Direct analysis and monitoring of organosulphur compounds in the gaseous phase using portable mass spectrometry

Organosulphides are ubiquitous in the natural world and are important in the agriculture, pharmaceuticals and petrochemical sectors. For the first time a lightweight (12 kg), man-portable membrane inlet mass spectrometer (MIMS) has been employed to analyse volatile organosulphur compounds (VOSCs) in the gaseous phase. Monitoring of such compounds in field conditions (outside the chemical laboratory) is of great importance for environmental reasons. Representative compounds tested include: 2-methyl-2-propanethiol, 1-propanethiol, diethyl disulphide, 1-butanethiol, ethanethiol, thiophene, methyl ethyl sulphide and dimethyl disulphide. Experiments in the gas phase were performed at low parts-per-billion (ppb) analyte levels. The results obtained showed low limits of detection (high parts-per-trillion – ppt), very good linear regression within the examined concentration range, fast membrane response times and good repeatability with relative standard deviation, RSD < 4%. Analysis of a complex multi-component gaseous mixture of organosulphur compounds was also demonstrated.