OPTIMIZATION OF WAVE-FORMS FOR PULSED AMPEROMETRIC DETECTION (PAD) OF CARBOHYDRATES FOLLOWING SEPARATION BY LIQUID-CHROMATOGRAPHY

Pulsed amperometric detection (p.a.d.) has recently gained prominence as a sensitive detection system for polar aliphatic organic compounds separated by liquid chromatography (l.c.). P.a.d. is based on the application of triple-step potential waveforms to incorporate amperometric detection with alternated anodic and cathodic polarizations to clean and reactivate electrode surfaces. These polarization steps result in the maintenance of uniform electrode activity for detection of organic compounds that typically are observed to "foul" noble metal electrodes during extended periods of amperometric detection at constant (dc) applied potential. Carbohydrates are easily separated with anion-exchange chromatography using alkaline mobile phases, and these alkaline conditions are appropriate for the direct detection of all carbohydrates at Au electrodes by p.a.d. The voltammetric and chronoamperometric responses are described here for selected carbohydrates, and guidelines are given for selection of optimal potential and time parameters in the waveform to be used for l.c.-p.a.d..