Colour reaction of iron(III) with phenylfluorone in the presence of triton X-100 and quaternary ammonium salts and its analytical application

Spectrophotometric determination of iron(III) utilizing the reaction with phenylfluorone (PF) in the presence of Triton X-100 and quaternary ammonium salts: cetylpyridinium chloride (CP), hexadecyltrimethylammonium chloride (CTA), dodecyltrimethylammonium bromide (DTA), benzyldimethyltetradecylammonium chloride (zeph) has been elaborated. Optimum concentrations of PF, Triton X-100 and cationic surfactants, the sequence of reagents addition and pH were estimated. Calibration plots for spectrophotometric determination of Fe(III) were constructed for the studied multi-component systems. It was found that the sensitivity of the elaborated methods depends on the chemical structure of cationic surfactants, mainly on the length of the alkyl chain in the quaternary ammonium salt molecule. According to the measured absorptivity solubilizing properties of the surfactants; used increase in the following order: CTA > CP > zeph > DTA. The most sensitive method (Fe-PF-CTA-Triton X-100, epsilon = 1.51 x 10(5) L mol(-1) cm(-1)) has been applied to the determination of iron in various milk samples and milk substituting preparations.