Determination of polyhydroxy antibiotics by capillary zone electrophoresis with amperometric detection at a nickel electrode

Capillary zone electrophoresis (CZE) with amperometric detection at a nickel electrode for the determination of polyhydroxy antibiotics in alkaline solution is described. The electrode used was a 300 mu m diameter Ni disk electrode operated in a wall-jet configuration. With a working potential of +0.54 V and an 80 cm capillary (o.d. 360 mu m, i.d. 25 mu m) at 15 kV in the electrophoretic medium of 0.10 mol/l NaOH, a sample mixture containing seven different polyhydroxy antibiotics was separated within 20 min. The linearity varied over three orders of magnitude of concentration, the detection limit was 0.50 mu mol/l, for doublemycin, and the relative standard deviation of the peak current was about 5.5% in a period of 8 h. The method has been successfully employed to the determination of the purity of kanamycin, and the content of amikacin in human urines.