Simultaneous determination of iron and nickel as contaminants in multimineral and multivitamin supplements by solid...

A methodology to assay simultaneously iron and nickel present as contaminants in multimineral and multivitamin supplements was investigated. High-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis were used. Measurements were done with the secondary lines of Fe (352.604 nm) and Ni (352.454 nm) to avoid spectral interferences. The best temperatures for pyrolysis and atomization for Fe and Ni were 1000 and 2700 °C, respectively. Chemical modifiers were not necessary and no matrix effects were observed. Aqueous standard solutions were used for calibration. The limit of detection was 0.517 µg g^-1 for Fe and 0.011 µg g^-1 for Ni. The precision ranged from 4.3% to 17% and 4.4-20% for Fe and Ni, respectively. The method accuracy was confirmed by comparing statistically the results obtained by solid sampling with those of sample acid digestion. The proposed methodology was successfully applied to determine both metals in different multimineral and multivitamin supplements.