Abstract
A cloud point extraction (CPE) procedure was developed for the separation and preconcentration of trace amounts of cobalt prior to its determination by flame atomic absorption spectrometry (FAAS). The procedure is based on the formation of Co(II) complex with 2-[(2-mercaptophenylimino)methyl]phenol (MPMP) followed by its extraction into a Triton X-114 surfactant-rich phase. Some important parameters affecting both complexation and extraction, such as pH, concentrations of chelating agent and surfactant, temperature, and time of equilibration, were optimized. Under optimum conditions, the preconcentration of a volume of 25 mL of sample resulted in a limit of detection of 0.21 µg L-1, an enhancement factor of 97, and a relative standard deviation of 1.2 % (n = 8, 60 µg L-1) for the determination of Co(II) by FI-FAAS. This procedure was successfully applied to water, vitamin B12 and B-complex samples. The accuracy was assessed employing addition-recovery experiments, independent analysis by graphite furnace atomic absorption spectrometry and by using a certified reference material.
Highlights
Cobalt is an essential trace element present in most body tissues, with the highest concentrations typically found in the liver
The effect of the Triton X-114 concentration on cobalt extraction was evaluated by varying the surfactant concentration in the range of 0.04-0.2% (v/v)
The results showed that the maximum signal intensity for Co (II) was obtained at temperatures between of 45 and 60 °C
Summary
Cobalt is an essential trace element present in most body tissues, with the highest concentrations typically found in the liver. It is a component of vitamin B12 (cyanocobalamin), which is involved in the production of the blood red cells and the prevention of pernicious anemia.[1,2] Cobalt toxicity is quite low compared to many other metals. Despite the development of new, more sensitive analytical methods, the determination of cobalt in natural samples still remains a challenge. The analytical instrumentation available does not present the sensitivity requirements necessary to analyze this type of sample.
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