Speciation Studies of Cobalt (II) and Cobalt (III) and Its Application to Sample Analysis

Speciation studies of cobalt species, cobalt (II) and cobalt (III) have been carried out using spectrophotometric determination with the chromophoric reagent bis (5-bromosalicylaldehyde) orthophenilinediamine (BBSOPD). The methodology is direct and non extractive and is carried out in 40% ethanolic medium containing acetate buffer. The colour development is almost instantaneous and remained constant for over 24 h. The maximum absorbance was obtained at 458 nm. The average molar absorption coefficient was found to be 5.3 × 10 4 L mol 1 cm -1 . The calibration studies showed a correlation coefficient value of 0.995. The linear dynamic range is 0.26 mg L -1 . The interference due to cations, anions and complexing agents in the determination was evaluated. The method was applied to the determination of cobalt(II) and cobalt (III) in a synthetic mixture, tap water and sea water samples.