Spectrophotometric determination of cobalt(II) and gold(III) in the presence of potassium persulphate using resacetophenone oxime

Cobalt(II) and gold(III) react with 2,4-dihydroxy acetophenone oxime (RPO) forming yellowish brown and greyish green coloured soluble complexes respec tively. The reactions are very slow but become fast in the presence of K2S2 O8. This may be due to the enhancement of aerial oxidation of metal complex es with RPO in their lower oxidation states (Co(II), Au(III)) to coloured c omplexes with higher oxidation state (Co(III), Au(V)). The Co(III)-RPO comp lex shows lambda (max) at 390 nm and at pH 9.5 obeying Beer's law in the ra nge 0.12 - 1.80 mug/ml. Determination of Au(III) is carried out at 630 nm a nd pH 3.5 where Beer's law is obeyed in the range of 0.39-5.12 mug/ml of Au (III). The effect of foreign ions in the method is studied. The method is a pplied for the analysis of Co(II) in vitamin B-12 and Au(III) in Rheumartho Pharmaceutical sample.