VICI D-4-I-TQI-R User Manual
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
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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
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