Determination of trace levels of cobalt ion in different real samples using dispersive liquid–liquid microextraction followed by flame atomic absorption spectrometry

Dispersive liquid–liquid microextraction technique followed by flame atomic absorption spectrometry was used for preconcentration and determination of trace levels of Co(ІІ) in different real samples. Cobalt ion was first complexed by diethyldithiocarbamate (DDTC) followed by the extraction of resulting complex into the extraction solvent by dispersive liquid–liquid microextraction (DLLME). In DLLME, a mixture of 1.5 mL of methanol (as disperser solvent) containing 50 µL of carbon tetrachloride (as extraction solvent) was rapidly injected into the sample solution to extract the hydrophobic complex of Co-DDTC complex. Under the optimum conditions, the calibration curve was linear in the range of 40–300 µg L−1 of Co(ІІ) with a correlation coefficient of 0.9966. The relative standard deviation based on six replicate analysis of 100 µg L−1 of Co(ІІ) was 3.6% and the detection limit was 6.6 µg L−1. The accuracy of the proposed method was evaluated by the analysis of a certified reference material. Also, the proposed method was successfully applied for determination of trace levels of Co(ІІ) in different water, spinach leaves, black and green tea and tomato sauce samples.