Development of a green dispersive liquid-liquid microextraction method using a home-made tablet disperser for extraction and preconcentration of Co(II) and Ni(II) from high volume aqueous samples

An analytical approach for the determination of trace amounts of Co(II) and Ni(II) has been proposed using a home-made tablet-based dispersive liquid-liquid microextraction method performed in a narrow-bore tube followed by flame atomic absorption spectrometry. In this method, a mixture of tartaric acid, sodium bicarbonate, and NaCl are used to make the disperser tablet. Then µL-level of an extraction solvent is added on the tablet, and it is released into a narrow-bore tube containing sample solution and a complexing agent. An acid-base reaction between tartaric acid and sodium bicarbonate is immediately occurred, and the produced CO2 leads to dispersion of the extraction solvent as tiny droplets into the solution and subsequent extraction of the analytes. The proposed method made possible the determination of Co(II) and Ni(II) in the ranges of 0.1-15.0 and 0.3-18.0 µg L-1, respectively. Repeatability of the proposed method, expressed as relative standard deviation, was obtained 3.6% and 2.8% (n=6, C=1 µg L-1) for Co(II) and Ni(II), respectively. Relative recoveries (89-97%, obtained at two fortification levels) confirmed the usefulness of the method for analysis of the analytes in the environmental water samples. The method was shown to be fast, reliable, and environmentally friendly with low organic solvent consumption.