Numerous carbohydrates can be oxidized at low positive po-tentials at chemically modified carbon paste electrodes con-taining added cobalt phthalocyanine (CoPC). Although no response Is observed at plain carbon paste electrodes, a diverse group of carbohydrates Including mono- and di-saccharides, pyranose and furanose rings, and reducing and nonreducing sugars are readily oxidized at the modified electrode surface. In 0.15 M NaOH, the oxidations exhibit a cyclic voltammetrlc peak potential of+ 0.40 V vs. Ag/AgCI, the waves decreasing In magnitude and shifting to more positive potentials at less basic pH. The CoPC electrodes can be used forelectrochemical detection of the carbohydrates In liquid chromatography as long as the applied potential Is regularly pulsed to-0.3 V or lower. Detection limits obtained In this manner range from 100 pmol Injected for glucose and maltose to 500 pmol Injected for fructose and sucrose.

In recent years, several electrochemical approaches have been proposed for use in the flow injection or high-perform-ance liquid chromatographic (HPLC) analysis of carbohydrates (1-15). These approaches are of particular interest because carbohydrates do not exhibit significant absorption at wavelengths above 210 nm and thus are not well suitedfor the absorption and fluorescence detection methods most commonly employed in HPLC. As a consequence, monitoring of sugars has ordinarily been performed either by refractive index detection of the intact carbohydrates or by chemical derivatization with strongly absorbing or fluorescing groups. Many carbohydrates—most notably, the reducing sugars—are known for the ease with which their chemical