Direct and derivative spectrophotometric determination of cobalt(II)with 2,4-dihydroxybenzaIdehyde isonicotinoyl hydrazone

摘要

A simple and sensitive spectrophotometric method is developed for the determination of cobalt in aqueous medium.The metal ion forms a brown coloured partially soluble complex with 2,4-dihydroxybehzaldehyde isonicotinoyl hydrazone(2,4-DHBINH)in the pH range 2-10.However,the complex is found to be soluble in 25% aqueous DMF.The complex shows an absorbance maximum at 405 nm in the pH range 5-6.Beer's law is obeyed in the range 0.062-1.5 mu g/ml at pH 5.5.The molar absorptivity and the Sandell's sensitivity of the method are 3.20+-0.03X10~4 L mol~(-1)cm~(-1)and 0.0074 mu g/cm2 respectively.The composition of the complex is 1:1.A method for the determination of cobalt by first order derivative spectrophotometry is also proposed.The method is applied for the determination of cobalt in alloy steel samples.