Detection of diphenylamine on surfaces of nontreated apples (Malus domestica Borkh.)

Anecdotal reports indicate that diphenylamine (DPA) may be endogenous in apples. To test this hypothesis, hexane extracts of apples were analyzed for residues of DPA by GC/MS. DPA was detected in samples of five cultivars that had been stored for 7-8 months at 0 °C. DPA concentration was approximately 0.1 μg g -1 (fresh weight). These fruit had not been treated with DPA before storage and were not stored with DPA-treated fruit. Detection of DPA on the walls of the storage rooms indicated possible contamination by airborne residues. DPA was also detected in freshly harvested commercially grown apples at three stages of development, in samples of organically grown apples, and in a sample of freshly harvested pears. All had detectable DPA residues at approximately 10% of the concentration detected in stored fruit. Analyses of the extracts using a HFBA derivatization procedure indicated detection of DPA in the presence of a coeluting interference. Therefore, whether or not DPA is endogenous to apples and pears remains uncertain. If so, concentrations can be presumed to be <0.01 μg g -1 of fresh weight of fruit. Results have significant implications when DPA residue measurements are interpreted.