H-point standard addition method for simultaneous spectrophotometric determination of Co(II) and Ni(II) by 1-(2-pyridylazo)2-naphthol in micellar media

Abstract

A very simple and selective spectrophotometric method for simultaneous determination of Co(II) and Ni(II) by 1-(2-pyridylazo) 2-naphthol (PAN), in micellar media, using H-point standard addition method (HPSAM) is described. The ligand and its metal complexes (Co(II)–PAN and Ni(II)–PAN) were made water-soluble by the neutral surfactant Triton X-100, and therefore, no extraction with organic solvents was required. Formation of both the complexes was complete within 10 min at pH 9 (adjusted by ammonia buffer). The linear range was 0.10–2.00 μg ml −1 for Co(II) and 0.05–1.50 μg ml −1 for Ni(II). The relative standard deviation (R.S.D.) for the simultaneous determination of 0.50 μg ml −1 each of Co(II) and Ni(II) was 2.32 and 3.13%, respectively. Interference effects of common anions and cations were studied and the method was applied to simultaneous determination of Co(II) and Ni(II) in alloy samples. The method was compared with derivative spectrophotometric method.