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TECHNIQUE FOR MEASURING REDUCED FORMS OF SULFUR IN AMBIENT AIR
Citation:
Braman, R. AND J. Ammons. TECHNIQUE FOR MEASURING REDUCED FORMS OF SULFUR IN AMBIENT AIR. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/7-81/041 (NTIS PB81179772), 1981.
Description:
A new technique for measuring low concentrations of volatile sulfur compounds in ambient air is discussed. The technique consists of preconcentration of sulfur compounds by chemisorption on gold metal coated sand or gold foil surface followed by thermal desorption, separation, and detection by flame photometry. Breakthrough capacities are on the order of 1 microgram total sulfur compounds. The unique aspect of this research is the derivation of thiol type compounds, principally H2S and CH3SH, by ethyl iodide for partial separation of H2S, DMS, SO2, COS, and CH3SH. Best suited for the 0.01-5 ppb range, the technique has been used to detect trace sulfur compound concentrations as low as 0.001 ppb by volume with 100L and larger sample volumes. Sample size detection limits depend upon the type of flame photometric detector used but are generally in the 0.1 ng range. Repeatability of measurements is + or - 5-8% relative standard deviation. Accuracy depends upon the compound. DMS and SO2 are detected as individual compounds. H2S, CS2 and COS are detected as a single compound on gold foil. Methylmercaptan and dimethyldisulfide appear as a single compound. Field studies at two sites, Cedar Island NC and Prairie View, Texas, have demonstrated that the technique is practical for field use and for determining vertical profiles up to 10 meters above ground level. Hydrogen sulfide, dimethylsulfide, sulfur dioxide and carbonylsulfide were the principal reduced forms of sulfur detected at these sites.