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Dr. Jack Driscoll, PID Analyzers, LLC Paper #270-17P Sunday, Feb. 28, 2010 Pittcburg Conf. on Anal. Chem. Orlando, FL Feb. 28, 2010 PID Analyzers, LLC copyright 2010
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Dr. Jack Driscoll, PID Analyzers, LLCPaper #270-17P
Sunday, Feb. 28, 2010Pittcburg Conf. on Anal. Chem.
Orlando, FL Feb. 28, 2010
PID Analyzers, LLC copyright 2010
Presentation Background There are more than 20,000 coal mines in China China relies heavily on the use of coal for power
generation and will be opening a new coal fired power plant every --- months to keep up with their power demands
China is in the process of closing down many of the smaller mines and focusing on the larger ones
Now the need exists to improve the monitoring of the air in coal mines
The method selected was GC with a TCD & FUV
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Target Compounds for Coal MinesCompound
O2 % TCD FUV
N2 % TCD
CH4 h- ppm TCD FUV
NO ppm FUV
CO ppm FUV
NO2 ppm FUV
SO2 ppm FUV
VOC’s ppm FUV
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UV photodiode
FUV Detector Schematic
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FUV Sensitivity vs Absorption Coefficient
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Absorption coefficients & estimated detection limits in the Far UV
Compound Abs coeff (cm-1) Det. Limit (ppm)
CO 3 300
CO2 6 140
O2 6.3 130
NO 82 10
NO2 400 2
CH4 485 2
NO2 500 2
H2S 900 1
SO2 1000 1
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FUV Range
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Calibration Curve for Methaneppm CH4 Peak Ht
25000 539173
12500 302620
6250 144479
3100 81241
1550 38061
775 19000
500 9800
388 7500
40 810
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y = 21.831x + 6121.1R² = 0.9964
0
100
200
300
400
500
600
0 5000 10000 15000 20000 25000 30000
FUV
Pea
k H
eigh
t
Thou
sand
s
ppm Methane
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PID Analyzers, LLC copyright 2010
TCD PrecisionO2 % N2 %20.29 79.55
20.99 80.7
20.83 80.39
20.69 80.24
20.55 80.15
20.86 80.48
20.58 80.1
21.06 80.41
20.88 80.54
20.61 80.23
20.54 79.97
20.64 80.24
20.75 80.24
21.26 80.4
20.4 79.54
20.6 79.92
20.83 79.42
20.77 79.5
21.08 79.72
20.35 79.25
20.84 79.51
Avg. 20.73333 80.02381
std. dev. 0.2482 0.425869
CV % 1.197107 0.532178
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FUV Precision for methane
FUV % O2
21.01
21.35
21.66
21.16
20.24
21.28
20.45
Ave 21.02143
Std dev 0.506472
CV % 2.409315
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FUV/PIDIn-Series
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FUV/FIDIn-Series
Summary The FUV/TCD in series has been evaluated for the analysis of
gases in coal mines. The TCD is used to detect high levels of gases > 500 ppm and the FUV to detect low ppm levels of contaminants such as CH4, NO, NO2, SO2…
A combination molecular sieve 5A and HSQ column in-series is used for the separation. The O2, N2, CH4 and CO are only slightly retained on the HSQ but are baseline separated on the mole sieve (MS). Once the separation is complete on the MS, the columns are backflushed and the components on the HSQ are eluted to the detector.
The use of detectors in-series for analysis of samples provides a dynamic range of approximately 10 exp 6 for the two detectors
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