Evaluation of polypyrrole/glucose oxidase electrodes in flow-injection systems for sucrose determination

Abstract

Determination of sucrose in the presence of glucose is possible in a flow-injection system containing enzyme columns with glucose dehydrogenase, invertase, and mutarotase, immobilized on controlled porous glass using the fluorimetric measurement of enzymatically produced NADH. On the other hand, immobilization of enzymes to electrode surfaces in a defined way is of crucial importance for the development of fast and reliable amperometric enzyme electrodes. Preparation and functionalization of polypyrrole layers on platinum or glassy-carbon electrodes led to suitable surfaces to which glucose oxidase was covalently bound via amides or secondary amines. The electrodes show fast response times and good long-term stability in flow-injection systems and stationary amperometric measurements for the determination of glucose. By combination of two polypyrrole/glucose oxidase electrodes with immobilized invertase and mutarotase in automatic flow-injection systems fast sucrose determination should be possible. However, as sucrose proved to be an inhibitor for glucose oxidase, the response of the electrodes was suppressed, especially when the enzyme was immobilized in a very thin film on the electrode surface. Thus, the flow-injection systems and the polypyrrole/glucose electrodes must be modified or adapted to be used for the determination of glucose in the presence of sucrose.