The analytical method described here permits the determination of methanesulfonic acid [75-75-2] occurring as inhalable particles and vapour in workplace air. The concentration range covers one tenth up to twice the currently valid Occupational Exposure Limit Value (OELV) in Germany of 0.7 mg/m3 (inhalable fraction). The peak limit with an excursion factor of 1 for the inhalable fraction and vapour can also be checked. Sampling is performed using a flow-regulated pump to draw a defined volume of air through a quartz fibre filter, which is alkaline-impregnated with sodium carbonate and inserted in a GSP sampling system. The volumetric flow rate is 10 l/min. For sampling, 2 hours or 15 minutes can be used. Alternatively, an intake cone suitable for a flow rate of 3.5 l/min can also be used for a sampling duration of 2 hours. The collected methanesulfonic acid deposited on the filter is extracted by means of an aqueous sodium carbonate/sodium hydrogencarbonate solution and analysed by means of ion chromatography using a conductivity detector. Quantitative determination is based on multiple-point calibrations with external standards. For an air sample volume of 1200 litres, the relative limit of quantification (LOQ) is 0.021 mg/m3. With LOQ less than 0.17 mg/ m3, the measurement of the short-term exposure limit (STEL) is also enabled with an air sample volume of 150 litres. The recovery is 100% and the expanded uncertainty is 22% for a 2-hour sampling and 35% for a 15-minute samplin
