Pittcon Feb 2010: Fourth Generation PID Analyzer Improves Sensitivity

Pittcon Feb, 28, 2010, Orlando, FL

Dr. Jack Driscoll
PID Analyzers LLC
Analyzers,
Paper # 180-5
Session 180 - GC Detectors

2/1/2010 PID Analyzers, LLC Copyright 2010 www.pid.bz

 The first commercial PID was introduced at Pittcon in 1976 by
HNU Systems. This detector was found to be 50 x more sensitive
than the FID
 This detector has gone through several redesigns since then and
has found a niche in environmental and trace analysis with
more than 15,000 units sold
 A fourth generation PID has been developed that has improved
noise characteristics in the lamp circuit and in the electrometer.
The high voltage circuit employs a Cockcroft Walton multiplier
and uses a constant current source instead of a constant voltage
design that
d i th t was used previous PID’ Thi has resulted in a 20-
d i PID’s. This h lt d i 20
30% reduction in the background noise level and allowed us to
achieve sub pg detection levels for aromatic compounds.

2/1/2010 PID Analyzers, LLC Copyright 2010

1976 2010
Ion chamber: Ion h b
I chamber:
teflon ceramic/gold
Max T; 200C Max T; 275C
Dead vol: 500 uL Dead vol: 100 uL
Sensitivity: 10 pg Sensitivity: 1 pg
benzene
b benzene
Temp cont: variac Temp cont: digital
proportional

PI52 ELECTROMETER CONTROLS

 Input Att’n x1, x10
 Output Att’n x1 x10
Att n x1, x10,
x100
 Autozero
 Proportional T Control
 Lamp on/off
 LCD-Temp
LCD Temp set or
Detector output
 Fine Gain pot


Process
 R + h = R + + e-

 where


 R= molecule
 h = a photon with an
p
 energy > IP of R
 R+ = positive ion
 e- = electron


PID COMPONENTS

 LAMP
 ION CHAMBER
 HV FOR LAMP
 BIAS FOR ION
CHAMBER
 HEATER
 THERMOCOUPLE


 Linear dynamic range > 5 x107
 Detection limit <0.5 ppb benzene
 Non destructive; other detectors can be run in-series
 Sensitivity increases as the carbon number increases (carbon
counter)
 For 10.2 eV lamp, responds to carbon aliphatic compounds >
C4, all olefins and all aromatics
 The PID also responds to inorganic compounds such as H2S,
p g p ,
NH3, Br2, I2, PH3, AsH3, e.g. any compound with an ionization
potential of < 10.6 eV
 The PID is more sensitive than the FID; >200 x more sensitive
for aromatics, 80 times for olefins & 30 times for alkanes > C6
aromatics olefins,
 Non destructive detector; other detectors can be run
downstream
 Concentration sensitive detector


 p
More compact size
 Reduced lamp noise level
 Reduced electrometer noise with
improved design and IC’s
p o ed des g a d C s
 Reduced dead volume of detector
 Digital temperature control
 Optional USB ADC
 PC Control
 PeakWorks chromatography software
 Operates with a Web PC



PID 10.6 eV


BTEX with PeakWorks Chromatograph Software
Chromatography

5 ppb BTEX
b


Detector Benzene 5 ppb Benzene 50 ppb
1 CV = 9.99 % @ 4.9 ppb CV = 2.37 % @ 48.5 ppb

2 CV = 3.2 % @ 4.73 ppb CV = 1.37 %@ 47.4 ppb

3 CV = 13.7 % @ 4.7 ppb CV = 0.76 % @ 49.6 ppb

4 CV = 13.7 % @ 4.7 ppb CV = 0.69 % @ 50.3 ppb

5 CV = 18.4 % @ 5 ppb CV = 1.82 % @ 50 ppb

Avg 5 ppb =11.8 Avg 50 ppb = 1.40

Ethyl Benzene 5 ppb Ethyl Benzene 50 ppb

1 CV = 16.4 @ 5.0 ppb CV = 1.35% @ 48.5 ppb

2 CV = 5.9 @ 4.5 ppb CV = 1.7% @ 47.44 ppb

3 CV = 17.5 @ 4.37 ppb CV = 2.74% @ 49.46 ppb

4 CV = 14.5 @ 4.2 ppb CV = 3.2% @ 50.2 ppb

5 CV = 43.1 % @ 2.7 ppb CV = 3.7 % @ 47.4 ppb

Avg 5 ppb = 13.50 Avg 50 ppb = 2.44

Note: Each set of data is 5 runs


 Photoionization Detector
 1st commercial introduction in 1976 by
HNU (Driscoll)- 50x more sensitive than
FID for aromatics low ppb
aromatics-
 Far UV Absorbance Detector
 1st commercial introduction in 1985 by
HNU (Driscoll)-low ppm sensitivity-
nearly universal response
 Flame Ionization Detector
 1st commercial introduction in late 1950s-
(ICI ) hydrocarbons- sub ppm
y


Detectors and Characteristics
PID FUV FID
Species
C1-C4 alkanes
C1- N Y Y
C5+ alkanes Y Y Y
Alkenes Y Y Y
Aromatics Y Y Y
Dynamic Range 5 x 10exp7 1 x 10exp5 1 x 10exp6

Detection Limits
Air
aromatics < 0.5 ppb 500 ppb 50-100 ppb
50-
alkenes <5 ppb 500 ppb 50-100 ppb
50-
alkanes < 10 ppb 500 ppb 50-100 ppb
50-
Water
aromatics < 0.1 ppb 10 ppb 2.5-10 ppb
2.5-
alkenes 0.1 ppb
01 10 ppb 2.5-10 ppb
2 5-
2.5
alkanes 1 ppb 10 ppb 2.5-10 ppb
2.5-

 If a GC detector does not destroy the sample,
then a second detector can be run in-series.
The advantage is that additional confirmation
can be obtained during a single run. A
number of EPA methods specify dual
detectors for analyte confirmation. S
d t t f l t fi ti Some non-
destructive detectors are:
 PID

 FUV

 TCD


 PID- FID- identification of aromatics,
PID- FID
alkanes & alkenes as a result of the
differential response
 PID-FPD Total HC and ID of S or P
PID-FPD-
compounds in the mixture
 PID-FUV wider HC response (low MW HC
PID-FUV-
& Cl HC) and expansion of the range of
Cl-HC) d i f th f
compounds detected in low ppm
 TCD- i
TCD universal d t t ( ppm t %)- and
l detector to %) d
expansion of the range of compounds
detected in high ppm
g pp


FUV/PID 11.7
In-series


PID/FID
In parallel
ll l


 We have shown that the new 4th
generation PID
 Is the most sensitive detector for VOC’s
 Has improved sensitivity
 Is more compact and versatile
 Can be combined with other GC
detectors to improve the range of
compounds detected & help identify
unknowns


Pittcon Feb 2010: Fourth Generation PID Analyzer Improves Sensitivity

Recommended

Recommended

More Related Content

What's hot

What's hot (9)

Viewers also liked

Viewers also liked (16)

Similar to Pittcon Feb 2010: Fourth Generation PID Analyzer Improves Sensitivity

Similar to Pittcon Feb 2010: Fourth Generation PID Analyzer Improves Sensitivity (20)

Pittcon Feb 2010: Fourth Generation PID Analyzer Improves Sensitivity