SIMULTANEOUS DETERMINATION OF COBALT AND NICKEL BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH DIETHYLDITHIOCARBAMIC ACID

The reagent diethyldithiocarbamic acid has been examined for the high- performance liquid chromatographic separation of cobalt(II) and nickel (II) chelates on reversed-phase HPLC columns (150 x 3.9 mm) packed wit h Nova-Pak C-18, 4 mu m. The metal-diethyldithiocarbamic chelates were preconcentrated by solvent extraction. An aliquot of sample containin g copper, cobalt and nickel in a mixture was transferred to a well-sto ppered test tube to which was added reagent [diethyldithiocarbamic aci d 0.5% in ethanol-water (1:1), pH 10] and 10 ml organic solvent (dieth yl ether). After shaking with mechanical shaker for 5 min, the organic layer was separated and 0.1 ml transferred to another tube containing methanol (1 ml). The methanolic solution (15 mu l) was injected, on t he reversed-phase HPLC column. The complexes are eluted with methanol- water (75:25) at a flow-rate of 0.5 ml min(-1). The detection is carri ed out with a UV detector at 260 nm. The method shows several advantag es: short analysis time, minimized sample preparation, minimized effec t of interfering ions, a low detection limit (50 ppb for nickel and 5 ppb for cobalt) and good reproducibility, making it suitable for many types of samples, including alloys.