Simultaneous determination of phthalate diesters and monoesters in soil using accelerated solvent extraction and ultra-performance liquid chromatography coupled with tandem mass spectrometry

Abstract Phthalate diesters are a group of plasticizers extensively used in the manufacturing and processing of plastics. Phthalate monoesters are the primary degradation products of the diesters. Accumulation of endocrine disruptive diesters and monoesters in soil is of great concern because of the extensive use of plastic mulching and misdisposal of plastics. Accurate determination of their levels in soil is critical to assess the occurrence, exposure, and risks of phthalate diesters and monoesters. In this study, we aimed to develop a robust and environmentally friendly method for the simultaneous determination of phthalate diesters and monoesters in soil. Ultra-performance liquid chromatography coupled with electrospray tandem mass spectrometry was used for quantification, combined with accelerated solvent extraction and in-line cleanup for sample preparation. The method detection limits for the 14 diesters and 11 monoesters were in the range of 0.59 to 10.08 ng g-1 d.w. Acceptable recoveries (69%–131%) for these analytes were obtained when four deuterated analogs were used for internal calibration, and intra- and inter-day variations were less than 15%. This method was later successfully applied to five soil samples, and 8 diesters and 7 monoesters were detected with the maximum concentration up to 1142.2 ng g-1 d.w. The method developed in this study can be used for screening and accurate quantification of phthalate diesters and monoesters in soil and possibly in other environmental matrices.