THE ANALYSIS OF CYHEXATIN RESIDUES IN APPLES, PEARS AND KIWI FRUIT USING INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY AS AN INITIAL SCREEN FOR TOTAL TIN, WITH CONFIRMATION BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

Inductively coupled plasma-mass spectrometry (ICP-MS) has been used to determine concentrations of total tin in samples of apples, pears and kiwi fruit, following acid digestion. It was found that the backgroun d levels of tin in these fruits were normally below 0.06 mg/kg, which was equivalent to the target reporting limit for cyhexatin for this wo rk of 0.2 mg/kg. The procedure was used to screen a total of 72 retail samples. Three apple samples contained tin at concentrations greater than 0.06 mg/kg. These three samples were re-analysed by a second conf irmatory method wing gas chromatography-mass spectrometry (GC-MS) as t he determinative step. Results obtained by this method demonstrated th at, in fact, none of the samples contained cyhexatin residues at or ab ove a reporting limit of 0.1 mg/kg. The use of ICP-MS as a preliminary screen substantially reduced the number of samples requiring analysis by GC-MS, thus reducing the cost of the survey (in terms of staff hou rs) by approximately 30%. The screening method could potentially be ap plied to other organometallic pesticide residues.