Abstract A method of determination of organic compounds by headspace gas chromatography after sorption on solid sorbents and liquid desorption has been developed. Water (50%) is added to dimethyl sulphoxide after completion of desorption, which results in an increase of up to two orders of magnitude in the concentration of compounds in the gaseous phase. Owing to its increased sensitivity, the method can be employed for the determination of compounds in the sub-ppb★ range from small volumes of air or water. An apparatus enabling simultaneous analysis of several samples containing compounds with high and low boiling points without the loss of the latter, and multiple extraction of the sorbent bed, is described. Average recoveries of model compounds [(CH 3) 2S, (CH 3) 2S 2, (C 2H 5) 2S 2] are close to 100%, indicating the high accuracy of the method. The calibration curves were linear over the studied range of concentrations. The overall precision, expressed as the relative pooled standard deviation, varied from 2.4% [(CH 3) 2S] to 5.2% [(C 2H 5) 2S 2] for samples and from 2.5% [(CH 3) 2S] to 9.1% [(C 2H 5) 2S 2] for standards. The detection limit was estimated to be 0.17, 0.77 and 0.76 ppb for (CH 3) 2S, (CH 3) 2S 2 and (C 2H 5) 2S 2, respectively, assuming a 1-dm 3 liquid sample.