Cloud point extraction (CPE) in association with graphite furnace atomic absorption spectrometry (GF AAS) was proposed for preconcentration and quantification of trace amounts of copper and cadmium in samples of saline produced formation water from petroleum exploration. The procedure was based on the formation of hydrophobic complexes of the analytes with 1,5-diphenylthiocarbazone (dithizone) in a micellar media of the surfactant (1,1,3,3-tetramethyl butyl) phenyl-polyethylene glycol (Triton X-114). Constrained mixture design was performed for the optimization of the proportions of the three solutions employed in the CPE: Triton X-114, dithizone, and buffer solution. Under the recommended conditions, the CPE GF AAS procedure allowed to obtain enrichment factors of 18 and 11 times, limits of quantification of 0.030 and 0.12 µg L-1 and precision, expressed as relative standard deviation (RSD, n = 8, 2.0 µg L-1), of 1.1 and 4.3% for copper and cadmium, respectively. The CPE GF AAS method was applied to the determination of copper and cadmium in samples of saline produced formation water from petroleum exploration, and its accuracy was accessed by analyzing certified reference material CASS-5 (Nearshore Seawater Reference Material for Trace Metals) from National Research Council (Canada).

Um simplex de algoritmo modificado foi utilizado na otimização de um sistema de pré-concentração para determinação de cádmio em amostras de sedimentos, cigarros e alimentos por espectrometria de absorção atômica com chama. O sistema de pré-concentração baseia-se na sorção do cádmio em uma minicoluna recheada com uma resina de Amberlite XAD-2 funcionalizada com o ácido 3,4-dihidrixibenzóico (DHB). As variáveis otimizadas foram pH e vazão da amostragem. As condições ótimas encontradas para estas variáveis foram, respectivamente: 8,7 e 8,8 mL min-1. O sistema desenvolvido apresentou fator de pré-concentração de 15,3 vezes, limite de detecção de 0,49 µg L-1, limite de quantificação de 1,65 µg L-1 e precisão expressa pelo desvio padrão relativo (%RSD, n=10) de 5,9. A exatidão do método foi determinada através da aplicação do sistema desenvolvido em material de referência certificado de sedimento de estuário (NIST 1646-1). As concentrações de cádmio encontradas nas amostras de sedimentos variaram entre 1,73 e 1,90 µg g-1. Nas amostras de cigarros os resultados obtidos foram 0,085 e 0,193 µg g-1, e nas amostras de alimentos (coentro e alface) as concentrações encontradas deste metal foram, respectivamente, 0,33 e 0,12 µg g-1.

A modified simplex algorithm was used to optimize a system of preconcentration for cadmium determination in samples of sediments, cigarettes and food using flame atomic absorption spectrometry. The preconcentration system is based on the sorption of cadmium in a minicolumn packed with Amberlite XAD-2 resin functionalized with 3,4-dihydroxybenzoic acid (DHB). The optimized variables were pH and sampling flow rate and the optimum conditions found for these variables were, respectively 8.7 and 8.8 mL min-1. The developed system showed a preconcentration factor of 15.3, detection limit of 0.49 µg L-1, quantification limit of 1.65 µg L-1 and precision expressed as relative standard deviation (% RSD, n=10) of 5.9. The accuracy of the method was checked by analysis of estuary sediment certified reference material (NIST 1646-1). The cadmium concentrations found in sediment samples ranged from 1.73 and 1.90 µg g-1. In cigarette samples the results were 0.085 and 0.193 µg g-1, and in food samples (coriander and lettuce) the concentrations found of this metal were, respectively, 0.33 and 0.12 µg g-1.

A simultaneous preconcentration method for cadmium, copper and nickel in samples of sediments and determination by inductively coupled plasma optical emission spectrometry was developed. The method is based on the extraction of the metals as complexes formed with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP) at cloud point of the nonionic surfactant polyethylene glycol tert-octylphenyl ether (triton X-114). Optimization was performed using a Doehlert design and constrained mixture design. Desirability function was used to provide a simultaneous optimization of the evaluated responses. The developed method presented limits of quantification of 0.066, 0.149 and 0.191 µg g-1 and an enrichment factor of 18.4, 16.8 and 18.2 fold for cadmium, copper and nickel, respectively. The proposed method was applied in sediment samples collected in the urban stretch of the Contas River (Jequié, BA, Brazil). Adequate accuracy was found by analysis of two certified reference materials (NIST 1646a estuarine sediments and NIST 2702 marine sediment).

In this paper, we describe the synthesis of an ion imprinted polymer (IIP) by homogeneous polymerization and its use in solid-phase to extract and preconcentrate zinc ions. Under optimal conditions (pH 5.0, preconcentration flow rate of 12.0 mL min-1, and eluted with 1.0 mol L-1 HNO3) this procedure allows the determination of zinc with an enrichment factor of 10.2, and with limits of detection and quantification of 1.5 and 5.0 µg L-1, respectively. The accuracy of our results was confirmed by analysis of tap water and certified reference materials: NIST 1570a (Spinach leaves) and NIST 1515 (Apple leaves).

Um procedimento automatizado foi desenvolvido para determinação de quantidades traços de manganês provenientes de folhas de vegetais e águas de rio utilizando espectrometria de absorção atômica com chama (FAAS) após a pré-concentração em linha deste metal usando uma minicoluna de Amberlite XAD-4 modificada com 2-aminotiofenol. O sistema de pré-concentração baseia-se na extração em fase sólida do metal na minicoluna e eluição com ácido clorídrico 0,30 mol L-1, seguido de sua determinação. As variáveis associadas ao desempenho do sistema de pré-concentração, tais como, pH, vazão de amostragem e concentração do eluente foram otimizadas utilizando um simplex básico como técnica multivariada. O método desenvolvido gerou um fator de enriquecimento de 14 vezes atingindo um limite de detecção (3 σB) de 2,0 µg L-1 e precisão expressa como desvio padrão relativo de 2,2% (%RSD, n = 10; 30,00 µg L-1). O procedimento foi aplicado para a determinação de manganês em águas de rio coletada na área urbana de Jequié/Bahia. A exatidão do procedimento foi verificada usando-se materiais de referência certificados (folhas de macieira, NIST 1515 e folhas de espinafre, NIST 1570). O procedimento desenvolvido foi aplicado para a determinação de manganês em folhas de vegetais (cebolinha, espinafre, couve-flor e repolho).

An automated procedure was developed to determine trace amounts of manganese from vegetal leaves and river waters using flame atomic absorption spectrometry (FAAS) after online preconcentration of this metal using an Amberlite XAD-4 minicolumn modified with 2-aminothiophenol. The preconcentration system is based on the solid-phase extraction of the metal into the minicolumn and elution with 0.30 mol L-1 hydrochloric acid, followed by its determination. Variables associated with the preconcentration system performance, such as pH, sampling flow rate and eluent concentration were optimized using a basic simplex as multivariate technique. The developed method provides an improvement factor of 14 along with limit of detection (3σB) of 2.0 µg L-1, and precision expressed as a 2.2% relative standard deviation (RSD%, n = 10, 30.0 µg L-1). The procedure was applied to determine manganese in river waters collected from urban area of Jequié/Bahia. The accuracy of the procedure was checked by analysis of two certified reference materials (apple leaves, NIST 1515 and spinach leaves, NIST 1570). The developed procedure has been applied for manganese determination in vegetal leaves (chive, spinach, cauliflower and cabbage).