Quantitation of volatile sulphur compounds in polluted waters

A study on the linear dynamic range of a combined cryogenic trap-gas chromatographic method with flame photometric detection (FPD) has shown that quantitation of volatile sulphur compounds (VSCs) in heavily polluted waters, in the order of hundreds of nanograms, is possible. A correct calibration of the FPD is needed for this purpose. Calibration over 2.5-3 orders of magnitude requires the determination of three different linear equations extending over this mass range. Equations for hydrogen sulphide, carbonyl sulphide, methanethiol, dimethyl sulphide and carbon disulphide are given. The intervals corresponding to each linear equation are determined from the inflexion points in the calibration plots. The changes in sign of the relative error resulting from re-calculation of the VSC mass after use of one single calibration curve for the whole mass range interval provide a secondary criterion of interest. (C) 1997 Elsevier Science B.V.