COLORIMETRIC DETERMINATION OF IRON IN INFANT FORTIFIED FORMULAS BY SEQUENTIAL INJECTION-ANALYSIS

A procedure is described for the colorimetric determination of iron in infant fortified formulas based on sequential injection analysis (SIA ). Iron(III) complexation with thiocyanate is used as colour developin g reaction. The system enables the determination of iron in the sample s (after digestion by dry ashing and treatment with 0.2 mol/L nitric a cid in the range of 0.50-20.0 mg/L, consuming 140 mu L of the sample a nd 8 mg thiocyanate per determination. The reactor geometry and the ad justment of the ionic content of the calibration solutions is importan t for the accuracy of the results. A regression line according to the equation [Fe(III) (mg/L)](SIA) = - 0.3(+/- 0.4) + 1.03(+/- 0.04) [Fe(I II) (mg/L)](FAAS) was obtained after comparative analysis of a set of 12 samples. The measurement rate was 34 s, thus allowing to analyze 10 0 samples per hour with a relative standard deviation lower than 2%.