Vortex Assisted Dispersive Liquid-Liquid Microextraction: Determination of Cobalt by HPLC

A simple an effective method was developed for preconcentration of cobalt in water samples. In the proposed approach, sodium diethyl dithiocarbamate (DDTC) was used as chelating agent, and vortex-assisted dispersive liquid-liquid microextraction combined with high performance liquid chromatography (HPLC) with UV detection was developed. In this method a small amount of chloroform as extracting solvent is rapidly injected by syringe into the water sample containing cobalt ions complexed by DDTC. This complex is extracted into the fine chloroform droplets and vortex agitation takes place during five minutes. The influence of variables affecting to the microextraction process were studied. Under the selected conditions, the preconcentration factor of 148 was achieved and the relative standard deviations (RSD) were 1.86% and 2.68% for 50 and 20 µg L-1 of cobalt, respectively. The proposed method was applied to analysis of water standard reference materials and the recovery range from 90.0 to 110.0%.