LC-MS/MS Determination of Residual Amounts of 5 Pesticides in Vegetable and Its Products

A method of LC-MS/MS for the determination of residual amounts of 5 pesticides, i.e. benalaxyl, methomyl, propazine, tebufenpyrad and pyridaben in vegetable and its products was proposed. The sample was extracted with a mixture of acetonitrile (containing φ 0.1% of acetic acid) and anhy. MgSO4 as well as anhy. NaOAc. After centrifugation, the supernatant was evaporated to dryness and dissolved with 2 mL of the CH3CN acidified with CH3COOH. The solution was then purified by dispersive-SPE through mixing vortically with PSA, C18 and graphite carbon black. The supernatant was taken and separated on Hypersil GOLD-C18 column using mixtures of (A) methanol and (B) mixture of formic acid and H2O (1+9) with different ratio as mobile phase by gradient elution. The eluate was made up to definite volume and used for MS determination. ESI- and MRM were adopted in MS/MS. Linear relationships between values of peak area and mass concentration of the 5 pesticides were kept in definite ranges, with the same detection limit (3S/N) of 0.01 mg·kg-1. Tests for recovery were made by standard addition method, giving values of recovery and RSD′s (n=6) in the ranges of 86.1%-95.7% and 1.2%-3.8% respectively.