GC-MS Determination of 16 Phthalates in Vegetable Oils with Isotope Dilution Internal Standard

The sample of vegetable oil (0.400 0 g) was mixed with 20 μL of mixed internal standard solution, and the mixture was extracted ultrasonically for 15 min with 4 mL of acetonitrile. After centrifugation, the extract was purified on activated SILICA/PSA mixed glass SPE column. The purified solution was dried by N₂-blowing, and the residue was dissolved and dilued to 1.0 mL with hexane. DB-5MS UI column was used for gas chromatography separation. EI and SIM were adopted in MS, and isotope dilution internal standard method was used for quantification. Linearity ranges for 16 phthalates were obtained to be same between 0.01-1.00 mg·L^-1, with detection limits (3S/N) in the range of 0.003 0-0.035 mg·kg^-1. Test for recovery was made by standard addition at 3 concentration levels, giving results in the range of 81.7%-113%, with RSDs (n=6) ranged from 2.8% to 11%.