proposto é simples, barato e altamente preciso. Neste estudo, a otimização de parâmetros experimentais que influenciam a extração, como tipo e volume dos solventes de extração e do dispersor, pH, quantidade de agente quelante e tempo de extração foi realizada normalmente usando uma abordagem passo-a-passo, na qual cada fator variou sequencialmente. O efeito dos íons interferentes na recuperação dos analitos também foi investigado. O gráfico de calibração foi linear no intervalo de 5-200 ng mL −1 , com limite de detecção de 3,4 ng mL −1. O desvio padrão relativo (RSD) foi 0,7% (n = 10, C = 2 ng mL -1 ) e o fator de enriquecimento, 28.A simple method of dispersive liquid-liquid microextraction-solidified floating organic drop (DLLME-SFO) prior to flame atomic absorption spectrometry was successfully used for separating and preconcentrating copper in human hair and tea samples. The proposed method was simple, cheap, and has high precision. In this study, optimization of experimental parameters influencing the extraction, such as type and volume of extraction and disperser solvents, pH, the amount of chelating agent and extraction time was normally carried out using a step-by-step approach, in which each factor was varied sequentially. The effect of the interfering ions on the analytes recovery was also investigated. The calibration graph was linear in the range of 5-200 ng mL . The relative standard deviation (RSD) was 0.7% (n = 10, C = 2 ng mL −1 ) and the enhancement factor was 28.Keywords: dispersive liquid-liquid microextraction, solidification, copper determination, tea and human hair analysis IntroductionTrace heavy metals are essential micro-nutrients and have a variety of biochemical functions in all living organisms. [1][2][3] Due to the positive and negative effects and the toxicity of trace heavy metals on human health and the environment, many researchers are interested in the analysis of trace metal contents of the environmental and the food samples. [4][5][6][7][8][9][10] Tea, one of the most widely consumed beverages in the world, is prepared from the young leaves of tea plants. It is considered as a healthy drink that has benefits including the prevention of many diseases. [11][12][13] Although copper is an essential trace element for humans and is an indispensable component for many enzyme systems, Cu can also act as a toxic metal to which a number of pathogenic characteristics have been attributed.14 Therefore, Cu contamination in tea leaves remains a concern, and researches should be done to ensure food safety from excessive Cu contamination.The determination of trace elements in human hair is of basic importance considering that the concentrations of these elements in hair can indicate the levels of these elements in the organism. Therefore, the determination of the metal contents in human hair can be used either as the index of the exposition for potentially toxic elements (poisoning) or as the information of the conditions of health of an individual. 15The accurate and sensitive determinations...
Um método de extração de Fe(III) em amostras de água prévio à determinação espectrométrica foi desenvolvido. Microextração dispersiva líquido-líquido (DLLME) foi usada com sucesso como método de preparação de amostras para espectrometria de absorção atômica por chama (FAAS). Na abordagem proposta, 8-hidroxiquinolina (oxina) foi usada como agente quelante, clorofórmio e metanol foram selecionados como solventes extrator e dispersivo, respectivamente. Alguns fatores influenciando a eficiência da extração de Fe(III) e sua subsequente determinação foram estudados e otimizados, incluindo: tipo e volume de solventes extrator e dispersor, pH da solução da amostra, concentração do agente quelante e tempo de extração. Nas condições otimizadas, o fator de enriquecimento deste método para Fe(III) foi 462. O limite de detecção para Fe(III) foi 4,5 ng mL -1 , e o desvio padrão relativo (RSD) 1,4% (n = 5, c = 400 ng mL -1).An extraction method for Fe(III) from water sample before spectrometric determination was developed. Dispersive liquid-liquid microextraction (DLLME) technique was successfully used as sample preparation method for flame atomic absorption spectrometry (FAAS). In the proposed approach, 8-hydroxy quinoline (oxine) was used as chelating agent, chloroform and methanol were selected as extraction and dispersive solvents, respectively. Some factors influencing the extraction efficiency of Fe(III) and its subsequent determination were studied and optimized, including: type and volume of extraction and dispersive solvents, pH of sample solution, concentration of the chelating agent and extraction time. Under the optimized conditions, the enrichment factor of this method for Fe(III) was 462. The limit of detection for Fe(III) was 4.5 ng mL -1 , and the relative standard deviation (RSD) 1.4% (n = 5, c = 400 ng mL -1 ).
In this work, zinc oxide/polypyrrole nanocomposite coating was fabricated on stainless steel and evaluated as a novel headspace solid-phase microextraction fiber coating for extraction of ultra-trace amounts of environmental pollutants, namely, phthalate esters, in water samples. The fiber nanocomposite were prepared by a two-step process including the electrochemical deposition of polypyrrole on the surface of stainless steel in the first step, and electrochemical deposition of zinc oxide nanosheets in the second step. Porous structure together with zinc oxide nanosheets with the average diameter of 30 nm were observed on the surface by using scanning electron microscopy. The effective parameters on extraction of phthalate esters (i.e., extraction temperature, extraction time, desorption temperature, desorption time, salt concentration, and stirring rate) were investigated and optimized by one-variable-at-a-time method. Under optimized conditions (extraction temperature, 90°C; extraction time, 40 min; desorption temperature, 270°C; desorption time, 5 min; salt concentration, 25% w/v; and stirring rate, 1000 rpm), the limits of detection were in the range of 0.05-0.8 μg/L, and the repeatability and fiber-to-fiber reproducibility were in the ranges of 6.1-7.3% and 8.7-10.2%, respectively.
In this study, a method of dispersive liquid phase microextraction combined with the flame atomic absorption spectrometry was proposed for the determination of trace Hg using diphenylthiocarbazone as chelating reagent. Several factors which have effect on the microextraction efficiency of Hg, such as pH, extraction and dispersive solvent type and their volume, concentration of the chelating agent, extraction time were investigated, and the optimized experimental conditions were established. After extraction, the enrichment factor was 68. The detection limit of the method was 45 ng mL -1 , and the relative standard deviation for eight determinations of 2 µg mL -1 Hg was 1.7%. The results for the determination of Hg in environmental water samples (tap water, well water, mineral water and Caspian sea water) have demonstrated the applicability of the proposed method.
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