Determinação de impurezas inorgânicas em suplementos de ferro por DSS-GF AAS

Abstract

In this work a methodology for determination of inorganic impurities (Ag, As, Cr, Mn, Ni, Pb e Sb) by direct solid sampling with graphite furnace atomic absorption spectrometry (DSS-GF AAS) in iron glycinate chelate samples was developed. The thermal behavior of the analytes in solid samples and reference aqueous solutions was studied using pyrolysis and atomization curves. For Cr, Mn, Ni and Sb determination, 20 μL of water were added over the sample in the platform, and for Ag and Pb determination, 20 μL of a solution containing 4 μg of Pd as chemical modifier was used. The mass used in the Cr determination varied from 0,1 to 0,7 mg, for Ni masses among 0,1 and 0,9 mg were used, for As and Sb from 0,2 to 0,9 mg, for Ag masses among 0,1 and 1,9 mg were used, for Mn from 0,1 to 0,4 mg and for the quantification of Pb the used mass varied among 0,1 and 2,5 mg. The analytes characteristic mass average value in the solid sample was consistent with the value obtained in the aqueous reference solutions. Thus, aqueous reference solutions calibration was possible. The analytes investigated in this work, except for silver in samples FAQ1 and FAQ2, showed good homogeneity in the samples. The results obtained by the proposed method were compared with inductively coupled plasma optical emission spectrometry (ICP OES), inductively coupled plasma mass spectrometry (ICP-MS) and neutron activation analysis (NAA). No statistical difference was observed in As, Cr, Mn, Ni, Pb and Sb concentrations determined by different techniques. For Ag, the comparative techniques showed a higher detection limit (LD) than the Ag concentration found in the sample by DSS-GF AAS. To address this, analyte addition through reference solutions in the samples before introduction in the atomizer was used. The recovery for silver using standard solutions was greater than 97%. The Ag, Cr, Mn, Ni, Pb and Sb LDs obtained by DSS-GF AAS were 0,002; 0,07; 0,03; 0,01; 0,002; 0,008 and 0,08 μg g-1, respectively. With exception of As and Sb, the other elements presented lower LDs than those obtained by ICP-MS, ICP OES and NAA techniques.