air-assisted liquid liquid microextraction combined with graphite furnace atomic absorption spectrometry for preconcentration and determination of trace amount of co(ii) and ni(ii) ions in water samples

A simple, rapid and efficient method has been developed for the extraction, preconcentration and determination of cobalt (II) and nickel (II) ions in water samples by air-assisted liquid-liquid microextraction (AALLME) coupled with graphite furnace atomic absorption spectrometry (GFAAS). In the proposed method, much less volume of an organic solvent was used as the extraction solvent in the absence of disperser solvent. Fine organic droplets were formed by sucking and injecting of the mixture of aqueous sample solution and extraction solvent with a syringe for several times in a conical test tube. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by GFAAS. Several variables that could affect the extraction efficiency were investigated and optimized. Calibration graphs were linear in the range of 6.5-100 ng L-1. Detection limits for Co and Ni were 2.3 ng L-1 and 3 ng L-1, respectively. The accuracy of the developed procedure was checked by analyzing NRCC-SLRS4 Riverine water as a certified reference material. Finally, the proposed method has been successfully applied for the determination of cobalt (II) and nickel (II) ions in tap, surface and river water samples.