Use of Thin Layer Chromatography and Phosphorimetry for Rapid Quantitative Determination of Biphenyl in Oranges

Abstract

Abstract Biphenyl, a widely used fungicide in citrus fruits, is quantitatively determined by initial extraction of the orange juice and pulp or peel, thin layer chromatographic separation of the biphenyl, and phosphorimetric measurement of the separated biphenyl. The ether extraction is quantitative and reproducible, and it requires less time than the lengthy steam distillations previously used. By the ether extraction method, the relative average deviation is only ± 0.2 ppm for orange juice and pulp containing 3.8–8.9 ppm biphenyl, and only ± 2 ppm for orange peel containing 39–65 ppm biphenyl. Thin layer chromatography quantitatively separates biphenyl from the orange essential oils, waxes, and other ether extractives in 15 minutes. Phosphorimetry provides an extremely sensitive and accurate final step in the analysis. Because the limit of detection of biphenyl by phosphorimetry is very low (4 × 10-3 µg biphenyl/ml solvent), an analysis can be carried out easily and accurately on an orange sample containing as little as 5 µg of biphenyl. The total time for the analysis of the biphenyl content in fovir different samples with four replicate determinations for each sample is approximately 2 hours.