Dispersive liquid–liquid microextraction based on solidification of floating organic drop combined with flame atomic absorption spectrometry for determination trace amount of cobalt in water samples

An efficient, rapid, simple, and highly selective dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFOD), combined with flame atomic absorption spectrometry was developed for preconcentration and determination of trace amounts of cobalt in water samples. In this method, an appropriate mixture of acetone and 1-undecanol was injected rapidly into the aqueous sample containing cobalt-2N1N complex, as a result cloudy mixture was formed. After centrifugation, the test tube was cooled for 5 min. The solidified 1-undecanol on top of the solution was transferred into a suitable vial. Then, it was dissolved in 100 μL of methanol and finally introduced into the flame atomic absorption by microsampler injector. Several factors influencing the microextraction efficiency, such as the nature and volume of organic solvent, pH of aqueous solution, amount of complexing agent, stirring rate and extraction time were investigated and optimized. Under the optimum conditions, the enhancement factor was 68. The limit of detection, 6 μgL and relative standard deviation (RSD) 2.64% (n=8) were obtained. The proposed method was applied to the analysis of various water samples.