Multivariate Optimization in the Direct Determination of Antimony and Chromium in Serum Samples by Graphite Furnace Atomic Absorption Spectrometry

Methods for direct determination of antimony and chromium in human serum by Graphite Furnace Atomic Absorption Spectrometry (GF AAS) were proposed in this work. The samples were diluted in 1:1 with nitric acid 1% v/v and Triton® X-100 0.1% v/v. The optimization of the instrumental conditions was done using a multivariate approach. A factorial design (2) was employed to investigate the tendency of the most intense absorvance signal for each analyte. Permanent zirconium modifier (500 μg) demonstrated better performance for use as a chemical modifier for antimony while for chromium, the best modifier was permanent tungsten. A Central Composed Design (CCD) was used to obtain the optimum conditions through the methodology of surface response, resulting in the best temperatures of 700 oC and 2400 oC for pyrolysis and atomization temperatures for antimony and 1600 oC and 2504 oC for chromium, respectively. The method allowed the determination of antimony with a curve varying from 0 to 30.0 μg L. Recovery studies for three concentration levels (n=7 for each level, prepared and read in three consecutive days) presented results of 101 ± 3 % for Sb and 93 ± 7 % for Cr. The detection limit was 0.3 g L for Cr and Sb. Intra and inter-assay studies, according to coefficients of variation results, were 2.6-2.8 % and 4.3-5.6 % for Sb and 3.0-5.5 % and 6.2-9.9 % for Cr, respectively. The method was applied for the determination of antimony in 60 samples obtaining concentrations from < LOD to 10.9 μg L and for Cr with concentrations between < LOD to 41.8 μg L.