Abstract
The determination of dimethylsulfoxide (DMSO) at the nanogram level in aqueous solutions is described. After removal of dissolved volatile sulfur compounds by sparging with helium, DMSO is reduced to dimethylsulfide with sodium borohydride or chromium(II) chloride. The dimethylsulfide is stripped from the solution with a stream of helium and trapped on a chromatographic packing in a U-tube immersed in liquid nitrogen. After gas chromatographic separation from potentially interfering compounds, the dimethylsulfide is measured by a flame photometric sulfur detector and/or a flame ionization detector. The detection limit of the method is 1 ng S(DMSO) per sample, which corresponds to 0.02 micrograms S(DMSO)/liter. Precision is 5-10%, depending which variant of the method is used. The method has been used for the determination of DMSO in a variety of samples, including seawater, freshwater, rain, and phytoplankton culture solutions. DMSO appears to be a common constituent in natural waters. Its occurrence in seawater is restricted to the zone of light penetration. It may occur as an end product of algal metabolism. The occurrence of DMSO in rain may be due either to the release of this substance from the biosphere into the atmosphere or to the atmospheric oxidation of DMS to DMSO. (Baker-FRC)