A novel separation/preconcentration technique based on ultrasonic dispersion liquid-liquid microextraction for determination of trace cobalt by flame atomic absorption spectrometry

Abstract

An improved method for the determination of trace cobalt in water samples has been developed using ultrasonic dispersion liquid-liquid microextraction (US-DLLME) prior to flame atomic absorption spectrometry (FAAS) analysis. In this method, cobalt was extracted into the fine droplets of carbon tetrachloride after chelate formation with the water soluble ligand, ammonium pyrrolidine dithiocarbamate (APDC). The fine droplets of carbon tetrachloride were formed and dispersed in the aqueous sample with the help of ultrasonic waves which accelerated the formation of the fine cloudy solution without using disperser solvents. Under optimum conditions, the calibration curve was linear in the range of 2.5-500 μg L -1 , with a detection limit of 0.8 μg L -1 . The relative standard deviation (RSD) for ten replicate measurements of 20 and 500 μg L -1 of cobalt were 3.3 and 2.2%. This proposed method was successfully applied to tap water, river water, and sea water, and accuracy was assessed through the analysis of certified reference water or recovery experiments. Operation simplicity, low cost, high enrichment factor, and low consumption of the extraction solvent are the main advantages of the proposed method. KEY WORDS : Ultrasonic dispersion liquid-liquid microextraction, Preconcentration, Atomic absorption spectrometry, Cobalt Bull. Chem. Soc. Ethiop. 2012 , 26(1), 9-18. DOI: http://dx.doi.org/10.4314/bcse.v26i1.2