Picoline based-homogeneous liquid–liquid microextraction of cobalt(ii) and nickel(ii) at trace levels from a high volume of an aqueous sample

Abstract

A new homogeneous liquid–liquid microextraction method using 3-picoline has been developed for preconcentration and extraction of cobalt(II) and nickel(II) ions from a high volume of an aqueous sample. In the proposed method, 3-picoline is simultaneously used as a complexing agent and an extraction solvent. Initially to 25 mL of the aqueous sample containing the analytes, 3-picoline is added to complex the studied cations. Then sodium chloride is added to this homogeneous solution. After manual shaking, the tube is placed in a water bath. Due to the decrease of 3-picoline solubility in water at high temperatures, a cloudy solution is formed. The fine droplets of 3-picoline containing cation–picoline complexes are collected on the top of the aqueous phase by centrifuging. The enriched analytes in the upper phase are determined by graphite furnace atomic absorption spectrometry. Several variables possibly affecting the extraction efficiency were investigated and optimized. Under the optimum conditions the calibration curves were linear in the ranges of 10–150 and 5–125 ng L⁻¹ for cobalt(II) and nickel(II), respectively. The detection limits were obtained to be 3.8 and 2.2 ng L⁻¹ for cobalt(II) and nickel(II), respectively. Finally, the proposed method has been successfully applied for simultaneous analysis of the analytes in different environmental aqueous samples.