Accelerated solvent extraction combined with GC–MS: A convenient technique for the determination and compound-specific stable isotope analysis of phthalates in mine tailings

Abstract

A reliable, simple and fast method was developed to detect four phthalic acid esters (PAEs) including dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) and diethylhexyl phthalate (DEHP) in mine tailings based on the accelerated solvent extraction (ASE) combined with gas chromatography-mass spectrometry (ASE/GC–MS). Evaluation of extraction parameters including choice of extraction solvent, temperature, extraction time, and number of extraction cycles showed that dichloromethane, 120 °C, 3 min, and 2 cycles were optimal, respectively. Under these conditions, the limit of detection (LOD) and limit of quantitation (LOQ) values were in the range of 1.2–2.0 µg kg–1 and 3.0–4.6 µg kg–1, respectively, and precision of the analytical data, RSD ≤ 7.0% were determined. This method was used to analyze the PAEs-spiked mine tailing samples (100 µg kg–1 of each analyte). Acceptable recovery values of 71.3–77.1%, 100–110%, 105–116%, and 101–115% were obtained for DMP, DEP, DBP and DEHP, respectively. The technique was also successfully applied for the extraction of the PAEs in real samples collected from mine tailing pond. Finally, stable C and H isotope analyses were conducted using GC coupled to isotope ratio MS to investigate effect of the ASE method on H and C isotopic compositions of the target analytes. Results showed that the ASE procedure did not lead to significant isotope fractionation of the compounds. Overall, the major advantages of this method are: automated operation, high sensitivity, short extraction time, less solvent consumption, and compatibility with a variety of detecting equipment. Combined with CSIA, it could be used to study the degradation mechanisms of target PAEs in mine tailing environments.