A new, simple, rapid and efficient solvent terminated-auxiliary solvent-dispersive liquid-liquid microextraction (ST-AS-DLLME) technique for determination of cyanide ions by microvolume UV-Vis spectrophotometry was developed. Effective parameters on the extraction and absorbance of cyanide were optimized using two optimization methods: fractional factorial design (FFD) and central composite design (CCD). Zinc(II) tetraphenylporphyrine (ZnTPP) was used as a selective cyanide receptor agent. Methyl isobutyl ketone (MIBK), ethanol and 1-butanol were used as extraction solvent, dispersive solvent and demulsifier solvent, respectively. The method shows very good selectivity in presence of other species. The analytical curve was linear in the range of 4.0-130 µg L-1 with a limit of detection of 1.0 µg L-1. Relative standard deviation (RSD) of the method for ten replicate measurements of 100 µg L-1 of cyanide was 1.1%. The method was successfully applied for determination of cyanide in natural water and plasma samples with good spike recoveries.

Um procedimento de extração em fase líquida miniaturizado, baseado na microextração direta em gota suspensa combinada com espectrometria de absorção atômica com chama foi desenvolvido para a determinação de traços de ferro e cobre, sem a necessidade da etapa de centrifugação para a separação de fases. O método consiste na extração de complexos de ferro e cobre com 2-mercaptopiridina-N-óxido em uma microgota de metil-isobutil-cetona (MIBK) como solvente extrator. Os fatores que afetam a extração foram otimizados. Nas condições otimizadas um fator de enriquecimento de ~25 foi obtido para ambos, ferro e cobre, a partir de 6,5 mL de fase aquosa. As curvas analíticas mostraram-se lineares no intervalo de 40 a 800 µg L-1 e de 25 a 1200 µg L-1 para ferro e cobre, respectivamente. Os limites de detecção foram 3,76 e 1,84 µg L-1 para ferro e cobre, respectivamente. O método proposto foi aplicado para a determinação de íons ferro e cobre em águas, frutas, vegetais e também em materiais de referência certificados, com resultados bastante eficientes.

A miniaturized liquid-phase extraction procedure based on directly suspended droplet microextraction combined with flame atomic absorption spectrometry was developed for determination of trace amounts of iron and copper, without any need for the centrifugation step for phase separation. The method was based on the extraction of the iron and copper complexes with 2-mercaptopyridine-N-oxide onto a microdrop of methyl isobutyl ketone (MIBK) as extractant solvent. The factors influencing the extraction were optimized. Under optimum conditions, an enrichment factor of ~25 was obtained for both iron and copper from only 6.5 mL of aqueous phase. The analytical curves were linear between 40-800 μg L-1 and 25-1200 μg L-1 for iron and copper, respectively. The limits of detection were 3.76 μg L-1and 1.84 μg L-1 for iron and copper, respectively. The developed method has been successfully applied for the determination of iron and copper ions in environmental waters, fruits, vegetables and also certified reference materials, with high efficiency.

Um método de extração de fase sólida baseado em nanopartículas magnéticas de óxido de ferro (MIONPs) modificadas por dodecyl sulfato de sódio (SDS) foi desenvolvido para a preconcentração e a determinação de traços de íons urânio (VI). Oxina (8-quinolinol) foi usada como agente quelante e os fatores que afetam a formação do complexo e a extração de urânio foram otimizados. Etanol contendo 1% (v v-1) NH3 foi usado como desorvente e a absorvância do eluente foi medida em 370 nm por espectrofotometria UV-Vis. A curva analítica foi linear na faixa de 3,0-300 µg L-1 com um limite de detecção de 0,8 µg L-1. O método foi aplicado com sucesso para a determinação de urânio em água de torneira, água mineral, água de rio e amostras de água de mar com recuperações variando de 93-108%. Este método também foi aplicado para a determinação de urânio (VI) em amostras de rocha e amostras biológicas e os resultados obtidos concordaram com aqueles obtidos por ICP-MS e GF AAS.

A solid phase extraction method based on magnetic iron oxide nanoparticles (MIONPs) modified by sodium dodecyl sulfate (SDS) was developed for the preconcentration and determination of trace amounts of uranium(VI) ions. Oxine (8-quinolinol) was used as chelating agent and the factors influencing the complex formation and extraction of uranium were optimized. Ethanol containing 1% (v v-1) NH3 was used as desorbing agent and the absorbance of eluent was measured at 370 nm by UV-Vis spectrophotometry. The analytical curve was linear in the range of 3.0-300 µg L-1 with a limit of detection of 0.8 µg L-1. The method was successfully applied for the determination of uranium in tap water, mineral water, river water and sea water samples with spike recoveries ranging 93-108%. This method was also applied for the determination of uranium(VI) in rock and biological samples and the obtained results were in accordance with inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (GF AAS) methods.

A new sensitive and selective procedure for speciation of trace dissolved Fe(III) and Fe(II), using modified octadecyl silica membrane disks and determination by flame atomic absorption spectrometry was developed. A ML3 complex is formed between the ligand and Fe(III) responsible for extraction of metal ion on the disk. Various factors influencing the separation of iron were investigated and the optimized operation conditions were established. Under optimum conditions, an enrichment factor of 166 was obtained for Fe3+ ions. The calibration graph using the preconcentration system for Fe3+ was linear between 40.0 and 1000.0 μg L-1.