VARIATION IN PED RESPONSE AT A GOLD MICROELECTRODE AS A FUNCTION OF WAVE-FORM PARAMETERS WHEN APPLIED TO ALDITOLS AND CARBOHYDRATES SEPARATED BY CAPILLARY ELECTROPHORESIS

Results are presented from a systematic study of the noise (N) and pea k-to-noise ratio (P/N) obtained for pulsed electrochemical detection ( PED) at a gold micro-wire electrode applied to a mixture of alditols a nd monosaccharides separated by capillary electrophoresis (CE). The el ectrode potentials and time periods for oxidative cleaning and reducti ve reactivation of the electrode were held constant in the PED wavefor m at minimum allowable values and the time period for digital integrat ion of electrode current (t(int)) was varied from 50 to 800 ms by 50-m s intervals. The value of N was virtually independent of t(int) and P/ N increased approximately as a linear function of t(int) in the range 50-200 ms corresponding to waveform frequencies in the range 4.5-2.7 H z. A detection limit of 9 fmol glucose was determined for a 4-nL injec tion using t(int) = 200 ms.