Silver electrodes, when conditioned at sufficiently positive potentials in the presence of a strong base, can be made to form a silver(1) oxide or silver(I1) oxide surface. In the presence of this oxide surface, carbohydrates may be oxidized and quantitated by means of an electrocatalytic scheme. The current which flows to reoxidize the charge-transfer mediator (silver oxide) is directly related to concentration of carbohydrate. Rectilinear response is obtained over at least IXO decades of concentration M to discussed. The application of a high-performance liquid chromatography (HPLC) detector for the separation of some common sugars is illustrated.M). Design of a prototype electrochemical cell and studies of optimum cell conditions are

When a silver electrode is conditioned in a solution of 0.5 M sodium hydroxide with added sodium phosphate and using a dual pulse (500 mV/750 mV vs. Ag/AgCl), a stable silver(I)/silver(II) oxide surface is formed. It has been previously shown that various moieties react with the silver(II) oxide in a chemical oxidation at the outer surface of the oxide layer. This is then followed by re-oxidation of the silver with the generation of current at approximately 500 mV relative to the silver/silver chloride electrode. Previously we found the need to remove carbon dioxide from the base and condition the electrode in a solution containing phosphate ion in order to provide mechanical stability to the oxide layer. We have previously shown this electrode to be applicable to the detection of a variety of carbohydrates. The applicability of the silver oxide/silver phosphate electrode to the post-chromatographic amperometric detection of amino acids was investigated. Calibration studies of amino acids representative of the various classes demonstrated good sensitivity and linearity in the 1 -100 mM range. Responses of amino acids were measured using glucose as an external standard, in order to correct for variability of the oxide layer. Relative responses of the amino acids ranged from 3 down to 0.1. Correlation with structure suggested the importance of absorption in determining the rate of oxidation. Comparison of arginine with n-benzoyl-l-arginine ethyl ester indicated that side chains as well as the backbone amino group can be oxidized. A Levitch plot of alanine was shown to be linear from approximately 30 to 300 radians per second spin rate at a scan rate of 50 mV per second. Application to post-chromatographic detection was demonstrated.

The response of the silver oxide electrode to carbohydrates, polyhydroxy compounds and amines is dependent on several factors. These include the number of oxidizable groups on the substrate and the way in which the electrode surface is prepared, including the potential program, the thickness of the oxide layer, the surface area and the presence of other species in the solution during electrode conditioning. Studies of these factors led to a pulsed potential program for the conditioning and maintenance of electrode stability, with the incorporation of phosphate during the initial conditioning process. This method led to a response to 10 ¹4 M glucose, which was reproducible for at least forty repeated injections and stable for at least four hours with a relative standard deviation of 5.2 %. This response was also reproducible on successive days when the electrode was prepared in the same manner.

No abstract

The response of the silver oxide electrode to carbohydrates, polyhydroxy compounds and amines is dependent on several factors. These include the number of oxidizable groups on the substrate and the way in which the electrode surface is prepared, including the potential program, the thickness of the oxide layer, the surface area and the presence of other species in the solution during electrode conditioning. Studies of these factors led to a pulsed potential program for the conditioning and maintenance of electrode stability, with the incorporation of phosphate during the initial conditioning process. This method led to a response to 10−4M glucose, which was reproducible for at least forty repeated injections and stable for at least four hours with a relative standard deviation of 5.2 %. This response was also reproducible on successive days when the electrode was prepared in the same manner.