PULSED AMPEROMETRIC DETECTION OF CARBOHYDRATES SEPARATED BY CAPILLARY ELECTROPHORESIS

Working conditions for operation of a 10-mum Au electrode have been evaluated for the detection of eight carbohydrates separated by capillary electrophoresis. The voltage pulse sequence consisted of 300 mV (vs SCE) for 165 ms, 1200 mV for 55 ms, and -800 mV for 165 ms; carbohydrate oxidation was monitored in the first pulse. Sampling times of 55 ms were used during the 300-mV pulse, and maximum sensitivity was observed for the second 55-ms sampling period. Detection limits were in the low-femtomole range for separation in 10-mum capillaries with a 0.1 mol/L sodium hydroxide electrolyte. A linear working range was observed from 10(-6) to 10(-4) mol/L, and peak height reproducibility for inositol was 2%. Separation efficiencies were in the range of 100 000-200 000 theoretical plates, but some degradation of capillary performance was observed with time.