A Simple Spectrophotometric Method for the Determination of Cobalt (II) using 1-Nitroso-2-Naphthol in Anionic Aqueous Solution of Sodium Dodecyl Sulphate

Author(s): Gul Afshan Soomro and Ghulam Abbas Shar

A simple rapid new spectrophotometric method has been developed for the determination of cobalt at trace level using 1-nitroso-2-naphthol (NNPh) in presence of anionic aqueous micellar solution surfactant 1.0% sodium dodecyl sulphate (SDS). NNPh reacts with cobalt (II) to form green coloured tris (1-nitroso-2-naphtholato) cobalt complex. The importance of this method is the use of micellar system which replaces the previous solvent extraction steps while enhancing the sensitivity, selectivity and the molar absorptivity which reduces the cost and toxicity. The average molar absorption coefficient and Sandell's sensitivity was found to be 2.05 × 104 L mol-1cm-1 and 3.49 ng cm-2at λmax 436.2 nm. Linear calibration graph was obtained over the concentration range 0.12-4.0 μgmL-1, the stoichiometric composition of the chelate was 1:3 (Co: [NNPh]3. The developed method was successfully applied for the determination of cobalt from alloy and pharmaceutical samples.

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