Abstract: Separation of cobalt, nickel and copper elements as their 2-(6-methyl-2-benzothiazolyazo)-5-dimethylaminophenol complexes by capillary electrophoresis in nonaqueous medium was first presented. Ethanol and N,N-dimethylformamide(DMF) were evaluated for the effect of nonaqueous solvents on electroosmotic flow. The influence of the pre column derivitization conditions, some parameters such as choice and selection of organic solvents, concentration ratio in mixed nonaqueous medium, applied voltage on the separation were also investigated. Under the optimum conditions(buffer: 40 mmol/L, pH5.0 NaAc-HAc in ethanol(50%) and DMF(50%) mixture, 30 kV, 575 nm as detection wavelength), the three ions were separated in₆min successfully, and detection limits of 9.18×10^-8mol/L, 2.79×10^-7mol/L and 4.47×10^-7mol/Lfor cobalt, nickel and copper were achieved, respectively. The theoretical plate number reached up to 3.2×10⁵/m.

Key words: Pre-column derivitization, Nonaqueous capillary electrophoresis, Metal ions