Abstract: An isotope dilution gas chromatography-tandem mass spectrometry (GC-MS/MS) method was applied to determine 27 phthalate ester residues in pastry. Samples were extracted with a mixture of n-hexane and ethyl acetate (1:1, V/V) and the extract was cleaned up on a C18 column, detected by GC-MS/MS under multiple-reaction monitoring (MRM) mode, and quantified by an isotope internal standard method. The calibration curves of 23 out of 27 phthalate esters tested showed good linearity in the range of 0.05–10 mg/L, while those of di-n-octyl phthalate (DNOP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP) and phthalic acid, bis-dodecyl ester (DLP) were highly linear in the range of 0.1–20 mg/L, all with correlation coefficients greater than 0.99. The limits of detection (LODs) were in the range of 0.000 1–0.009 8 mg/kg and the limits of quantification (LOQs) ranged from 0.000 5–0.032 6 mg/kg. The recoveries of the proposed method for 20 different pastries at spiked levels of 0.1, 0.2 and 2.0 mg/kg were 74.3%–117.5% with relative standard deviations (RSDs) of 2.9%–13.5%. The method is simple and sensitive with a wide linear range, and can be suitable for the determination of phthalate ester residues in pastry.

Key words: phthalate eaters, pastry, gas chromatography-tandem mass spectrometry (GC-MS/MS), isotope dilution