1. S Compounds by
Hyphenated GC/PIDFPD
John N. Driscoll & Jennifer Maclachlan
PID Analyzers, LLC
Sandwich. MA 02563
Presented at the ACS Fall Nat. Meeting
Indianapolis, IN Sept. 2013
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2. Introduction
• The S compounds of interest in the atmosphere include
H2S, DMS, COS, SO2,and CS2.
• We were interested in determining the detection limits,
reproducibility, linearity of the Flame Photometric
Detector (FPD) for S compounds
• We wanted to use a photoionization detector (PID) with
an FPD in series to improve the response and detection
limits
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3. Methods for S Cpds
• EPA- Gas Chromatography/Flame Photometric Detector
• For stack (with a dilution system) or ambient air analysis
• EPA DL- app. 100 ppb
• BA APCD DL- 500 ppb
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4. Using the PID In combination with a S
Selective Detector (FPD)
• PID/FPD- The PID is nearly 100x more sensitive for H2S
and CH3SH, than the FPD, the dynamic range is > 107 and
it provides additional confirmation that no HC are present
• A ratio of the response factor PID/FPD will confirm that
only a S compound is present since the PID responds to
both S & HC
• Response of the PID is linear with concentration while the
FPD (S) is sq rt. with concentration
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5. FPD & PID for Sulfur Compounds
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6. FPD Schematic
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7. Photo of PID Analyzers GC 301 C
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8. Abundance of S Compounds in the
Atmosphere + DL FPD & PID
ppb S in
S
the
Compound Atmosphe FPD
PID DL
re
D L ppb Need Conc. ppb
Dimethyl Sulfide
40-110
Sulfur Dioxide
160+/-100
Hydrogen
Sulfide
121-829
Carbon Disulfide
37 +/- 10
Carbonyl Sulfide
509+/- 63
IP (eV)
100
Y
1
100
Y
NR
8.43
12.5
100
N
10
10.46
20
N
2
10.07
50
N
NR
11.18
Source S levels: Chemistry of the Natural
Atmosphere, Peter Warneck, Academic Press,
NY (1988)
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9. Lifetime of Sulfur Compounds in the Lower
Atmosphere
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Rate Coefficients ( !0-12 cm3/molecule s)
Compound
OH Rate*
O rate*
Lifetime in
Troposphere
Days
H2S
5.0, 5.6
0.027
4.4
CH3SH
90, 130
1.9
0.3
DMS
9.1, 45
63, 48
0.6
DMDS
223
CS2
0.43, 2.0
COS
0.1
5.5
>0.04
Source: Chemistry of the Natural Atmosphere,
Peter Warneck, Academic Press, NY (1988)
12
44 yrs
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10. Properties of Sulfur Compounds
S Cpd.
BP deg C
PEL ppm
H2S
-60
10
COS
-50.3
SO2
-10
2
DMS
37.5
10
CS2
46.3
20
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11. GC/FPD of Reduced S on thick film capillary + packed
columns
Packed column chromatography- Anal. Chem.
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12. Sensitivity PID/FPD
Chromatograms of PID & FPD overlapped
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13. Extended Range of PID
The PID extends the range
of the FPD and the latter
detector confirms the
presence of S
Note: Quenching of FPD at higher
H2S levels reduces sensitivity
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14. Comparison of Exponential vs
Linear Fit
4 point Calibration linear fit
Exponential Fit Response
H2S by FPD
1.4
H2S CA L I BR ATI ON CUR V E FOR FPD
1.2
1.4
4 point cal for linearizaton
1.2
y = 0.151e0.084x
1
Improves linearity
PH 000
1
0.8
0.6
0.8
0.6
0.4
0.4
0.2
0.2
0
0
0
5
10
15
20
25
30
0
5
10
15
20
25
30
ppm H2S
PPM H2S
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15. Reproducibility of H2S via GC/PID-FPD
PID ppm
0.872
0.9425
0.923
1.0728
0.911
0.9703
0.999
1.0173
1
0.8951
1.014
0.9642
0.933
1.0634
1.007
0.9541
0.883
Ave
Std Dev
CV %
FPD ppm
1.0864
1.017
0.95
0.055
5.78
1.0325
1
0.064
6.39
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16. Summary
• Lighting an FPD is frequently an issue but our
piezoelectric igniter simplifies this issue
• 4 point calibration in SW improves the linearity of the
FPD for S and eliminates the square root response
• The PID extends the range of the FPD and the latter
detector confirms the presence of S
• The reproducibility of both detectors at high ppb levels
is similar but the 4 point calibration improved the FPD
precision
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