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RECEIVED for review December 16,1987. Accepted April 25, 1988. Part of this paper was presented at 8th International Symposium of Capillary Chromatography, Riva del Garda, Italy, May 19-21, 1987. This work was supported by a Grant-in-Aid for Cancer Research from the Ministry of Education, Science and Culture (No. 62010037).
Determination of Reduced Sulfur Compounds in Aqueous Solutions Using Gas Chromatography Flame Photometric Detection Caroline Leck* Department of Meteorology, University of Stockholm, S-106 91 Stockholm, Sweden
Lars Erik Bagander Department of Geology, Section Microbial Geochemistry, University of Stockholm, S-106 91 Stockholm, Sweden
A method for simultaneous analysis of hydrogen wlfkle (H,S), methyl mercaptan (CH,SH), carbon disulfide (CS,), dimethyl sulfide (DMS, CH,SCH,), and dimethyl disulfide (DMDS, CH,SSCH,) In aqueous solutions is described. The reduced sulfur compounds are released from the aqueous sample (50-200 mL) by purging with N, and then trapped cryogenically in a U-shaped sample tube with llquld nitrogen. The sample tube was sealed with end caps and placed in a portable freezer. Under stable conditions In the laboratory, the sulfur compounds are released by controlled heating and Injected onto a packed column gas chromatograph with a flame photometric detector. The precision of the method for environmental samples was better than f5% for ail compounds except for H,S, for which the precision was f25%. The detection llmlts for H,S, CH,SH, CS,, DMS, and DMDS were 1, 0.6, 0.2, 0.2, and 0.4 ng-L-' S, respectively, in a 200-mL natural sample. Analyses of environmental samples have been successfully performed with the described method.
The estimated flux of 30-50 Tg of S/year of reduced sulfur compounds from the oceans ( 1 )contributes significantly to the atmospheric sulfur budget. In that flux, dimethyl sulfide (DMS) dominates (99%) over other reduced sulfur compounds (1). Due to analytical difficulties, the estimates of sea to air fluxes of carbon disulfide (CS,), methyl mercaptan (CH,SH), hydrogen sulfide (HzS) and dimethyl disulfide (DMDS) may have been systematically underestimated (2-4). These reduced sulfur compounds originate mainly from marine phytoplankton. So far, the mechanisms leading to the production of the reduced sulfur compounds in surface waters are not well understood. We have developed an analytical method where simultaneous detection of HzS, CH,SH, CS2, DMS, and DMDS can be performed in a single seawater sample. This is a great improvement compared to earlier methods (3-5) when interpreting measurements, especially when one wishes to understand the regulating mechanisms for the production
and fluxes of reduced sulfur from the oceans to the atmosphere. The analytical device consists of an easily handled field sampling system separated from the analytical system; the latter was kept under stable conditions in the laboratory. This two-step procedure allows sea surface sampling by helicopter where large areas can be covered within a short time span. A particular advantage with this sampling technique lies in the interpretion of the reduced sulfur emissions as a function of meteorological and biological parameters without considering induced variability due to long sampling times. The analytical method has been tested on more than 400 seawater samples, with total reduced sulfur concentrations ranging from
