THE USE OF CHROMAZUROL S IN THE PRESENCE OF A MIXTURE OF CATIONIC AND NON-IONIC SURFACTANTS FOR THE SPECTROPHOTOMETRIC DETERMINATION OF IRON IN CEREALS

摘要

Simple and sensitive methods for the spectrophotometric determination of iron(III) in food, based on the formation of coloured complexes of Fe(III) with Chromazurol S (CAS) in the presence of tetradecyltrimethylammoni-um bromide (TTA) or octadecyltrimethylammonium chloride (ODTA) and TritonX-100 (TX100), have been developed. Optimum pH and the concentrations of CAS, TTA, ODTA and TX100 ensuring maximum absorbance have been deteimined. For the Fe-CAS-TTA-ТХЮО system the molar absorptivity is 1.12x 10~5 L/(mol cm) at 650 nm; for Fe-CAS-ODTA-TXIOO it is 1.35 x 10~5 L/(mol cm) at 659.5 nm. Beer's law was obeyed for iron concentration in the range 0.08-0.56 mu g/mL for the complex Fe-CAS-TTA-ТХЮО and 0.08-0.64 mu g/mL for Fe-CAS-ODTA-TXIOO. Theinfluence of several interfering ions has been discussed. The stoichiometry of the complexes was established by applying Job's method. The more sensitive method, based on the Fe-CAS-ODTA-TXIOO system, has been applied to the determination of iron in cereals. To evaluate the accuracy of the elaborated method, the determined content of Fe was compared to the declared value as well as to the result obtained by the reference ICP-OES method.