This document discusses using a gas chromatography system with a thermal conductivity detector (TCD) and far-ultraviolet (FUV) detector to monitor air quality in Chinese coal mines. A combination of a molecular sieve 5A column and HSQ column is used to separate gases like O2, N2, CH4, CO, NO, NO2, and SO2. The TCD detects high concentration gases over 500 ppm, while the more sensitive FUV detects low ppm levels of contaminants. Using the detectors in series provides a wide dynamic range of 10 million for analysis of coal mine air samples.

1. Dr. Jack Driscoll, PID Analyzers, LLC
Paper #270-17P
Sunday, Feb. 28, 2010
Pittcburg Conf. on Anal. Chem.
Orlando, FL Feb. 28, 2010
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2. 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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3. Target Compounds for Coal Mines
Compound
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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4. UV photo
diode
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5. FUV Detector Schematic
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7. FUV Sensitivity vs Absorption Coefficient
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8. 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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9. FUV Range
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10. Calibration Curve for Methane
600
ppm CH4 Peak Ht
Thousands
y = 21.831x + 6121.1
R² = 0.9964
25000 539173 500
12500 302620
6250 144479 400
FUV Peak Height
3100 81241
300
1550 38061
775 19000 200
500 9800
100
388 7500
40 810
0
0 5000 10000 15000 20000 25000 30000
ppm Methane
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17. TCD Precision
O2 % 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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18. 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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19. FUV/PID
In-Series
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20. FUV/FID
In-Series
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21. 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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