Assessment of the stability of pesticides during the cryogenic processing of fruits and vegetables.

An evaluation of the stability of pesticides in fruit and vegetables during cryogenic sample processing (comminution of samples in the presence of dry ice) is reported. Pesticides were spiked onto the undamaged surface of individual units of fruit before freezing and comminution. The mean recoveries of pesticides spiked before and after comminution of the sample were compared to determine the relative stability of the individual pesticides during cryogenic sample processing. A stable internal deposition standard (IDS) was used to correct for physical losses and volumetric errors. Mean recovery results together with associated standard errors were obtained using restricted maximum likelihood (REML) analysis. A total of 134 pesticides in four commodities (apples, grapes, lettuce and oranges) were evaluated. The results demonstrated that 120 pesticides were stable (i.e. the mean difference in recovery of pesticides spiked pre- and post-processing was <20%) during cryogenic sample processing. Fourteen pesticides showed some instability or loss (i.e. the mean difference in recovery of pesticides spiked pre- and post-processing was >20%) during cryogenic sample processing: biphenyl, cadusafos, captan, chlorothalonil, dichlorvos, disulfoton, ethoxyquin, etridiazole, heptenophos, malaoxon, phorate, tebuconazole, tecnazene and trifluralin.