A Purge and Trap Gas Chromatographic Method for Dimethyl Sulfide in Freshwater

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Abstract
A simple purge and trap method is described for extracting trace levels (ng. 1−1) of dimethyl sulfide (DMS) in freshwater samples. The DMS extracted is determined in a gas chromatograph equipped with a dual-flame photometric detector and a 2-m Chromosil 330 Teflon column. Good recoveries (93-105%) are achieved when diethyl sulfide is used as an internal standard. The standard error of the mean (for replicates) is about 5% at low (8–10ng. 1l−1) DMS concentrations and about 3% at higher (90–130ng. 1−1) concentrations. The detection limit for the method is about 0.8ng. 1−1DMS. Water samples containing DMS should not be stored even at low temperature for more than 6 hours, but once extracted, the DMS may be preserved in the gas sample vials for weeks. The method has been used in determining the natural levels of DMS in surface waters from Hamilton Harbour (Lake Ontario). The values found between April and July, 1986 typically varied from 40 to 770ng. 1−1, and were much lower then the levels generally observed in the oceans.