Enhancement of LCEC Response by Use of Rectrochemically Pretreated Glassy Carbon Electrodes

A simple electrochemical pretreatment procedure has been shown to increase the selectivity of LCEC detection by lowering the required operating potential compared to that needed at conventional untreated glassy carbon. The effect of a conditioning procedure consisting of sequential application of brief positive and negative potentials to a polished glassy carbon surface was examined for a group of model LCEC analytes including p-hydroquinone, dopamine, dihydronicotinamide adenine dinucleotide (NADH), ascorbic acid, and hydrazine. The lowering of the potential required for detection of these species was greatest for the irreversibly oxidized systems which exhibit the largest overvoltage at untreated glassy carbon–natnely, NADH, ascorbic acid, and hydrazine. For these species at pretreated electrodes, comparable detector response was achieved using potentials 0.2 to 0.5 V less than that otherwise needed for optimum response. The improved performance of the electrochemically pretreated electrodes was maintained over a wide range of pH conditions and mobile phase compositions and dramatically facilitated the determination of the latter set of compounds in physiological matrices.