A colorimetric method for the determination of 2-phenylphenol residues in citrus fruits

Abstract

A colorimetric method for the determination of 2-phenylphenol residues in citrus fruit, based on a specific colour reaction given by 2-phenylphenol with sulphuric acid, trace amounts of formaldehyde and iron(III), is described. 2-Phenylphenol is extracted from the fruit with chloroform, transferred into an alkaline medium, and, after acidification of the latter, re-extracted with chloroform. The extract is purified with 86·3 per cent. w/w sulphuric acid and the 2-phenylphenol is then determined colorimetrically. The method permits the determination of small amounts of 2-phenylphenol of the order of 0·05, 0·3 and 0·1 p.p.m. in the pulp, peel and whole fruit, respectively. The recovery of 2-phenylphenol varies between 95 and 106 per cent.