A New Simple and Fast Method for Determination of Cobalt in Vitamin B12 and Water Samples Using Dispersive Liquid-Liquid Microextraction and Digital Image Analysis

In this work, a simple and fast method for the determination of cobalt in vitamin B12 and water samples was developed. The procedure is based on the preconcentration of the element using dispersive liquid-liquid microextraction (DLLME) and subsequent detection by digital image colorimetry. DLLME was performed with trichloroethylene (extraction solvent) and ethanol (dispersive solvent). The element was extracted in the form of its complex with 2-(2-thiazolylazo)-p-cresol (TAC). The optimal working conditions were obtained through univariate optimization. The variables studied were pH, the volume of extraction solvent, and the volume of dispersive solvent. Under optimal conditions, the method presented a limit of detection of 0.9 μg L −1 and precision (relative standard deviation) of 4.0%, for 25.0 μg L −1 cobalt solutions. The procedure was applied to the determination of cobalt in vitamin B12 and water samples. The method presents a simple, fast, and low-cost procedure, presenting itself as an excellent alternative to the determination of cobalt in the samples analyzed.