Helmut Moderegger

(Bio)sensors based on manganese dioxide-modified carbon substrates: retrospections, further improvements and applications

An overview is presented which summarizes our accomplishment in the development of sensors and biosensors based on heterogenous carbon electrodes modified with manganese dioxide. Brief account of each sensor and biosensor has been given and example of real sample applications provided where appropriate.

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 MnO(2) 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-d-glucopyranoside, as well as in beer samples by flow-injection analysis (FIA). The biosensor could be operated under physiological conditions (0.1M 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 0.2mLmin(-1), injection volume 0.25mL, operation potential 0.48V versus Ag/AgCl) extends from 11 to 13,900mumolL(-1) glucose in free form. The limit of detection (3sigma) is 1mumolL(-1) glucose. A concentration of 100mumolL(-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 2h with glucosidase). Bonded glucose could be determined in beer samples using the same assay. The results corresponded very well with the reference procedure.

AMPEROMETRIC DETERMINATION OF GLUCOSE WITH AN MnO2 AND GLUCOSE OXIDASE BULK-MODIFIED SCREEN-PRINTED CARBON INK BIOSENSOR

A simple biosensor, constructed by bulk-modification of carbon ink with manganese dioxide as a mediator and glucose oxidase as a biocomponent was investigated for its ability to serve as amperometric detector for glucose in hydrodynamic as well as in flow injection analysis (FIA) mode. The sensor could be operated at a potential of 0.48 V under physiological conditions (0.1 M phosphate buffer, pH 7.5) and exhibited excellent reproducibility and stability. Factors influencing the amperometric response such as injection volume, flow rate and applied working potential were studied in detail. The screen-printed electrode exhibited a linear amperometric increase with the concentration of D-glucose from 2 to 2500 mg L−1 and gave a 3σ detection limit of 0.085 mg L−1. Due to its remarkable stability such a sensor could be operated continuously for more than four weeks or more than 1000 sample injections. No change of signal height could be observed within an operation period of 12 h. The sensor was exploited for FIA-amperometric determination of glucose in beer and wine samples