Application of an improved steam distillation procedure in residue analysis. Part I. Determination of biphenyl and 2-phenylphenol in citrus fruits

Abstract

An improved steam distillation method for the separation of biphenyl and 2-phenylphenol from citrus fruits is described. The method involves the steam distillation of both fungicides from citrus fruits into a non-alkaline trap for the collection of biphenyl and into three alkaline traps for the collection of 2-phenylphenol. After distillation, the heptane extract is directly analysed for biphenyl by means of gas-liquid chromatography with flame-ionisation detection and the alkaline solution is analysed for 2-phenylphenol by means of gas-liquid chromatography with electron-capture detection after pentafluorobenzoylation and extraction with heptane. This method of steam distillation gives satisfactory clean-up from essential oils and the limit of detection of the method is 1.25 p.p.m. for biphenyl and 0.13 p.p.m. for 2-phenylphenol. Recoveries of biphenyl and 2-phenylphenol from lemon, orange and grapefruit were satisfactory.