In the present work, a novel, simple, and efficient method for the determination of silver in natural water samples was developed. The method is based on the extraction of silver with coacervate made up of decanoic acid reverse micelles and the subsequent determination by flame atomic absorption spectrometry (FAAS). Dithizone was used as a chelating agent. To obtain the best extraction results, some experimental parameters (such as coacervate composition, pH, concentration of chelating agent, and ionic strength) affecting the extraction efficiency were investigated and optimized. Under optimum conditions, the calibration curve was linear in the concentration range of 5-200 µg L-1, with the correlation coefficient (r) equal to 0.995. The limit of detection and the enrichment factor were 1.6 µg L-1 and 15, respectively. The method was successfully applied to the analysis of silver in natural water samples.

<p>This paper describes a new approach for the preconcentration of lead (Pb²⁺) by solventassisted dispersive solid phase extraction (SADSPE) prior to analyzing by flame atomic absorption spectrometry (FAAS). In this method, the dispersion of the sorbent was achieved by injecting a solution of the sorbent into the aqueous sample. Thereby, a cloudy solution formed. The cloudy state resulted from the dispersion of the fine particles of the sorbent in the bulk aqueous sample. Pb ions reacted with 1-(2-pyridylazo)-2-naphthole (PAN) as chelating agent to form a hydrophobic complex. After extraction, phase separation was performed by centrifugation and as a result, the enriched analyte in this demented phase could be determined by FAAS. Some parameters that influenced solvent-assisted dispersive solid phase extraction and subsequent determination were evaluated in detail. Under optimized conditions (pH 9, PAN concentration: 1.0 × 10^-3 mol L^-1, sorbent: 0.1% m/v 1,4-dichlorobenzene, disperser solvent: 0.5 mL ethanol), a preconcentration factor of 50 could be obtained, and the limit of detection (LOD) for lead was 1.3 μg L^-1. Relative standard deviation for ten replicate determinations of the standard solution containing 20 μg L^-1 lead was 5.0%. The proposed method was successfully applied for the determination of lead in water samples with satisfactory results.</p>

Um procedimento de extração no ponto nuvem de sinergia rápida foi desenvolvido para a separação e determinação de traços de chumbo em amostras de água e de alimentos antes da determinação por espectrometria de absorção atômica com chama (FAAS). A extração no ponto nuvem de sinergia rápida (RS-CPE) simplifica e acelera de forma eficiente o procedimento tradicional de extração no ponto nuvem (CPE). Este método é realizado em 1 minuto, a temperatura ambiente, na presença do surfactante não-iônico Triton X-114. Octanol atuou como reagente sinérgico para a extração no ponto nuvem, causando a diminuição na temperatura do Triton X-100, e contribuiu para o subsequente processo de extração. Alguns parâmetros que afetam a extração no ponto nuvem e a determinação do chumbo foram avaliados cuidadosamente, como o pH da amostra, a quantidade de octanol, a quantidade de Triton X-114, o tipo de solvente para a extração e a força iônica, bem como o efeito de interferentes. Nas condições otimizadas para a extração de chumbo (pH 8.5; octanol: 10 µL; Triton X-114: 0,04% w/v; e solvente de diluição: HNO3 1 mol L-1 na presença de metanol) foi obtido um fator de enriquecimento igual a 40 e limite de detecção (LOD) de 1,6 µg L-1. O desvio padrão para dez replicatas de uma solução contendo 100 µg L-1 de chumbo foi de 2,1%. O método proposto foi aplicado para a determinação de chumbo em amostras de água e de alimentos (espinafre, arroz e chá preto), com resultados satisfatórios.

A simple rapidly synergistic cloud point extraction procedure has been developed for the separation and preconcentration of trace amounts of lead from food and water samples by flame atomic absorption spectrometry (FAAS). Rapidly synergistic cloud point extraction (RS-CPE) greatly simplified and accelerated the procedure of traditional cloud point extraction (CPE). This method was accomplished in room temperature in 1 min. Non-ionic surfactant Triton X-114 was used as extractant. Octanol worked as cloud point revulsant and synergic reagent which lowered the cloud point temperature of Triton X-114 and assisted the subsequent extraction process. Some parameters that influenced cloud point extraction and subsequent determination were evaluated in detail, such as sample pH, amounts of octanol, amounts of Triton X-114, type of diluting solvent, extraction time and ionic strength, as well as interferences. Under optimized conditions (pH 8.5, octanol: 10 µL, Triton X-114: 0.04% w/v and diluting solvent: 1 mol L-1 HNO3 in methanol), an enhancement factor of 40 could be obtained, and the detection limit (LOD) for lead was 1.6 µg L-1. Relative standard deviation for ten replicate determinations of the standard solution containing 100 µg L-1 lead was 2.1%. The proposed method was applied for the determination of lead in food (spinach, rice and black tea bag) and water samples and satisfactory results were obtained.