EXTRACTIVE SPECTROPHOTOMETRIC DETERMINATION OF COBALT

A new, simple, and selective extraction-spectrophotometric method for the determination of cobalt in the soil extract is described. The meth od is based on the extraction of Co(II)-SCN- complex with toluene solu tion of N-octylacetamide (OAA) in the presence of cationic surfactant i.e. cetylpyridinium chloride (CPC), and the subsequent heating of the extract for at least 10 min at 60 +/- 5 degrees C in a water bath. Th e value of apparent molar absorptivity of the complex is 2.55 x 10(4) l mol(-1) cm(-1) at absorption maximum 625 nm. The detection limit of Co is 15 ppb. The composition of the complex, and optimization of the analytical variables have been established. The method is highly selec tive and none of the tested diverse ions interfered in the determinati on of Co. The method has been used for field detection of Co in the so il extracts.