ICP- quadrupole MS for accurate determination of chromium in environmental and food matrices
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Chromium determination in different matrices is very important, whether due to the harmful or beneficial effects of this element. The quantification of chromium present at very low concentrations in foods and environmental samples requires the use of highly sensitive analytical techniques, such as inductively coupled plasma mass spectrometry (ICP-MS). A major difficulty of ICP-MS concerns the overlap of spectral interferences with the analyte signal, which can be addressed using various strategies. In this work, a single method was proposed for Cr determination in different matrices, and the instrumental conditions were optimized with evaluation of the accuracy using CRMs of water (NIST 1640a), fish tissue (DORM-4), and soil (NIST 2709a). Statistical analysis showed that the best results for interference removal were obtained using a collision gas (helium) flow rate of 3 mL min−1, which provided the lowest LOD, LOQ, and RSD values, with the highest accuracies in the CRM analyses. Analyses were performed in water samples collected from fountains in the municipality of Ibirá (São Paulo State), as well as still and sparkling bottled water samples. Tissue samples from different fish species (Abrotea, Pangasius, and Tilapia) were acquired in a local market and, samples of sludge and sediment were collected at Mariana city (Minas Gerais State, Brazil). The concentrations of total Cr determined in the samples of water (from 8 ± 0.1 to 34 ± 2 μg L−1) and fish tissue (from 0.056 to 0.084 μg g−1) were within the limits established by ANVISA, 50 μg L−1 for water and 0.1 mg kg−1for fish. The range concentrations in the sludge and sediment (from 127 ± 1 to 221 ± 2 μg g−1) exceeded the limit established by Brazilian Legislation (90 μg g−1), CONAMA. The analytical technique presented LODs from 0.0009 to 0.3 μg L−1, LOQs from 0.004 to 1.1 μg L−1, RSDs from 5 to 14 %, and recoveries from 91 to 105 % for the CRMs. Satisfactory precision and accuracy of the method were achieved, plus a single analytical method for all samples.