A simple method for routine measurement of organosulfur compounds in complex liquid and gaseous matrices

Abstract

The measurement of VOSCs in complex matrices is challenging due to their volatile and reactive nature. A straightforward method using headspace chromatography was developed for routine analyses of organosulfur compounds in a high saline liquid matrix with a pH of 8.4. Direct sample acidification with a 1M acetate buffer (pH 3.6) showed an increased response for methanethiol, ethanethiol, propanethiol, dimethyl sulfide, dimethyl disulfide and diethyl disulfide. A good quadratic fit (R² <0.995) was obtained for each compound over a calibration range of 5 µM-S until 125 µM-S (µmol sulfur/L). Gas standards were measured using the same chromatographic conditions over a calibration range of 0.08 µM-S until 1.85 µM-S (R² <0.999). Gas standards could also be used to calibrate the liquid phase with a response ratio of 105.2% for ET, 107% for DMS, 105.7% for PT, 108.9% for DMDS and 106% for DEDS. This alternative calibration strategy reduced the preparation time and does not rely on liquid standards, which were unstable over time. This method was used to determine Henry constants for the organosulfur compounds both in demineralized water and the high saline liquid matrix and to analyze samples from a bio electrochemical experiment that treated methanethiol. This new method allows for routine analysis of samples originating from natural gas desulfurization plants and can potentially also be used to analyze organosulfur compounds in other complex waste streams.

Keywords: Disulfide; Flame Photometric Detector (FPD); Gas chromatography (GC); Henry coefficient; Thiol; Volatile organosulfur compound (VOSC).