| 英文摘要 |
The main objective of this project is to develop sampling and analytical method for selected organic air pollutants (i.e., 1,4-dioxane, 1,3-butadiene, vinyl acetate, acetonitrile, benzyl chloride, 1,2-dibromoethane, bromomethane, chloromethane, 1,1-dichloroethylene, 1,1,2-trichloroethane, allyl chloride and 1,4-dichlorobenzene) in flue gas from stacks and provide testing methods for the Environmental Analysis Laboratory, EPA. In the early stage, we planned to analyze all the target organic air pollutants by combining sampling bags and gas chromatography - flame ionization detection (GC-FID). However, due to the large difference in boiling points from -24~179°C and volatility (vapor pressure from 3796 ~1.03 mmHg), as well as the co-existence in different phases of gas, mist or particulate matter in flue gas, we had to divide the target compouds into three separate groups with more tailored methods for each. For the first group of 8 compounds (benzyl chloride, 1,2-dibromoethane, bromomethane, chloromethane, 1,1-dichloroethylene, 1,1,2-trichloroethane, allyl chloride and 1,4-dichlorobenzene ether), they were analyzed by combining sampling bags and GC-electron capture detection (GC-ECD) for analysis. 1,3-butadiene and vinyl acetate formed a second group and were analysis by sampling bags and GC-FID analysis. The third group of highly dissolvable compounds of 1,4-dioxane and acetonitrile were sampled by impingers, followed by GC-FID analysis
To test for linearity and construct calibration curves, we further divided the 12 target compounds into two concentration ranges of low and high. For the high range from 0.67 ~ 10 ppm, the R2 = 0.993~0.999, whereas for the low range from 3~50 ppm, the R2 = 0.997~0.999, both ranges showing very high linearity. The detection limits of the 12 target analytes are in the range 0.0128~0.527 ppm. The sample preservation test showed that for the 10 analytes using sampling bags except for 1,4-dioxane, which has a very short preservation time period no longer than 4 hours, the other 9 analytes showed much longer preservation time of 1~2 days. 1,4-dioxane and acetonitrile are water soluble and thus can be preserved in water after impinge sampling with a preservation time period longer than 9 days. The precision for the 12 target analytes are in the range1.5~10.9%. The recoveries are in the range 96.6~106.1%, demonstrating high accuracy.
Having determined the suitability of the three analytical methods, criteria of quality assurance for the methods were then assessed, which include accuracy, detection limits, precision and linearity.
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