Evaluation of the calibration method on quantification of 78 pesticides in grape by gas chromatography-tandem mass spectrometry

A method was established for the simultaneous determination of 78 pesticides in grapes by QuEChERS sample preparation with a citrate buffer and gas chromatography-tandem mass spectrometry (GC-MS/MS). The quantitative results of four matrix matching calibration methods in grapes were evaluated by spiking recovery method, and the linear regression coefficient, recovery, and precision of the four calibration methods were evaluated. The results showed that when the spiking level was 0.01 mg/kg, the linear relationships between peak area and mass concentration of 78 pesticides using the four calibration methods in the range of 0.005-0.1 mg/L were good and the determination cofficients (R²) were all above 0.99, and the precision of most pesticides could meet the requirements of pesticide residue detection. However, when the matrix matched calibration that prepared with blank matrix extracts was used for calibration, whether with internal standard or not, the recoveries were not satisfactory for all the compounds. Much better recovery results were obtained using the matrix matched calibration that prepared by blank matrix spiked with standard solutions, with or without internal standard, the recoveries were in the range of 82%-114% and 81%-110%, respectively, and the relative standard deviations were 2.3%-18% and 1.2%-17%, respectively. The method meets the quality control criterion on chemical testing of foods, and is suitable for routine analysis in laboratory.