Use of fiberglass support in the application of dried-spot technique with dispersion liquid-liquid microextraction for the determination of Co, Cr, Cu, Ni and Pb by Energy Dispersive X-Ray Fluorescence Spectrometry

摘要

Contamination of environmental matrices with toxic metals is a serious problem. It is important to determine the concentration of such metals, particularly in agricultural soils, due to their negative impact on human life. This work aimed to determine a more adequate solid support and better operating conditions in the application of dried-spot technique on dispersion liquid-liquid microextraction (DLLME) for determine of cobalt, lead, chromium, copper, and nickel by applying Energy Dispersive X-ray Fluorescence Spectrometry (EDXRF). The solid supports studied were qualitative and quantitative filter paper, cellulose ester membrane and glass fiber. The parameters for DLLME, such as pH and volumes of solvent dispersive and extractor, were evaluated and optimized to reduce the limit of detection for the analytical method. A fiberglass backing had a superior result compared to another substrate to add the preconcentrated rich phase. Preconcentration factors were 58, 158; 90; 69 and 78 for Co, Cr, Cu, Ni and Pb respectively and the limits of detection were 0.2, 0.2, 0.1, 0.5 and 0.1 mg kg(-1) respectively. The method was validated according to IUPAC recommendations. The combination of these techniques (DLLME-EDXRF) improves significantly the signal-to-noise ratio by concentrating the X-ray beam in a small diameter by applying a thin sample holder and removing the matrix effect. The developed methodology makes it possible to extend the application of EDXRF to quantify trace concentration of metal in soils.