Determination of benzoylurea insecticides in apples and pears by solid-phase extraction cleanup and liquid chromatography with UV detection

A liquid chromatographic (LC) method was developed and statistically valida ted for simultaneous determination of 5 benzoylurea insecticides (diflubenz uron, triflumuron, teflubenzuron, flufenoxuron, and lufenuron) in apples an d pears. It involves preliminary extraction with ethyl acetate-sodium sulfa te and cleanup on silica solid-phase extraction cartridges using dichlorome thane-2-propanol (9 + 1) as eluant. The eluate is dried under nitrogen and redissolved in methanol. Benzoylurea insecticides are determined by reverse d-phase LC with gradient elution at 42 degrees C and UV diode array detecti on. Recoveries from samples fortified with the 5 insecticides at 0.02-0.5 m g/kg ranged from 83 to 102% for apples and from 75 to 99% for pears. Relati ve standard deviations were 0-12%. Limits of detection were 0.01 mg/kg for apples and 0.02 mg/kg for pears.