Benzoic acid - Determination of benzoic acid in workplace air using high-performance liquid chromatography...

The working group "Air Analyses" of the German Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) developed and verified the presented analytical method. This analytical method permits the determination of benzoic acid [65-85-0] 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 0.5 mg/m³. Sampling is performed using a flow-regulated pump to draw a defined volume of air through a binder-free quartz fibre filter followed by a sorbent tube filled with silica gel. The volumetric flow rate is 1 l/min and the sampling duration is 2 hours (which corresponds to a sampling volume of 120 l). The collected benzoic acid is extracted with methanol and subsequently analysed by means of high-performance liquid chromatography using diode array detection. Quantitative determination is based on a multiple-point calibration function. For an air sample volume of 120 litres, the relative limit of quantification (LOQ) is 0.0023 mg/m³. The mean recovery is 96.3% and the expanded uncertainty for the validation range of 0.05 to 1 mg/m³ is 18%.