Sampling and gas chromatographic analysis of volatile sulphur compounds and gases at sub-v.p.m. Levels in the presence of ozone

Abstract

A method is presented for the sampling and analysis of sulphur gases (hydrogen sulphide and methanethiol) and volatile sulphur compounds (higher thiols and organic sulphides) in both ambient air samples and air containing ozone. The method has been developed for the quantitative analysis of hydrogen sulphide and for the semi-quantitative and qualitative analysis of other sulphur compounds. Field sampling and sample storage make use of simple cryogenic techniques and the analysis is carried out using a combination of thermal desorption and cryogenic re-trapping with sulphur-specific gas chromatography. Sample volumes of 100 ml and collection times of 1 min per sample are typically used for hydrogen sulphide in the range 0.1–1.0 volume parts per million (v.p.m.) with a limit of detection estimated to be better than 70 volume parts per billion (v.p.b.). The technique has been used in connection with odour control and measurement at a sewage treatment works, and in the assessment of odour control plant effectiveness.