direct and simultaneous determination of copper and iron in flours by solid sample analysis and high-resolution continuum source graphite furnace atomic absorption spectrometry

In this work, a simple, fast, and robust method was developed for the direct and simultaneous determination of copper and iron in flours using solid sample analysis and high-resolution continuum source graphite furnace atomic absorption spectrometry. the secondary lines at 217.894 and 217.812 nm were used for all simultaneous measurements of copper and iron, respectively. the pyrolysis and atomization temperatures were of 1400 and 2400 °c, respectively, and no chemical modifier was necessary. the slope of calibration curve obtained, using the rice flour certified reference material (nist 1568a) as solid standard, presented no significant difference when compared with the slope of external calibration curve using aqueous standard, at 95 % confidence level. under these conditions, the limits of quantification obtained were 0.38 (cu) and 0.11 (fe) mg kg−1, respectively. the relative standard deviations (rsd) varied from 0.5 to 14 % for copper and from 4.9 to 17 % for iron. the method accuracy was confirmed by analysis of two certified reference materials, rice flour nist 1568a and wheat flour nist 1567a, and the results were in agreement with the certified values, at 95 % confidence level. the proposed method was applied for the analysis of flour samples (corn, wheat, and white bean), both of conventional and organic cultivation. the concentration values varied in the range of 0.6–5.9 mg kg−1 for copper and of 2.6–50.4 mg kg−1 for iron. the iron concentrations in all samples analyzed were not in agreement with the value established by the brazilian legislation, which is of 42 mg of iron per kilogram of flour.