SPECTROPHOTOMETRIC DETERMINATION OF COBALT(II) IN WATER AFTER PRECONCENTRATION BY SORPTION OF ITS NITROSO-R COMPLEX WITH POLY(CHLOROTRIFLUOROETHYLENE) RESIN

A simple and rapid method has been established for spectrophotometric determination of cobalt(II) in water after preconcentration by sorbing the nitroso R (sodium-1-nitroso-2-hydroxynaphthalene-3,6-disulfonate) complex of cobalt(II) on poly(chlorotrifluoroethylene) resin. The cobalt-nitroso R complex was quantitatively retained on the resin as an ion associate complex with tetrabutylammonium cation in the range of pH 5.5 to 8.5. The retention capacity was 41.6 mug (0.71 mumol) Co g-1 resin at a maximum flow rate of 30 ml min-1. Cobalt retained on the resin column was completely extracted with 5 ml of methanol which was submitted to spectrophotometric measurement at 550 nm after 1 ml of 1.0 mol dm-3 nitric acid was added. The proposed method was applied to a river water sample.