GC-MS/MS Determination of Residual Amounts of 107 Pesticides in Okra

The pounded okra sample (10.0 g) was extracted with 10 mL of a mixture of CH3COOH-CH3CN (1+99) and 5 g of NaCl by homogenization for 2 min and centrifugation for 5 min. 2.00 mL of the supernatant was taken and mixed with 150 mg of anhydrous MgSO4, and 25 mg each of PSA and C18 for purification by swirling for 1 min and centrifuging for 3 min. 1.00 mL of the supernatant was taken and 4 μL of 100 mg·L-1 heptachlorepoxide solution was added to it as internal standard. This mixed solution was used for GC-MS/MS determination of 107 pesticides as residues in okra. Temperature-programmed sample introduction and Rxi-5Sil MS quartz capillary chromatographic column were used in GC separation. EI and MRM mode were adopted in MS/MS analysis. As shown by the results, linearities were found for 107 pesticides in the same range of 0.040-0.80 mg·L-1, with detection limits (3S/N) ranged from 0.5 to 8 μg·kg-1. Test for recovery was made by standard addition method at 3 concentration levels, giving values of recovery in the range of 65.1%-109%, and values of RSD (n=6) found wre in the range of 2.0%-9.6%.