On-line electrochemical detection of carbohydrates coupled with the periodate oxidation

Abstract

A new concept of an amplified electrochemical detection of carbohydrates is proposed, where carbohydrates are oxidized by periodate ion (IO 4 −) in acidic solutions to yield iodate ion (IO 3 −) which would be electrochemically reduced into iodide ion (I −) under suitable conditions. This scenario allows highly sensitive detection of carbohydrates, for example, as 30 electrons per aldohexose molecule. Our cyclic voltammetric study revealed that IO 3 − is reduced at much lower overpotentials than IO 4 − at gold, platinum and carbon-based electrodes despite the fact that the standard redox potential of the IO 3 −/I − couple is more negative than that of the IO 4 −/I − couple. In the electrochemical reduction of IO 3 −, I − is considered to function as a mediator. Stable flow-through detection of IO 3 − in the presence of IO 4 − was realized at glassy carbon electrodes. This method was coupled with the IO 4 − oxidation of carbohydrates and the experimental conditions were partially optimized on a flow injection system. The IO 4 − oxidation-coupled electrochemical detection of carbohydrates was applied to ligand-exchange high-performance liquid chromatography in a post-column mode. Sub-nanomole order of carbohydrates were successfully detected on this system.