mounting the detector on the GC
Gas Connections
Remember these three points discussed earlier: (1) all surfaces that contact
the gas stream must be fused silica or stainless steel; (2) do not use copper
tubing or brass fittings; and (3) all tubes m ust be thoroughly cleaned and
baked before use . The installation instructions below assume that the
detector discharge gas will be supplied from a nearby cylinder of helium
of the proper purity . If your installation is diff erent, y ou may need to modify
the instructions appropriately . A number of Valco fittings hav e been supplied
in the fittings kit to handle different situations.
Figure 4 illustrates gas connections for the D-4-I-TQ-R detector system.
Since the distance from the helium supply to the GC varies from installation
to installation, we do not supply tubing for that purpose.
VENT
COLUMN
INLET
TGA-R-30F60P
RESTRICTOR
(30 mL/min minimum)
DISCHARGE GAS
INLET
SAMPLE IN
(or blank)
EPC
HPM
TEE
(ZT1)
HELIUM
PURIFIER
ELECTRONIC
PNEUMATIC
CONTROL
VICI
MINIATURE
HELIUM
PURIFER
(recommended)
VENT
Installation
DISCHARGE GAS
(99.999% He)
7
COLUMN
GAS CHROMATOGRAPH
Figure 4: Gas connections for a D-4-I-TQ-R 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 finger-tight, but do not tighten the n ut 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
4. Adjust the tightness of the regulator connecting nut to allow a pressure
reduction of ~690 kPa/sec (100 psi/sec). With a ne w 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 quic kly 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.
slightly
and quickly close it again.
Installation
8
7. Open the cylinder valve to pressurize the regulator once again. Close the
valve and observe the needle of the high pressure gauge f or 15 minutes.
If it doesn’t move, there is no critical leak on the high pressure side of the
regulator.
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"
the Valco 1/8" e xternal to 1/16" internal reducer (EZR21); if it has a
1/4"
male
cone-type outlet port, install the V alco 1/4" e xternal to 1/16"
internal reducer (EZR41). For other regulator outlet fittings , a wide
variety of Valco adapters is available.
2. Remove the cap from the inlet tube of the V alco 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 remov e 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 f or 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 mo v e 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 availab le, tighten all the fittings (including the output
pressure guage), and repressurize the system for another test.
male
cone-type outlet port, install
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.
Connecting the Discharge Gas to the Detector
1. If you are supplying the GC from the helium purifier, use the Valco
ZT1 tee. 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-30F60P).
2. Connect the outlet end of the restrictor to a flow measuring device. Adjust
the helium pressure to 60 psi to obtain a continuous flow of ~30 mL/min.
3. After setting the flow rate, connect the outlet of the restrictor to the
discharge gas inlet tube (labelled “INLET”) which comes out the side
of the detector.
Detector Electrical Connections
CAUTION: Do not use a wrench to tighten the SMC
connectors on the bias and electrometer cables.
Connections should be finger tight only .
1. Referring to Figure 5 as necessary, connect the BIAS cable to the top
electrode and the electrometer cable (ELECT) to the bottom electrode.
2. Connect the high-voltage cable from the detector to the pulse supply.
Installation
9
BIAS CABLE
PULSER
MODULE
ELECTROMETER CABLE
ELECTROMETER
BOARD
Figure 5: Schematic of electrical connections
Installation
10
Initial Power-Up
CAUTION: Always make sure that dischar ge gas is
flowing before heating and powering up the detector.
1. Before installing the column, set the gas flow to 30 ml/min (measured at
the detector vent). Let it flo w f or 15 min utes so that all air is purged from
the helium purifiers.
2. Plug in the helium purifiers and turn on the GC.
3. Set the detector temperature to 100°C and allow time for the detector and
helium purifiers to reach the set temperature.
4. Plug 24 VDC into the pulser module (PD-M2).
5. Turn on the discharge.
CAUTION: During normal operation, the detector produces ultraviolet energy (UVA, UVB), some of which may
be emitted. Do not watch the ar c without ey e protection.
6. Check the standing/background current, and record it in the Detector
Perf ormance Log on the last page of this manual. Optimum range is
1.0 to 2.5 nA at 100°C. Low er current indicates a clean, leak-free system.
7. 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.
8. Install the column as illustrated on page 11, leaving the oven at ambient
temperature. Start carrier flow, then read and record the standing current.
The difference between this reading and the one pre vious 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 e xiting the column.
9. Set the column oven to the temperature required f or the intended
analysis. When the ov en reaches the set temperature, read and record
the standing current.
The difference with 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 , b ut
are still suitable for this detector. How e ver, the lo wer the b leed, the lo w er
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.
14.5 cm/
Capillary Column Connection
If the capillary column adapter is installed in the column inlet:
1. Make a mark on the column 14.5 cm from the end.
COLUMN
INLET
CAPILLARY
COLUMN
ADAPTER
(IZERA1.5)
COLUMN
FERRULE
NUT
CAPILLARY
COLUMN
2. Remove the knurled nut and plug from the capillary column adapter in the
column inlet at the bottom of the detector. Slide the nut ov er the end of
the column, followed b y the appropriate column ferrule (FS.4 or FS .5, or
ZF.5V for megabore).
3. Seat the ferrule in the detail of the column adapter and begin sliding the
column through the capillary column adapter and into the column inlet.
4. Get the nut started on the threads and tighten it until you feel it contact
the ferrule, then back off half a turn. Slide the column into the column
inlet until the mark is flush with the surface of the knurled nut, and secure
the column in the adapter by tightening the knurled nut
If the capillary column adapter has been removed, reinstall it:
1. Unscrew the liner as far as it will go, then screw the fitting body into the
column inlet fingertight.
Installation
finger tight only
11
.
13 cm/
2. While using a 1/8" wrench to prevent rotation of the liner (the part with the
seat for the column ferrule), use a 1/4" wrench to tighten the body of the
adapter until the ferrule has sealed. The liner
3. Proceed to Step 1 above.
Packed Column Connection
T o pre vent detector contamination, we strongly
recommend disconnecting the column from the
detector during column bakeout procedures.
COLUMN
INLET
The D4 is optimized for pack ed columns . The column tubing must be
thoroughly cleaned and baked before the column is pac ked. 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,
PACKED
COLUMN
ADAPTER
(I-23642-TQ)
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 sev er al hours at the
recommended bakeout temperature.
1. Loosen and remove the knurled nut and plug of the capillary column
adapter, (or remov e the column ferrule and the column if one has been
installed).
will deform
if it rotates.
PACKED
COLUMN
2. Use a 1/8" wrench to hold the liner – that part of the adapter in which the
column ferrule sits. While the 1/8" wrench k eeps the liner from rotating,
use a 1/4" wrench on the fitting body to loosen the adapter 1/2 turn.
Installation
12
3. Set aside the 1/8" wrench and completely remove the adapter from the
column inlet.
4. Screw the packed column adapter into the column inlet b y hand.
caution
with a 1/4" wrench, using an additional wrench on the flats of the column
inlet to support the detector.
5. Connect the 1/8" column to the packed column adapter with the EZR U21
reducing union supplied in the fittings kit.
, as the tip of the adapter is very fragile. Then tighten the adapter
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 tube and pressurize the entire system with helium to 138 kPa
(20 psi).
2. If the system does not hold pressure, check all the fittings with an
electronic helium leak detector.
3. Tighten fittings as required.
Exercise
CAUTION: Never use leak detecting fluids on any part
of this system.
An alternative leak testing method is descibed on page 16. NOTE: A leak
upstream from the column will not cause an immediate baseline change.
There must be time allowed for the h ydrogen to pass through the column.
Mode Selection and Setup
Helium Ionization Mode
If the instructions at the top of page 11 were properly executed, the column
should already be properly positioned. Since there ma y be some v ariation
in the flow rate f or the diff erent types of capillary columns, the user ma y w ant
to optimize the column position within ± 2.0 mm. DO NOT insert the column
more than 15 cm.
With this flow configuration, only pure helium passes through the discharge
region, minimizing the chance of discharge electrode contamination through
contact with the eluting sample. How e ver, if v ery high concentrations of
organic compounds are introduced for extended periods of time, the y could
diffuse into the discharge region and contaminate the electrodes. Under
normal chromatographic use with capillary columns, such contamination is
negligible even o v er extended periods.
Selective Photoionization Mode
13
Since the pulsed discharge detector is essentially a windowless helium
photoionization detector, changing the discharge gas from pure helium
to helium doped with argon, krypton, or xenon changes the discharge
emission profile. This results in a change in the photon energy due to
additional resonance atomic emissions and diatomic emissions from the
rare gas added. Thus a single detector can be operated in any of the
three photoionization detector (PID) modes: Ar-, Kr-, or Xe-PID.
Doped helium is used rather than other pure gases in order to retain the
benefits of the helium: namely, its transparency for Ar, Kr, an Xe resonance
radiation and its efficient cooling of the electrodes. An y prob lems associated
with the presence of a window between the photon source and the ionization
chamber are eliminated. In most applications in v olving current commercial
PIDs, analyte condensation and decomposition on the window attenuate the
lamp energy , necessitating frequent cleaning and recalibr ation.
Custom gas blends for the pulsed discharge detector are a v ailab le from
leading gas suppliers at special prices. Alternatively, they may be formulated on the spot by using appropriate fixed restrictors to mix appropriate
amounts of pure helium and pure dopant through a tee. Since all gas
streams must pass through a Valco purifier, the second option requires
an additional purifier for each dopant. This may still be more cost eff ectiv e
than requesting a custom blend of the more expensiv e Kr or Xe; since the
typical flow rate required for the pure dopant rare gas is about 0 . 3 - 1 mL/min,
a small lecture bottle can last for a long time. In either case, the total discharge gas flow rate should be the same as specified in “Gas Connections”
on page 7.
Mode Selection and Setup
14
Ar-PDPID
Changing the discharge gas from helium to a mixture of 2% argon in
helium changes the photon energy level from the 17 - 13.5 eV r ange to the
11.8 - 9.8 eV range. The argon emission consists of resonance radiation
at 11.8 eV and 11.6 eV and the diatomic Ar2 emission in the range of
9.2 - 10.3 eV. Except for fix ed gases and a f ew organic compounds like
CH4 (IP = 12.5 eV), CH3CN (IP = 12.2 eV) and some fluro-chloro hydrocarbons, the majority of organic compounds have ionization potentials
lower than 11.8 eV. Thus the Ar-PDPID is nearly univ ersal, lik e the flame
ionization detector, b ut without the risks associated with the presence of
an open flame and hydrogen.
Kr-PDPID
The recommended proportion is 1.4% Kr in He as the discharge gas.
The krypton emission consists principally of resonance lines at 10.6 eV
and 10.1 eV. The Kr-PDPID can detect compounds with IP < 10.6 eV,
which includes unsaturated and cyclic hydrocarbons, alcohols, aldeh ydes ,
organic acids, esters, etc.
Xe-PDPID
The recommended proportion is 0.8% Xe in He as the discharge gas. The
xenon emission consists principally of resonance lines at 9.6 eV and 8.4 eV,
and can detect compounds with IP < 9.6, like aromatics, ethers, alcohols ,
aldehydes, etc.
In addition to the specific compounds named in the three paragraphs
above, certain important inorganic compounds like ammonia, hydrogen
peroxide, arsenic trichloride, hydrogen sulfide , arsine, phosphine , nitric
oxide, carbon disulfide etc. can be selectively detected using the
appropriate photoionization mode.
Each dopant gas requires an additional helium purifier, which must be
purged and conditioned in the same manner as the purifier installed on
the discharge gas supply. If y ou are using more than one dopant, we
recommend use of a Valco multiposition stream selection valve so that no
fittings have to be disconnected. Not only is this convenient, it keeps the
system closed, minimizing chances of contamination. When changing from
one dopant to another, allo w at least one hour f or the old gas to be purged
from the system.
Troubleshooting
High Background Current
Disconnect the column
Pink
Check
discharge
color
Purple/
blue
Low Sensitivity
Check background current
with column removed and
column inlet plugged
High background current
(> 2 nA)
Refer to “Troubleshooting:
High Background Current”
and cap the column inlet
Do a hydrogen leak test
(described on next page)
Normal background current
£ 2 nA)
(
Reinstall column and check
background current
Background current
increases
Background current
remains in normal range
Baseline current falls to
normal range (< 2.0 nA)
Baseline current is still high
(> 2.0 nA)
Leaks in the fittings of the
PDD plumbing
Leaks inside the detector
cell itself
No detectable leaks.
The detector isn’t leaking.
Check for column bleed
and/or leaks in the GC setup.
Tighten leaking fittings
Consult
Valco
Possible bad carrier gas or
empty He bottle. Install a new
bottle.
Check column inlet for
leaks. Tighten fittings.
Check column position
according to drawing on
p. 11, and run a sample.
Baseline current falls to
normal range (< 2.0 nA)
Baseline current is still high
(> 2.0 nA)
Baseline current falls to
normal range (< 2.0 nA)
Baseline current is still high
(> 2.0 nA)
Baseline current falls to
normal range (< 2.0 nA)
Baseline current is still high
(> 2.0 nA)
Background current
remains high
Background current
drops to normal range
Sensitivity is in
acceptable range
Sensitivity is still
too low
Consult
Consult
Consult
Remove column and
condition it, then run
a sample
Run
a sample
Remove column and
bake detector at
300°C for four hours.
Install column and run
a sample.
Valco
Valco
Valco
15
Sensitivity is in
acceptable range
Sensitivity is still
too low
Sensitivity is in
acceptable range
Sensitivity is still
too low
Sensitivity is in
acceptable range
Sensitivity is still
too low
No Peaks
If the background current is stable but there are no peaks:
1. Check column flow .
2. Check the column insertion position (14.5 cm for capillary columns,
3. If there are still no peaks, check to make sure that the GC is actually making
4. If there are still no peaks, consult Valco.
13.0 cm for pack ed columns).
an injection.
Consult
Valco
Troubleshooting
16
High Noise Level
If the noise lievel is high:
1. See if it improves with the GC f an turned off .
2. Check the column insertion position (14.5 cm for capillary columns,
13.0 cm for pack ed columns.)
3. If the noise level is still high, do a hydrogen leak test, described below .
4. If there are no leaks found, or leaks are found and repaired and the noise
level is still high, consult Valco.
Performing a Hydrogen Leak Test
A hydrogen leak test allows you to pinpoint loose fittings and leaks inside
the detector.
1. Connect a length of plastic tubing to a regulated hydrogen bottle.
Establish a flow of 5-10 ml/min.
2. Hold the hydrogen outlet tube at a fitting connection for ten seconds while
monitoring the baseline.
3. Tighten the fitting and test it again, repeating as necessary until every
connection has passed the ten second test.
4. If the current remains high, hold the hydrogen outlet close to the detector .
(Do not insert the tube into any detector holes.)
indicated, contact Valco.
NOTE: This method may also be used to test for leaks in other parts of the
system, but remember – a leak upstream from the column will not cause an
immediate baseline change. There m ust be time allow ed f or the h ydrogen to
pass through the column.
If a leak in the detector is
Warranty
17
This Limited W arranty giv es the Buy er specific legal rights, and a Buy er
may also hav e 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, the y
will be delivered prepaid and Seller will bear all risks of loss until delivery to
Buyer. Buyer and Seller ag ree 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 W arranty 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.
18
Detector Performance Log
In addition to the occasions indicated in the Comments area of the table below (see
Initial Pow er-Up
page 10), 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 do wnloaded from the support/manuals section of www.vici.com.
Detector Model: Serial Number: Date of purchase:
Date
Operator Column
D-4-I-TQ-R
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)
,
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