Optimization of iron speciation (soluble, ferrous and ferric) in beans, chickpeas and lentils

A spectrophotometric method with bathophenanthroline for iron determination that makes it possible to differentiate between iron (II) and iron (III) in total soluble iron in legumes (beans, chickpeas and lentils) was optimized. Sample size, volumes of reducing agent and bathophenanthroline were selected. Matrix interferences made it necessary to apply the addition’s method. To check the quality of the method, linearity and precision (RSD%) were determined. A linear response between 0.1 and 1.8 μg Fe/ml in the assay and precision values ranging from 2.1 to 6 for instrumental precision, and from 1.6 to 1.7 and 2.7 to 9.1, for intra- and inter-day assays, respectively were obtained. The application of the method to legumes indicated: total soluble iron ranging from 0.52 (microwave cooked legumes) to 5.01 mg/100 g dry matter in raw beans. The percentage of soluble iron (II) with respect to total and soluble iron ranged from non detectable to 14.8% and from non detectable to 50%, respectively.