Direct spectrophotometric determination of cobalt(II) with nicotinohydroxamic acid in aqueous medium

Department of Chemistry, Sri. Meenakshi Government College for Women (Autonomous), Madurai-625 002, Tamilnadu, India

E-mail : muthuselviumashankar@gmail.com

Manuscript received online 10 July 2012, revised 12 August 2012, accepted 13 August 2012

A facile, sensitive and selective spectrophotometric method has been developed for the determination of cobalt(II) in pure form, water, effluent and alloy sample using a newly synthesized reagent, nicotinohydroxamic acid (NHA). Cobalt(II) forms a pink coloured complex with NHA in borate buffer medium (pH 9.2). Under optimum conditiuns, the maximum absorption of the complex was measured at 610 nm. The Beer's law obeys in the range of 0.65 to 5.9 µg mL^-1 of cobalt(Il). The molar absorptivity and the Sandell's sensitivity of the complex are 7.038 x 10⁴ L moJ^-1 cm^-1 and 0.0065 µg cm^-2/0.001 A, respectively. A detailed study of various interfering ions made the method more sensitive.