DETERMINATION OF THE PESTICIDE DIFLUBENZURON IN MUSHROOMS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION MASS-SPECTROMETRY

A method using high-performance liquid chromatography-atmospheric pres sure chemical ionisation mass spectrometry (HPLC-APCI-MS) has been dev eloped and validated for the determination of the insecticide difluben zuron [1-(4-chlorophenyl)-3-(2,6-diffuorobenzoyl)urea] in mushrooms. S amples were homogenised with acetone, extracted into dichloromethane-c yclohexane and further cleaned-up by size-exclusion chromatography (SE C). HPLC was performed on an ODS column with methanol-water at 1 ml/mi n. The limit of detection was 0.02 ng/mu l (equivalent to 0.017 mg/kg in the crop). The calibration was linear over the range 0.025-1.0 ng/m u l. Recovery of diflubenzuron from spiked mushrooms (0.06-0.58 mg/kg) was 85.5% with a relative standard deviation of 14.5% (n = 56).