Determination of pyrethroid residues in vegetables, fruits, grains, beans, and green tea leaves: applications to pyrethroid residue monitoring studies.

Determination of natural pyrethrins and 12 synthetic pyrethroids in agricultural products was investigated. Vegetables and fruits were extracted with acetone, filtered after addition of coagulating solution, partitioned into n-hexane, and cleaned up on a Florisil column (as necessary). Pyrethroids were determined by gas chromatography/electron capture detection (GC/ECD) by using a methyl silicone-coated fused-silica capillary column, and recoveries were calculated by summing peak areas of the components. GC/mass spectrometry was used to identify the pyrethroids detected by GC/ECD monitoring. Grains and beans containing lipids were analyzed by extraction with acetonitrile, partition into n-hexane, Florisil column cleanup, and capillary GC/ECD. The coagulation method was suitable for nonfatty crops such as vegetables, fruits, and green tea leaves, because recoveries were good and Florisil column cleanup was not needed in most cases. The coagulation method was not applicable to lipid-containing crops such as grains and beans because of low recoveries. Recoveries for 18 crops at fortification levels of 0.25-1.0 ppm were 60.0-103.5%. No pyrethroids were detected from the nonfortified crops tested except green tea leaves, in which fluvalinate was detected at 0.89 ppm.