Determination of ortho-phenylphenol, diphenyl and diphenylamine in apples and oranges using HPLC with fluorescence detection

A reversed-phase high performance liquid chromatographic (RP-HPLC) method for the determination of the fungicides ortho-phenylphenol (OPP), diphenyl (DP) and diphenylamine (DPA) is developed. A mobile phase consisting of methanol:water (70:30) and fluorescence detection (Ex and Em set at 285 and 340 nm, respectively) was used. The fungicide residues were extracted with ethyl acetate, and concentrated prior to the HPLC analysis. The proposed HPLC method was clearly superior as compared to an earlier report that was based on a mobile phase of acetonitrile:methanol:water (47:13:40 v/v) for the determination of DP, OPP and thiabendazole, especially with respect to lower detection limits and faster analysis times. Limits of detection were 0.005, 0.100 and 0.02 ppm for OPP, DP and DPA, respectively. Recovery studies that were done by fortifying apples and oranges at 0.25 and 0.50 ppm levels respectively, were satisfactory (average percent recoveries of 108.8 and 84.0%, respectively for apples and oranges). Results on the determination of these fungicides in several apple and orange samples will also be discussed.