A simple and selective method for determination of phthalate biomarkers in vegetable samples by high pressure liquid chromatography–electrospray ionization-tandem mass spectrometry

• Clean-up techniques of phthalate monoesters from vegetable samples were optimized.
• Sample preparation based on ultrasonic extraction followed by liquid–liquid extraction.
• Quantification of phthalate monoesters in vegetable samples by LC–MS/MS was developed.

In the present study, solid-phase extraction cartridges including silica reversed-phase Isolute C18, polymeric reversed-phase Oasis HLB and mixed-mode anion-exchange Oasis MAX, and liquid–liquid extractions with ethyl acetate, n-hexane, dichloromethane and its mixtures were compared for clean-up of phthalate monoesters from vegetable samples. Best recoveries and minimised matrix effects were achieved using ethyl acetate/n-hexane liquid–liquid extraction for these target compounds. A simple and selective method, based on sample preparation by ultrasonic extraction and liquid–liquid extraction clean-up, for the determination of phthalate monoesters in vegetable samples by liquid chromatography/electrospray ionisation-tandem mass spectrometry was developed. The method detection limits for phthalate monoesters ranged from 0.013 to 0.120 ng g−1. Good linearity (r2 > 0.991) between MQLs and 1000× MQLs was achieved. The intra- and inter-day relative standard deviation values were less than 11.8%. The method was successfully used to determine phthalate monoester metabolites in the vegetable samples.