Simultaneous Determination of 23 Phthalate Esters in Soil by Multi-Plug Filtration Cleanup Combined with Gas Chromatography-Triple Quadrupole Tandem Mass Spectrometry

The soil sample (20.00 g) that had been removed from impurities and mixed well, was taken and about 4 g of diatomite was added. After stirring, water absorption and mixing well, accelerate solvent extraction was run for 5 min at 100 ℃ and 10 MPa with the mixed solution of n-hexane and acetone at volume ratio of 1∶1 as the extraction solvent and cycled twice. The extract was concentrated to 5-8 mL by rotary evaporation, and then switched twice with n-hexane to remove water (adding 5 mL of n-hexane once). After removing water with anhydrous sodium sulfate, the solution was blown to 1 mL at 37 ℃ by nitrogen. 20 μL of 4 000 mg·L⁻¹ 5 deuterated internal standard mixed solution was added and mixed well. The mixture was purified using multi-plug filtration cleanup (m-PFC) column, in which 23 phthalate esters (PAEs) were separated on HP-5MS UI column by column heating program. Electron impact ion source and multiple reaction monitoring mode were adopted in mass spectrometry analysis, with internal standard method for quantification. As shown by the results, m-PFC technology could reduce the pre-treatment process and decrease laboratory blank. Linear relationships between the peak area ratios of PAEs to the corresponding internal standards and mass concentrations of 23 PAEs were found in definite ranges, with detection limits (3.143s) in the range of 0.004-0.23 μg·kg⁻¹. Test for recovery was made on the blank soil samples by the standard addition method, giving results in the range of 64.5%-129%, with RSDs (n=6) of the determined values in the range of 0.40%-15%. This method was used for analysis of 10 actual soil samples, and dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP), and dibenzyl phthalate were detected, with detection amounts in the range of 1.04-36.9 μg·kg⁻¹.