Pré-concentração de chumbo e cádmio em um sistema de micro extração líquido-líquido e determinação por espectrometria de absorção atômica com chama

Abstract

lead and cadmium in aqueous samples using solvent microextraction and dithizone as complexing agent with FAAS was developed. Solvent microextraction parameters were optimized. The effect of foreign ions on the extraction yields was studied. The extraction was carried out until the aqueous to organic phase ratio achieved a 250 fold preconcentration of metals. For preconcentration times of 4 min the 3s detection limits, relative standard deviations (n=7) and linear calibration ranges were 1.6 mg L -1 , 5.8% and 10.0 -80.0 mg L -1 for lead and 11.1 ng L -1 , 5.9% and 0.3 -3.0 mg L -1 for cadmium, respectively. The solvent microextraction procedure presented here was applied to the determination of lead and cadmium in natural waters.Keywords: preconcentration; dithizone; flame atomic absorption spectrometry; natural waters. INTRODUÇÃOEmbora o desenvolvimento da instrumentação tenha possibilitado avanços em muitos aspectos da Química Analítica, em muitos casos a instrumentação disponível não apresenta sensibilidade analí-tica suficiente para a determinação de traços. Além disso, é comum não se analisar quimicamente amostras em sua forma original (aquosa ou sólida), pois elas podem conter espécies interferentes e serem incompatíveis com os equipamentos analíticos. Para contornar tais problemas são empregados procedimentos de preparo da amostra, os quais incluem várias etapas: coleta, armazenagem, solubilização, extração, pré-concentração, isolamento dos compostos de interesse e análise qualitativa e quantitativa. As etapas de extração e pré-concentração dos analitos são ainda o "calcanhar de Aquiles" de todo o procedimento analítico devido ao fato dessas etapas serem lentas, apresentarem a possibilidade de contaminação e a perda das espé-cies de interesse durante o manuseio da amostra. Assim, o desenvolvimento de procedimentos para a separação e pré-concentração de contaminantes de matrizes ambientais têm sido propostos, como por exemplo, extração líquido-líquido 1-4 , co-precipitação 5

Magnetic Solid-Phase Microextraction for Lead Detection in Aqueous Samples Using Magnetite Nanoparticles

“…Compared to other extraction and preconcentration methods such as those developed by Baghban et al 23 and Carasek, 24 who presented LOD values of 100 and 10 µg L -1 , respectively, the proposed methodology is efficient.…”

Influence of transcutaneous electrical stimulation on heterotopic ossification: an experimental study in Wistar rats

“…The analysis was performed to measure the calcium levels in the left quadriceps with a Spectr AA 250 Plus (Varian, USA) flame spectrophotometer. Before analysis, the sample was subjected to a liquefaction process ( 21 , 22 ) in order to produce a homogeneous sample of biological material. The spectrophotometer was calibrated, using the most intense emission line of calcium at 422.7 nm.…”

Determination of Trace Amount of Lead (11) and Cadmium (11) Ions in Real Water and Real Samples by Flame Atomic Absorption Spectrometry After Cloud Point Extraction Using Selective Synthesis Ligand2-(3- indolyl) – 4,5 di phynyl imidazole

“…However, the detection limit for measurement of low levels of cadmium and lead ions in samples is not suitable, therefore the preconcentration before measurement with flame atomic absorption spectrometry is necessary. The old methods of separating for example a liquidliquid extraction are used toxic organic solvents which are dangerous to the environment and humans [18][19][20].…”