Zitronensäure – Bestimmung von Zitronensäure in der Luft am Arbeitsplatz mittels Hochleistungsflüssigchromatographie (HPLC) [Air Monitoring Methods in German language, 2019]

This analytical method is a validated measurement procedure for the determination of citric acid [77‐92‐9] in workplace air in a concentration range of one tenth up to twice the currently valid OEL or MAK value of 2 mg/m3 E. Sampling is performed by drawing a defined volume of air through a glass fibre filter, which is inserted in a GSP sampling system. using a suitable flow‐regulated pump with a volumetric flow rate of 10 L/min or 3,5 L/min. For sampling 2 hours or 15 min (checking the short‐term value) can be used. The collected citric acid is extracted with diluted caustic soda and analysed by means of high performance liquid chromatography using an UV detector. The quantitative determination is based on a calibration function obtained by means of a multiple‐point calibration. The absolute limit of quantification (LOQ) is 12 ng and the relative LOQ is 0.005 mg/m3 based on an air sample volume of approx. 1200 L (0.014 mg/m3 based on air sample volume of 420 L) or 0.04 mg/m3 based on an air sample volume of approx. 150 L (for short‐term value) (0.11 mg/m3 based on air sample volume of 52.5 L). The mean recovery was 100% and the expanded uncertainty for the overall measurement method was 18%