A method for the simultaneous determination of 34 pesticides in sunflower oil, soybean oil and corn oil was developed. The samples were extracted and purified by a modified QuEChERS method, and then the supernatant was analyzed by on-line gel permeation chromatography-gas chromatography-mass spectrometry ( GPC-GC-MS ) . The linear range was from 0 . 01 to 0 . 2 mg/L with a good correlation coefficients ( r≥0. 9913). The average recoveries of 31 pesticides (except p,p′-DDE, p,p′-DDD, p,p′-DDT. For detail, please reference to section 3 . 6 ) ranged from 70 . 3% to 115 . 4%, 69 . 5% to 112 . 6% and 70 . 2% to 116 . 1%spiked at 0. 05 μg/g and 0. 1 μg/g with the relative standard deviations (RSDs, n=6) less than 13. 3%, 13. 5% and 12. 1% in sunflower oil, soybean oil and corn oil samples, respectively. The LODs of this method ranged from 0. 0692 to 2. 28, 0. 0559 to 2. 01 and 0. 0584 to 2. 14μg/kg (S/N=3) in sunflower oil, soybean oil and corn oil samples respectively. The convenient operation and versatility of this method are suitable for the fast screening and detection of 34 pesticide residues in sunflower oil, soybean oil and corn oil.

Objective: To optimize the determination of pentachlorophenol in wooden chopping boards through pretreatment of miniaturized samples. Methods: The pretreated wooden chopping board samples were subjected to ultrasound extraction (1 mL of 0.5 mol/L K2CO3 added in 5 mL extraction solution) in 8 mL acetone and 2 mL water, followed by derivatization with 0.3 mL acetic anhydride, extraction with n-hexane and separation with DB-5ms column (30 m×0.25 mm, 0.25 μm). Gas chromatography tandem mass spectrometry (GC-MS/MS) was performed in multiple reaction monitoring (MRM) mode with quantitative analysis using the internal standard method. Results: The GC-MS/MS assay showed a good linear relationship within the range of 0.01 to 0.2 µg/mL (R2>0.999), with a 0.003 mg/kg limit of detection and 0.01 mg/kg limit of quantitation. The mean recovery rates were 84.2% to 96.7% at spiked concentrations of 0.003, 0.01 and 0.03 mg/kg, with relative standard deviation of 2.2% to 6.1%. Conclusions The established GC-MS/MS assay is easy to perform, environment-friendly, highly accurate and sensitivity, which is feasible for determination of pentachlorophenol in wooden chopping boards.