DETERMINATION OF THE PESTICIDE FENBUTATIN OXIDE IN TOMATOES, CUCUMBERS AND BANANAS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ATMOSPHERIC-PRESSURE CHEMICAL IONIZATION-MASS SPECTROMETRY

A rapid method, using high-performance liquid chromatography (HPLC)/at mospheric pressure chemical ionization-mass spectrometry, has been dev eloped for the determination of fenbutatin oxide in tomatoes, cucumber s and bananas. Samples were homogenized with sodium carbonate and ethy l acetate, filtered through sodium sulphate, concentrated and solvent exchanged into acetonitrile prior to analysis, HPLC was performed on a Hypercard column with 10:90 acetic acid (5% v/v glacial acetic acid i n water)/acetonitrile at a flow rate of 1 mL/min. Positive ionization selected-ion monitoring was performed on the 7 isotopic cluster ions f rom the tris(2-methyl-2-phenylpropyl) fin fragment; A comparison of so lvent-based and extract-based standards showed that tomato and cucumbe r matrices had a slight enhancement effect on the signal intensity, wh ereas the banana matrix exerted a signal suppression effect. Calibrati on was linear over the range 0.25-5.0 ng/mu L. The mean spike recoveri es (extracts spiked at 0.5 mg/kg) were 88% for tomatoes and 80% for bo th cucumbers and bananas with relative standard deviations of 6%, 7% a nd 8% respectively. Limits of detection mere commodity dependent and r anged from 0.06-0.12 ng/mu L (equivalent to 0.01-0.02 mg/kg in the cro p). Ionization was stable for long analytical time periods. (C) 1997 C rown Copyright.