Amperometric determination of bonded glucose with an MnO2 and glucose oxidase bulk-modified screen-printed electrode using flow-injection analysis

A screen-printed amperometric biosensor based on carbon ink double bulk-modified with MnO2 as a mediator and glucose oxidase as a biocomponent was investigated for its ability to serve as a detector for bonded glucose in different compounds, such as cellobiose, saccharose, (-)-4-nitrophenyl-beta-glucopyranoside, as well as in beer samples by flow-injection analysis (FIA). The biosensor could be operated under physiological conditions (0.1 M phosphate buffer, pH 7.5) and exhibited good reproducibility and stability. Bonded glucose was released with glucosidase in Solution. and the free glucose was detected with the modified screen-printed electrode (SPE). The release of glucose by the aid of glucosidase from cellobiose. saccharose and (-)-4-nitrophenyl-beta-D-glucopyranoside in solution showed that stoichiometric quantities of free glucose could be monitored in all three cases. The linear range of the amperometric response of the biosensor in the FIA-mode flow rate 0.2 mL min(-1), injection volume 0.25 mL, operation potential 0.48 V versus Ag/AgCl extends from 11 to 13,900 mu-mol L-1 glucose in free form. The limit of detection (3sigma) is 1 mumol L-1 glucose. A concentration of 100 mumol L-1 yields a relative standard deviation of approximately 7% with five injections. These values correspond to the same concentrations of bonded glucose Supposed that it is liberated quantitatively (incubation for 2 h with glucosidase). Bonded glucose could be determined in beer samples using the same assay. The results corresponded very well with the reference procedure. (C) 2004 Elsevier B.V. All rights reserved.