Fast wave forms for pulsed electrochemical detection of glucose by incorporation of reductive desorption of oxidation products.

The electrochemical activity of Au electrodes held at constant potential for anodic detection of carbohydrates in alkaline media eventually decays to zero. This loss of response is a consequence of the accumulation of adsorbed oxidation products on the electrode surface. Although it is well-known that these "poisons" can be removed by oxidative desorption simultaneously with formation of surface oxide, we have discovered that electrodes fouled during the detection of glucose yield a cathodic peak at -0.77 V vs SCE resulting from reductive desorption of these species. Incorporation of the reductive desorption process into wave forms for pulsed electrochemical detection (PED) permits a significant decrease in the time periods traditionally allowed for the oxidative and reductive reactivation of the electrode with a resulting increase in wave form frequency. A 6.7-Hz wave form using E(red) = -1.00 V (t(red) = 10 ms), E(oxd) = +0.60 V (t(oxd) = 10 ms), and E(det) = +0.10 V (t(del) = 50 ms, t(int) = 50 ms) is applied for detection of glucose in a LC-PED system and is demonstrated to yield a sub-picomole detection limit with a linear dynamic range extending over three decades.