detection of low ppb levels of chlorinated hc by gc-pid (11.7)a
Post on 18-Apr-2015
48 Views
Preview:
TRANSCRIPT
Dr. John Driscoll PID Analyzers, LLC
2 Washington Circle Sandwich, MA 02563
Paper #2340-14 Booth # 2080
1
Detection of Low ppb Levels of Chlorinated HC by GC-PID (11.7)
A number of GC detectors have been used for the analysis of chlorinated hvdrocarbons (Cl HC) in environmental samples. Man have been found unsatisfactory
The problems have included: complexity, low response factors, poor detection limits, significant variation with the degree of unsaturation, limited selectivity…
The PID does not solve all of the above problems but it is easy to use, has ppb detection limits and the response does not vary widely with structure
2
Detectors for Cl HC have depended upon the following principals:
A. electron absorbing properties- ECD B. decomposition in furnace & detection of H+-
ElCD C. thermionic emission in a flame- Cl-
D. photoionization detection (PID) with a 10.2/10.6 lamp
Each of these detectors have their limitations In this paper, we will discuss the use of a PID
with an 11.7 eV lamp that will solve some of the previous detector limitations
3
Detector Det Limit Limitation
ECD low pg
structure, licensing, operation , easy to saturate
ElCD low ppm conc, furnace, concentrator is required for ppb levels
Alkali Flame mid ppm conc, reliability, specificity
PID 10.6 low pg specificity
4
5
6
7
8
9
Name IP eV 10.6eV Response 11.7 eV Response
Chloroform 11.42 0 3.15
Carbon tetrachloride 11.47 0 4.22
Chloroethanol 0.20 6.70
Methylene chloride 11.35 0.14 6.83
Methyl chloride 11.28 0 7.60
Vinyl chloride 10.00 3.20 7.80
1, 1, 2, 2-tetrachloroethane 11.10 0 8.60
Dichloromethane 11.35 0 8.70
Ethyl chloride 0 9.20
Epichlorohydrin 10.60 0.70 10.30
Ethylene dichloride 11.00 0 10.50
1, 1, 1-trichloroethane 11.25 0 10.70
Allyl chloride 10.20 1.30 11.90
1, 3-dichloropropane 10.85 0.20 12.10
1, 2-dichloropropane 10.87 0.20 12.10
o-dichlorobenzene 9.07 11.90 15.50
m-dichlorobenzene 9.12 11.90 15.50 10
11
12
y = 6.0204x + 2100.5
0
50000
100000
150000
200000
250000
300000
350000
0 10000 20000 30000 40000 50000 60000
PH fo
r 11.
7 PI
D
ppb CHCl3
13
SENSITIVITY wo PRECONCENTRATION PID 10.6 eV- need unsaturation- low ppb
detection PID 11.7 eV sub ppm detection ECD-needs multiple Cl to achieve low level
detection- MeCl2 example ElCD PPM- need oven to decompose- low
ppm min det. Requires concentrator for ppb
14
# of Cl ECD PID 11.7
1 5 62
2 30 65
3 100 70
4 600 80
5 5000 85
6 40000 100
15
y = 0.2678e1.956x
y = 7.5x + 48.333
0
1000
2000
3000
4000
5000
6000
0 2 4 6
Series1
Series2
Expon. (Series1)
Linear (Series2)
chlorobenzenes
Name Conc ppb
Height % Area % Time
1 TCE 500 973374 40.29 312042784 43.14 1:04
2 PCE 500 746159 30.88 228910192 31.65 1:34
3 TCB 500 664208 27.49 173209056 23.95 2:07
16
-200000
0
200000
400000
600000
800000
1000000
1200000
0:00 1:40 3:20 5:00 6:40 8:20 10:00min
1
23
4
The 11.7 PID is very useful for low MW HC such as CHCl3, CCl4, CH2Cl2, CH3Cl etc. Detection limits for CHCl3 were found to be 50 ppb for 0.5 cc sample
For the chlorinated HC with double bonds the PID with a 10.6 eV lamp, the detection limit is 1-2 ppb
The PID is one of the most sensitive detectors for Cl HC and a wide range of compounds can be detected with the 10.6 & 11.7 eV lamps
17
top related