A new analytical protocol has been developed for the determination of mercury in surface sediments using dithiothreitol (DTT) as a new chelating reagent for the extraction. This protocol requires a small sample mass (250 mg), 4.0 mL of a 0.1 M (pH = 9.0) aqueous DTT solution, and sonication for 30 min, followed by cold vapor atomic fluorescence spectrometry (CV-AFS). The limits of detection and quantification determined were 6 and 18 ng g−1, respectively. The method was validated using three standard reference materials, SRM NIST 1646a, PACS-2, and MESS-3, with recoveries in the range of 102-124%. The new analytical protocol was successfully applied in riverine surface sediments, revealing concentrations in the range of 220-340 ng g−1. The results obtained by CV-AFS were compared to those obtained by DMA-80 (direct mercury analyzer). The linear regression equation obtained was [CV-AFS] = (0.91 ± 0.07)[DMA-80] + (0.04 ± 0.02), revealing no systematic difference between the analytical methods. Hence, the proposed method does not require the complete digestion of the sediment, and was found to be comprehensive, simple, accurate and suitable to be employed for determination of mercury in sediment samples.

This study proposes an optimized procedure for the determination of inorganic antimony species in natural waters using hydride generation atomic fluorescence spectrometry (HG AFS) and continuous flow system. The variables of the hydride generation system, such as pre-reduction time, hydrochloric acid concentration and sodium tetrahydroborate concentration, were evaluated using full factorial design at two levels and Doehlert design. After optimized experimental conditions, the method allowed the determination of antimony with limits of detection and quantification of 9 and 30 ng L-1, respectively. The precision (RSD) of the method was < 5% and the accuracy was confirmed by the analysis of certified reference material (SLRS-4, River water for trace metals). The method was successfully applied for inorganic antimony speciation in water samples collected in Salvador City, Bahia State, Brazil. In mineral water, total Sb concentrations ranged from 0.26 to 0.30 µg L-1, whereas the concentrations of SbIII were below 0.03 µg L-1. On the other hand, in natural surface waters, the quantifiable concentration of total Sb and SbIII ranged from 0.41 to 1.23 µg L-1 and 0.23 to 1.04 µg L-1, respectively. The highest average concentrations of Sb were obtained in regions with the largest urban influence, ratifying the anthropogenic impact in water bodies.

In this study, the elemental composition of nine medicinal plants and phytomedicines was evaluated by using axial view inductively coupled plasma optical emission spectrometry (ICP OES) after three digestion procedures: dry ashing (DA) and two wet digestions with a mineral acid (HNO3/H2O2) mixture on a conventional hot plate (CD), besides microwave digestion (MW). Accuracy was assessed from spinach leaves (CRM 1570a) and recovery values were in the range of 82 to 113.8%. Precisions, such as relative standard deviation (RSD), below 10% were reached. The MW procedure was preferred for its accuracy (recovery values of 94 to 102%), reduced contamination, increase in the efficiency of the decomposition process, lower residual acidity and reduced time required for digestion. The concentrations of analytes in the samples (minimum-maximum in μg g-1) were: Ca (100.71-462.20), Co (0.54-0.85), Cu (0.32-7.82), Fe (2.74-18.03), Mg (18.40-521.28), Mn (0.17-55.14), Ni (0.56-1.25) and Zn (2.96-20.92). The levels of Al, Ba, Cd, Cr, Mo, Pb, Se and V in all investigated samples were found to be below the limit of detection of ICP OES. The multielement analysis by ICP OES showed that the method is simple, fast and reliable for the multielement determination in medicinal plants and phytomedicines.

Carbon black (CB) grafted with 3-mercaptopropyltrimethoxysilane (3-MPTMS) was used as solid phase extractor for Cd2+ in a flow injection system coupled to flame atomic absorption spectrometry (FAAS). The influence of pH, buffer concentration, preconcentration flow rate and eluent concentration on preconcentration of Cd2+ were investigated by means of chemometric tools. The characterization of the adsorbent chemically modified was performed by Fourier transform infrared, scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis, Raman spectroscopy and textural analysis. To perform the on-line preconcentration, 20.0 mL of a pH 7.0 Cd2+ solution at a flow rate of 4.0 mL min−1 was loaded through 30.0 mg of modified CB and then eluted with 1.0 mol L−1 HCl toward the FAAS instrument. The limits of detection and quantification were found to be 0.20 and 0.66 µg L−1, respectively. Addition and recovery tests carried out in real samples (mineral, tap and saline waters, and cigarette sample) and the analysis of certified reference material (TORT-2, lobster hepatopancreas reference) attested the applicability of proposed method.

O presente trabalho descreve a otimização e validação de um método para determinação direta de cádmio em amostras de vinho por espectrometria de absorção atômica com atomização eletrotérmica (ET AAS). A otimização foi realizada empregando um planejamento fatorial completo de 2 níveis, incluindo os fatores: tempo (10 s) e temperatura de pirólise (600 ºC), temperatura de atomização (1300 ºC) e massa de modificador (15 µg). Sob as condições otimizadas, foi encontrada uma massa característica de 0,7 pg, limite de detecção e quantificação de 0,030 e 0,100 µg L-1, respectivamente, para um volume de amostra de 20 µL. A precisão foi de 0,30, 0,37 e 0,49% (RSD) para amostras de vinho com concentrações de 1,286, 0,266 e 0.356 µg L-1, respectivamente. A exatidão da metodologia de determinação direta empregando ET AAS foi avaliada por comparação usando um método de digestão ácida e determinação também por ET AAS para cinco amostras de vinho. O método foi aplicado para determinação de cádmio em 30 amostras de vinhos brasileiros. A concentração de cádmio variou de 0,146 a 1,563 µg L-1, cujos valores estão abaixo do nível máximo permitido pela Organização Internacional de Vinha e Vinho (OIV) e pela legislação brasileira, 10 µg L-1.

This work describes the optimization and validation of a direct method employing electrothermal atomic absorption spectrometry (ET AAS) for the determination of cadmium in wine. The optimization step was carried out using a two-level full factorial design, involving the followings factors: pyrolysis time (10 s) and temperature (600 ºC), atomization temperature (1300 ºC) and modifier mass (15 µg). Under the optimized conditions, a characteristic mass of 0.7 pg and limits of detection and quantification of 0.030 and 0.100 µg L-1, respectively, were obtained using a sample volume of 20 µL. The precision expressed as relative standard deviation (RSD %) was 0.30, 0.37 and 0.49% for wines with cadmium concentrations of 1.286, 0.266 and 0.356 µg L-1, respectively. The accuracy of the new direct determination methodology applying ET AAS was assessed by comparison with an acid digestion methodology, also with determination by ET AAS, using five wine samples. The proposed method was applied for the determination of cadmium in 30 Brazilian wine samples. The cadmium content varied from 0.146 to 1.563 µg L-1; all these values are lower than the permissible maximum level stipulated by the International Organization of Vine and Wine (OIV) and also by Brazilian legislation, which is 10 µg L-1.

Um sistema contendo Amberlite XAD - 2 (estireno-divinilbenzeno) carregado com 2-(2-tiazolilazo)-5-dimetilaminfenol (TAM) é proposto para amostragem em campo, preconcentração e determinação de cádmio (II) e níquel (II) em amostras de águas naturais usando espectrometria de absorção atômica com chama (FAAS). O processo de otimização foi univariado e os seguintes parâmetros foram estudados: efeito de pH, efeito de vazão de amostragem, concentração da solução e vazão de eluente, efeito de outros ions, precisão e exatidão. Na etapa de amostragem, os ions metálicos são retidos na minicoluna sob a forma de TAM complexos. A amostra é percolada com vazão de 3,0 mL min-1 após filtração usando filtro de 0,45 µm. Posteriormente, a minicoluna é incorporada sobre um sistema em fluxo contínuo e os ions metálicos são eluídos com solução de ácido clorídrico de concentração 1,0 mol L-1 diretamente para o sistema de nebulização do espectrômetro. Para níquel, os limites de detecção (LOD) e quantificação (LOQ) foram 12 e 39 ng L -1, respectivamente. A precisão expressa como desvio padrão relativo (RSD) para 10 determinações independentes foram 5,5% e 7,0% para concentrações de níquel de 10 e 1,0 µg L-1, respectivamente. O fator de preconcentração, calculado como a relação entre as inclinações de curvas obtidas pelo presente procedimento e pela aspiração direta foi 637 para um volume de amostra de 150 mL. Para cádmio, os LOD e LOQ foram 22 e 72 ng L-1, respectivamente. A precisão expressa como RSD, foi 6,0% e 6,8% para concentrações de cádmio de 10 e 1,0 µg L-1, respectivamente. O fator de preconcentração experimental foi 548, também para um volume de amostra de 150 mL. O procedimento foi aplicado para determinação de cádmio e níquel em águas naturais de baixa salinidade, coletadas de lagoas da Cidade de Salvador, Bahia, Brasil.

A system containing Amberlite XAD - 2 (styrene-divinylbenzene copolymers) loaded with 2-(2thiazolylazo)-5-dimethylaminophenol (TAM) reagent is proposed for field sampling, preconcentration and determination of cadmium (II) and nickel (II) ions in fresh water using flame atomic absorption spectrometry (FAAS). The optimisation process was univariate and the followings parameters were studied: pH effect, effect of sample flow rate, eluent concentration and flow rate, effect of other ions, precision and accuracy as recovery tests. In the sampling step, metal ions are retained in a minicolumn as TAM complexes. The sample is pumped at 3.0 mL min-1 with on-line filtration using a 0.45 µm filter. Afterwards, the minicolumn is incorporated in a flow-injection system and the metal ions eluted with a solution of 1.0 mol L-1 hydrochloric acid into the nebuliser-burner system of the spectrometer. For nickel, the limits of detection (LOD) and quantification (LOQ) were 12 and 39 ng L -1, respectively. The precision expressed as relative standard deviation (RSD) for ten independent determinations was 5.5% and 7.0% for nickel concentrations of 10 and 1.0 µg L-1, respectively. The experimental preconcentration factor, calculated as the ratio of the slopes of the calibration curves obtained by the present procedure and manual direct aspiration was 637 for a sample volume of 150 mL. For cadmium, the LOD and LOQ are 22 ng L-1 and 72 ng L-1, respectively. The precision, expressed as RSD was 6.0% and 6.8% for cadmium concentrations of 10 and 1.0 µg L-1, respectively. The experimental preconcentration factor was 548 also for a sample volume of 150 mL. The procedure was applied for determination of cadmium and nickel in fresh water samples with low saline concentration, collected in lagoons from Salvador City, Bahia, Brazil.