A novel micellar medium using triblock copolymer for cobalt determination.

This work proposes a new method for Co(II) determination based on the use of the triblock copolymer as micellar medium instead of chloroform. The proposed strategy is environmental friendly because the copolymer is biodegradable and nontoxic. The method is based on the formation of a cobalt-1-nitroso-2-naphthol complex, in the micellar triblock copolymer compound solution constituted by polyethylene oxide (PEO) and polypropylene oxide (PPO). Experimental conditions such as pH, the molecular weight and the PEO/PPO ratio of triblock copolymer were optimized. Results obtained for cobalt determination in vitamins with this novel method showed excellent agreement with those obtained using atomic absorption spectrometry. The relative standard deviation for a solution containing 0.125 mg L(-1) Co was 1.0% (n = 5); the relative error varied from 2.8 to 4.4%; the detection limit was 13.3 microg L(-1) and the quantification limit was 44.3 microg L(-1).