Stepwise injection photometric determination of mercaptanes in air

An automated procedure is developed for the photometric determination of mercaptanes in air. To achieve the required selectivity of analyte determination, a scheme of sample preparation was elaborated, which includes the liquid absorption separation of interfering components (hydrogen sulfide and sulfur dioxide) and mercaptanes on two consequent chromatography columns with glass wool impregnated with a zinc acetate solution and an alkaline solution of cadmium chloride. Therein, the impurities specified were separated in the first column, while the target materials were gathered on the second one. The materials were detected with high sensitivity by their reaction with an iodine/starch complex under the conditions of step-wise injection analysis. The analytical range for mercaptane sulfur was from 0.5 to 7.5 μg/m³ for a sample volume of 1 m³.