Determination of iron in milk infant formulas by using Chromazurol S in the presence of dodecyltrimethylammonium bromide and Brij 35
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Two sensitive methods for spectrophotometric determination of iron(III) in milk infant formulas, based on the formation of coloured complexes of Fe(III) with Chromazurol S (CAS) in the presence of dodecyltrimethylammonium bromide (DTA) alone and DTA with Brij 35 have been developed. Optimum pH and the concentrations of CAS, DTA, and Brij 35 ensuring maximum absorbance have been determined. For the Fe-CAS-DTA system, the molar absorptivity is 1.05 × 105 L/(mol cm) at 685 nm; for Fe-CAS-DTA-Brij 35 it is 1.94 × 105 L/(mol cm) at 636 nm. Beer’s law was obeyed for iron concentration in the range of 0.04–0.40 μg/mL for the complex Fe-CAS-DTA and 0.08−0.40 μg/mL for Fe-CAS-DTA-Brij 35. The influence of several interfering ions has been discussed. The stoichiometry of the complexes was established by applying Job’s method. The method, basing on the Fe-CAS-DTA system, has been applied to the determination of iron in milk samples. 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.
Keywordsspectrophotometric determination iron in milk Chromazurol S surfactants
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