Simultaneous Determination of Two Groups of Elements in Milk by Electrothermal Atomic Absorption Spectrometry: Evaluation of Ruthenium Modifiers

Different kinds of ruthenium coatings are proposed as chemical modifiers for the simultaneous determination of two groups of elements: first, the more Volatile elements Such as As, Bi, Pb, Sb, and Se and, second, the elements Co, Cr, Cu, Fe, and Mn in milk samples by electrothermal atomic absorption spectrometry. Uncoated and coated platforms tube with Ru modifiers and co-injection of Pd+Mg were Studied. Milk samples were 1 + 9 diluted in 1.0% (v/v) HNO(3) an injected into the tube. Very long tube lifetimes were obtained for the two groups with around 750 cycles for the direct determination of the diluted milk sample. Platforms, pretreated with W-Ru, were selected for the first group and pretreated platforms with W plus RuCl(3) were selected for the second group. Calibration by matrix matching and analytical curves in the 5.0 - 20.0 mu g L(-1) range with good linear correlation coefficients were obtained. Relative standard deviations were 7.2% and the calculated characteristic masses were between 7.2 pg and 89.1 pg. The limits of detection obtained for undiluted milk samples were as follows:For Group I elements:32 mu g L(-1) for As; 36 mu g L(-1) for Bi; 29 mu g L(-1) for Se; 29 mu g L(-1) for Sb; 25 mu g L(-1) for Pb; 18 mu g L(-1) for Co.For Group 2 elements:13 mu g L(-1) for Cr; 16 mu g L(-1) for Cu; 53 mu g L(-1) for Fe; 20 mu g L(-1) for Mn.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Evaluation of different rhodium modifiers and coatings on the simultaneous determination of As, Bi, Pb, Sb, Se and of Co, Cr, Cu, Fe, Mn in milk by electrothermal atomic absorption spectrometry

Different kinds of modifiers and coatings on the integrated platform of transversely heated graphite atomizer (THGA) have been tested for the simultaneous determination of two group of elements: the first, the more volatile, formed by arsenic, bismuth, lead, antimony and selenium; the second, the less volatile, formed by cobalt, chromium, cupper, iron and manganese in milk by electrothermal atomic absorption spectrometry. Different Rh-modifiers were studied, such as Rh-coated platforms (Rh), carbide plus rhodium coated platforms (W-Rh, Zr-Rh), carbide-coated platforms (W and Zr) with co-injection of RhCl3, solutions and uncoated platforms with injection of solutions of Pd(NO3)(2), Mg(NO3)(2), and RhCl3. Milk samples were diluted 1:10 in 1.0% HNO3 and injected into the tube. The mass of modifier deposited and co-injected in the tube and the use of end capped tubes were also evaluated in order to improve the electrothermal behavior of analytes. Integrated platform pretreated with W plus co-injection RhCl3 for first group and pretreated with W-Rh for second group were elected. For 20 mu L injected samples the analytical curves in the 5.0-20.0 mu g L-1 concentration range have good linear correlation coefficients (r > 0.998). Relative standard deviations (n = 12) are < 6% and the calculated characteristic masses are between 5 pg and 62 pg

Simultaneous and Direct Determination of As, Bi, Pb, Sb, and Se and Co, Cr, Cu, Fe, and Mn in Milk by Electrothermal Atomic Absorption Spectrometry

Tungsten permanent modifier with coinjection of Pd(NO3)(2) and W-Ru permanent modifiers are proposed for the direct and simultaneous determination of As, Bi, Pb, Sb, and Se (group 1) and Co, Cr, Cu, Fe, and Mn (group 2), respectively, in milk by graphite furnace atomic absorption spectrometry. The performance of modifiers was evaluated by means of thermal behavior of analytes, sensitivity, atomic signal profile, repeatability, graphite tube lifetime, and background intensity. An air-assisted pyrolysis step was necessary to quantitative elimination of the organic matter. After methods optimization, 14 commercial milk samples were analyzed. The found concentrations of As, Bi, Pb, Sb, Se, Co, and Cr were lower than their limit of detection (2.13, 2.21, 1.49, 1.63, 2.05, 1.0, and 1.2 mu g L-1, respectively). Concentrations of Cu, Fe, and Mn were in the 1.58-5.74 mu g L-1, 9.79-49.3 mu g L-1, and 2.25-4.08 mu g L-1 intervals, respectively. The limits of detection for Cu, Fe, and Mn were 1.7, 5.3, and 2.0 mu g L-1, respectively. The accuracy of methods was checked after analysis of two milk standard materials. Results for Cr, Cu, Fe, Mn, Pb, and Mn were in agreement with certified values of SRMs at the 95% confidence level. Accuracy was also evaluated by addition-recovery tests and recoveries in the 86-127% range were obtained for all elements. The use of pretreat platform of graphite tubes with W or W-Ru allowed enlarging the lifetime of atomizer in 750 heating cycles.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Evaluation of Ir-based modifiers in the simultaneous determination of As, Bi, Pb, Sb, and Se in milk by graphite furnace atomic absorption spectrometry

Different modifiers (IrCl3, W+IrCl3, Zr+IrCl 3) and coatings (Ir, W-Ir, Zr-Ir) were evaluated for the simultaneous determination of arsenic, bismuth, lead, antimony, and selenium in milk by graphite furnace atomic absorption spectrometry using the 'end-capped' transversely heated graphite atomizer (THGA). Integrated platform, pretreated with Zr-Ir as permanent modifier, was elected as the optimum surface modification resulting in up to 250 firings. Two additional recoatings were possible without significant changes in the analytical performance (750 firings). For 20 μL of matrix-matched standard solutions using diluted (1:10) milk samples, typical correlation coefficients between integrated absorbance and analyte concentration (5.00-20.0 μg/L) was always better than 0.999. The levels of the analytes found in commercial milk samples were lower than the limit of detection: 2.9 μg/L As, 2.9 μg/L Bi, 1.8 μg/L Pb, 1.9 μg/L Sb, and 2.5 μg/L Se. Recoveries were found within the following intervals: 88-114% for As, 89-118% for Bi, 89-113% for Pb, 91-115% for Sb, and 92-115% for Se. The relative standard deviations (n = 12) were ≤2% (As), ≤ 5% (Bi), ≤ 1.4% (Pb), ≤ 3% (Sb), and 5% (Se), and the respective calculated characteristic masses were 54 pg As, 55 pg Bi, 40 pg Pb, 56 pg Sb, and 51 pg Se