Adipic acid. Determination in workplace air

Abstract

Adipic acid is a colorless or white solid. On an industrial scale it is obtained by oxidation of cyclohexanol, cyclohexanone or their mixtures with nitric acid. The compound is utilized in the chemical industry in the production of polyurethanes, polyamides and in the food industry, e.g., as an acidity regulator (E355). Adipic acid is irritating to the eyes. The aim of this study was to develop a method for determining inhalable fraction of adipic acid which enables determination of its concentrations in workplaces air in the range from 1/10 to 2 of MAC values. The developed method is based on the adsorption of adipic acid on a glass fiber filter, a water-extraction and a gas chromatographic analysis of the resulting solution. The tests were performed using a liquid chromatograph (HPLC) 1200 series of Agilent Technologies with diode array detector (DAD). Determinations were performed with application of Allure Organic Acids column (15 cm x 4.6 mm, dp 5 µm). Validation of the method was conducted in accordance with the requirements of the Standard No. EN 482. On the basis of the obtained results, the concentration range was established as 0.036 – 0.72 mg/ml, which corresponds to the concentration range of 0.5 – 10 mg/m3 for 720-L air sample. In the following range the obtained calibration curve was linear as evidenced by the regression coefficient at the level of 0.9999. The overall accuracy of the method was 5.47% and its relative total uncertainty 23.88%. This method enables selective analytical determination of adipic acid in workplace air at the concentration range 0.5 – 10 mg/m3 in the presence of cooccurring compounds, such as cyclohexanone and isopropanol. The method for determining adipic acid is described in the form of analytical procedure in the annex.