Determination of 21 pesticides in agricultural products by HPLC-photodiode array detection

A screening method using HPLC for the simultaneous determination of 21 pesticides in agricultural products has been developed. The pesticides were extracted from samples with acetonitrile. The extract was cleaned up on a gel permeation column and a silica gel cartridge. The silica gel cartridge was eluted with 5% acetone-hexane (A/H), 35% A/H, 60% A/H, and 30% methanol-acetone, successively. The eluates were concentrated and analyzed on a high performance liquid chromatograph equipped with a photodiode array detector, using an Inertsil ODS-2 column (150X4.6 mm i.d.) with a gradient system of 0.003 mol/L phosphoric acid-acetonitrile as the mobile phase at a flow rate of 1.0 mL/min. The recoveries at the level of 0.4 mu g/g were 62 similar to 120%, except for bentazon in banana and quinclorac in 5 crops tested. Detection limits were 0.005 similar to 0.02 mu g/g for the 21 pesticides.