RESUMO
In this study, a method based on direct-immersion single-drop microextraction was developed for the determination of vanadium in water. The detection system uses digital images obtained directly from the solvent drop after the sorption of V(V). The extraction solvent used was the ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]). The images were obtained directly from the solvent drop, with the aid of a camera. The digital images were stored, and the RGB (red, green, and blue) data were obtained. The data collected by the red channel were used to construct the analytical curve since it showed higher sensitivity compared with green and blue channels. Under optimized conditions, the method presented an enrichment factor of 50 and a limit of detection of 0.6 µg L-1 for 3.5 mL sample volume. The limit of quantification and the relative standard deviation (50.0 µg L-1) obtained were 1.8 µg L-1 and 4.8%, respectively. Certified reference material (Plankton) was used to assess the accuracy of the method. The simple, fast, efficient, and low-cost procedure was successfully applied to the determination of V(V) in water samples. The proposed method is also following the principles of green chemistry since it uses minimal volumes of samples, reagents, and solvents and yields a small amount of waste.
RESUMO
In this work, a method using ultrasound-assisted emulsification microextraction (USAEME) without the use of ligands in an online system for preconcentration and determination of cadmium was developed. The method was based on the preconcentration of cadmium by USAEME, employing trichloroethylene as the extraction solvent, and subsequent retention of the rich phase in a mini-column packed with silica gel. The extracted metal was determined by flame atomic absorption spectrometry. The parameters that affect the extraction of cadmium were optimized using the univariate method. Under optimized conditions, the method presented a limit of detection of 0.17 µg/L, a limit of quantification of 0.57 µg/L, an enrichment factor of 56, and a consumptive index of 0.18 mL/min. The accuracy of the method was tested by analyzing the certified reference material, National Institute of Standards and Technology (NIST) 1573 (tomato leaves). The determination of Cd in water (drinking water, bottled water, river water, and seawater) and tea (black and green tea) samples was also performed using the proposed method. The method is simple, efficient, and eco-friendly because it requires low consumption of an organic solvent.
