Determination of phthalates in soils and biosolids using accelerated solvent extraction coupled with SPE cleanup and GC–MS quantification

• An accelerated solvent extraction method for extraction of phthalates
• Measuring phthalates in nanogram per kilogram of soil
• A robust hyphenated ASE–SPE–GC–MS method for analysis of phthalates
• Determination of phthalates in different soils and biosolids

A rapid highly sensitive method based on accelerated solvent extraction (ASE) coupled with solid phase extraction (SPE) and gas chromatography mass spectrometry (ASE–SPE–GC–MS) has been developed for the analysis of seven commonly identified phthalates found in soil and biosolids including: dimethyl phthalate (DMP), diethyl phthalate (DEP), benzylbutyl phthalate (BBP), bis(2-diethylhexyl phthalate) (DEHP), di-n-octyl phthalate (DnOP), dipentyl phthalate (DPP) and di-n-butyl phthalate (DnBP). The developed method is capable of measuring phthalates in 15 min with sensitivity in the tenth of ng kg− 1 range. Parameters for ASE were investigated to render maximum efficiency of phthalate recovery using a tri-solvent extraction (ethyl acetate, hexane, dichloromethane) in a 2:3:2 ratio along with different temperatures and static periods. A detailed oven program was developed for the GC–MS analysis in which seven major phthalates were separated. The results obtained for recovery of phthalates ranged from 85 to 111% in tests on field soils and an alkaline treated biosolid. The method was successfully validated for the SPE extraction efficiency and the loss of content. The optimized method resulted in high sensitivity of measurement with the LOD ranging from 0.03 ng kg− 1 to 0.27 μg kg− 1 and the LOQ ranging from 0.1 ng kg− 1 to 0.87 μg kg− 1 with the RSD ranging from 4.4 to 9.8%. Concentrations of phthalates recovered in an agricultural field soil ranged from 0.03 ± 0.01 to 0.15 ± 0.04 ng g− 1 but were measured at 0.63 ± 0.1 to 4.3 ± 0.48 ng g− 1 in the same soil receiving an alkaline treated biosolid (ATB) amendment. The concentrations of phthalates found in the ATB used in the field soil ranged from 2.8 ± 0.81 to 8.3 ± 0.73 ng g− 1, and the concentrations of phthalates in the raw untreated sewage solids (w/w) ranged from 3.4 ± 0.79 to 14.9 ± 1.3 ng g− 1.