Simultaneous Determination of Chromium and Iron in Powdered Milk Using High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry

This work proposes the simultaneous determination of chromium and iron in powdered milk samples using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) and sample digestion in microwave oven using nitric acid and hydrogen peroxide. The method was established using the primary line (357.869 nm) for chromium and the adjacent secondary line (358.120 nm) for iron while employing aluminum as the chemical modifier. The absorbance signals were measured by peak area using three pixels for both elements. Chromium and iron can be determined in powdered milk samples by the external calibration technique with limits of quantification of 28 ng g−1 for chromium and 19 μg g−1 for iron. The precision was evaluated by using a milk sample with chromium and iron concentrations of 0.76 μg g−1 and 151.3 μg g−1, respectively. The results expressed as relative standard deviation (n = 10) were 2.6% for iron and 3.9% for chromium. The method accuracy was confirmed by the analysis of a milk sample by a comparison of results obtained by the proposed method and those found by employing inductively coupled plasma mass spectrometry (ICP-MS). Five samples were analyzed, and the analyte concentrations found varied from 408 to 805 ng g−1 for chromium. Among the five samples, three had an iron concentration lower than 19 μg g−1 and in the other two samples, the iron concentrations varied from 151 to 199 μg g−1.