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Moraes D.P.,Academy of Sciences of the Czech Republic | Moraes D.P.,Federal University of Rio Grande do Sul | Svoboda M.,Academy of Sciences of the Czech Republic | Matousek T.,Academy of Sciences of the Czech Republic | And 3 more authors.
Journal of Analytical Atomic Spectrometry | Year: 2012

Hydride generation-cryotrapping-gas chromatography-atomic absorption spectrometry (HG-CT-AAS) was applied for arsenic speciation analysis in an injectable drug, N-methylglucamine antimonate. The method employs generation of substituted hydrides and selective hydride generation, which makes possible an analysis of arsenites and arsenates and their mono-, di-, and trimethyl substituted species. Interference of the antimony matrix was eliminated using the T-valve to prevent supply of the stibine interferent to the atomizer. The limits of detection in measured sample solutions were 70 ng L -1 for inorganic arsenate, 42 ng L -1 for mono- and dimethylarsenates and 30 ng L -1 for all the other determined species. Concentrations of all methylated species in all samples were below their detection limits. A significant but different amount of inorganic As was found in different batches of the drug: between 0.9 and 2.3 mg L -1 with 7% to 10% of the content present as the trivalent form. The accuracy was assessed by the comparison of the determined inorganic arsenic content with the total arsenic content determined by the conventional inductively coupled plasma mass spectrometry. Both methods yielded for individual samples equal values within experimental error. The HG-CT-AAS procedure showed good performance with minimum sample pretreatment at low investment and running costs. © 2012 The Royal Society of Chemistry. Source


Pereira J.S.F.,Federal University of Santa Maria | Pereira J.S.F.,Instituto Nacional Of Ciencia E Tecnologia Bioanalitica | Moreira C.M.,Federal University of Santa Maria | Moreira C.M.,Instituto Nacional Of Ciencia E Tecnologia Bioanalitica | And 4 more authors.
Chemosphere | Year: 2011

Chemically chlorinated organic matter as well as natural background humic acids contain significant amounts of organically bound halogens that must be determined for assessment of environmental pollution. In this work the use of ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS) is proposed for the determination of total organic Cl, Br and I concentration in humic acids extracted from various forest soil horizons after a single digestion by microwave-induced combustion (MIC). Samples were pressed as pellets and combusted using 20bar of oxygen and ammonium nitrate solution as igniter. Analytes were absorbed in diluted alkaline solution (50mM (NH 4) 2CO 3) and a reflux step was applied after combustion to improve analyte recoveries (5min, microwave power of 1400W). The accuracy was evaluated using certified reference materials (CRM) and spiked samples. Using MIC the agreement with CRM values and spike recoveries was higher than 97% for all analytes. As an advantage over conventional procedures, using MIC it was possible to digest up to eight samples in only 25min, obtaining a single solution suitable for all halogens determination in humic acids samples by different techniques (IC and ICP-MS). The limit of detection (3σ) for Cl, Br and I obtained by IC was 1.2, 2.5 and 4.3μgg -1 and by ICP-MS it was 1.4, 0.03 and 0.002μgg -1, respectively. © 2011 Elsevier Ltd. Source


Pereira J.S.F.,Federal University of Santa Maria | Pereira J.S.F.,Instituto Nacional Of Ciencia E Tecnologia Bioanalitica | Moraes D.P.,Federal University of Santa Maria | Moraes D.P.,Instituto Nacional Of Ciencia E Tecnologia Bioanalitica | And 11 more authors.
Microchemical Journal | Year: 2010

A method for light and heavy crude oil digestion using microwave-induced combustion (MIC) in closed vessels is described for further determination of Ag, As, Ba, Bi, Ca, Cd, Cr, Fe, K, Mg, Li, Mn, Mo, Ni, Pb, Rb, Se, Sr, Tl, V, and Zn by inductively coupled plasma mass spectrometry (ICP-MS). Conventional microwave-assisted acid digestion (MW-AD) in pressurized vessels and analyte determination by inductively coupled plasma optical emission spectrometry (ICP OES) were also used for results comparison. For MIC procedure, samples were wrapped in polyethylene films and combusted using 20bar of oxygen and 50μl of 6moll-1 ammonium nitrate as aid for ignition. The concentration of nitric acid used as absorbing solution was evaluated (1, 2, 4, 7, 10 and 14moll-1) using an additional reflux step after combustion. Accuracy was evaluated for As, Ba, Ni, Se V, and Zn using certified reference material (CRM) with similar matrix composition and for Cr, Fe, K, Mg, Mn, and Mo by neutron activation analysis (NAA). Recovery tests were also performed for all the analytes by MIC and they were better than 97% using 2moll-1 nitric acid as absorbing solution (with reflux step). Agreement with certified values and NAA results was better than 95%. Using MIC it was possible to obtain lower limits of detection (LODs) by ICP-MS and also by ICP OES in comparison with those obtained by MW-AD. In spite of both sample preparation techniques were apparently suitable for crude oil digestion, MIC was preferable in view of the possibility of using diluted nitric acid as absorbing solution that is an important aspect to minimize interferences by ICP-MS and ICP OES. In order to avoid polyatomic interferences on 52Cr and 56Fe determinations by ICP-MS, a dynamic reaction cell with ammonia gas was used. Residual carbon content in digests obtained by MW-AD and MIC was 15% and <1%, respectively. Using MIC the simultaneous digestion of 8 samples was possible in less than 30min. © 2010 Elsevier B.V. Source


Pereira J.S.F.,Federal University of Santa Maria | Pereira J.S.F.,Instituto Nacional Of Ciencia E Tecnologia Bioanalitica | Antes F.G.,Federal University of Santa Maria | Antes F.G.,Instituto Nacional Of Ciencia E Tecnologia Bioanalitica | And 9 more authors.
Journal of Analytical Atomic Spectrometry | Year: 2010

A procedure for single and multi-walled carbon nanotubes digestion by microwave-induced combustion (MIC) is proposed for the first time for further halogens (Cl, Br and I) determination by inductively coupled plasma mass spectrometry (ICPMS) and ion chromatography (F, C, Br and I). Samples of carbon nanotubes (up to 500 mg) were pressed as pellets and combusted using 20 bar of oxygen and 50 μl of 6 mol l-1 of ammonium nitrate as igniter. The following absorbing solutions were evaluated: H2O, (NH 4)2CO3, NH4OH, tetramethylammonium hydroxide (TMAH) and water-soluble tertiary amines (CFA-C). A reflux step was applied after combustion (5 min of microwave irradiation at 1400 W) in order to achieve better analyte recoveries. For Cl determination by ICPMS, a dynamic reaction cell was used with ammonia as reaction gas. The accuracy was evaluated using certified reference materials (CRM) of coal, spiked samples and also by comparison of results with neutron activation analysis. In spite of 1% (v/v) of TMAH or CFA-C being used as absorbing solution, 100 mmol l-1 NH 4OH was preferred in view of lower blank values and quantitative recoveries (better than 97%). Agreement with CRM values for NIST 1632b, NIST 1632c and SARM 19 was higher than 96% for Cl and Br (ICPMS) and for F (IC). The limit of detection (LOD, 3σ) for Cl, Br and I obtained by ICPMS was 1.3, 0.02 and 0.002 μg g-1, respectively. The LOD for F, Cl, Br and I determined by IC was 0.3, 1.1, 2.4 and 4.2 μg g-1, respectively. The residual carbon content for MIC digests was always below 1%. As an advantage over conventional procedures, using MIC it was possible to digest up to eight samples in only 25 min, obtaining a single solution suitable for determination of all halogens by different techniques. According to the authors' knowledge this is the first application for halogen determination in this kind of material. © The Royal Society of Chemistry 2010. Source

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