Homogeneous liquid-liquid microextraction via flotation assistance (HLLME-FA) was investigated for the extraction of molybdenum from the water samples. Alizarin Red S and cetyl trimethylammonium bromide (CTAB) were used as a complexing ligand and ion-pairing reagent, respectively. The enriched analyte in the floated organic phase was determined by electrothermal atomic absorption spectrometry (ETAAS). In this work, low density organic solvent was used and no centrifugation was required in this procedure. A special extraction cell was designed to facilitate the collection of the low-density extraction solvent. By using air flotation, the organic solvent was collected at the conical part of the designed cell. Under the optimum conditions, the method performance was studied in terms of linear dynamic range (0.5-200 µg L-1), linearity (r2 > 0.991), precision (repeatability < 10.0 %). Also, the limit of detection (LOD) of 0.1 µg L-1 was obtained for molybdenum. The proposed method has been successfully applied for the determination of the molybdenum in water samples.

A determinação de chumbo e cádmio por espectrometria de absorção atômica de chama após a extração de fase sólida do óxido de grafeno (GO) utilizando o 4-acetamidotiofenol (ATP) como reagente quelante foi descrita. PM6 semi-empírico e a teoria de densidade funcional PBE foram os métodos usados na investigação do mecanismo de adsorção dos complexos em folhas de GO. Os principais fatores que influenciam a pré-concentração e determinação de analitos (pH, quantidade de ATP, tipo e concentração de eluente, fluxo e volume de amostra) foram examinados em detalhe. O efeito de íons interferentes no fator separação-pré-concentração também foi investigado. Para soluções de Pb(II) e Cd(II) 1,0 µg L-1, o fator de pré-concentração chegou a 250 (em condições otimizadas). Os limites de detecção para Pb(II) e Cd(II) foram 170 e 80 ng L-1, respectivamente. A validade do método proposto foi checada com materiais de referência padrão e foi aplicado com sucesso na determinacao de traços de Pb(II) e Cd(II) em amostras de água, ervas e peixe com recuperação de 99,4-103,5%.

The determination of lead and cadmium by flame atomic absorption spectrometry after solid phase extraction on graphene oxide column with use of 4-acetamidothiophenol (ATP) as chelating reagent was described. PM6 semi-empirical and PBE density functional theory methods were used to investigation of adsorption mechanism of the complexes on GO sheet. The main factors influencing the preconcentration and determination of the analytes (pH, ATP amount, eluent type and concentration, flow rate and sample volume) were examined in detail. The effect of interfering ions on the separation-preconcentration of analytes was also investigated. For Pb(II) and Cd(II) solutions of 1.0 µg L-1, the preconcentration factor was as high as 250 (under the optimized conditions). The detection limits for Pb(II) and Cd(II) were 170 and 80 ng L-1, respectively. The validity of the proposed method was checked with standard reference materials and it has been successfully applied for the determination of trace Pb(II) and Cd(II) in water, herbal and fish samples with the recoveries of 99.4-103.5%.