Composite alcohol biosensors based on solid binding matrix

A group of solid compounds with amphiphilic character called solid binding matrices (SBMs), which present a new concept of solid composite transducer for amperometric biosensors, were used for construction of robust solid alcohol biosensors. The enzymes, alcohol dehydrogenase (ADH) and diaphorase (DP) were either placed on the surface of the SBM-based transducer containing NAD(+) or they were incorporated together with NAD(+) directly into the transducer. The use of various mediators (organic dyes, vitamin K-3, hexacyanoferrate(III), ferrocene) and methods of biosensor construction were studied. The electrochemical properties and the characteristics of the composite ethanol biosensors are described. The electrode response was fast and reproducible As the response to ethanol in the range 0.2-4.0 mM was not linear, the calibration curves were transformed (1/Delta i = f(1/c)) to obtain the linear dependencies. The biosensors were used for the determination of ethanol in samples of wine, resulting in a good agreement with data determined by photometric measurements after distillation of the sample (average percentage accuracy was 2% for surface layer-modified and 2.5% for bulk-modified bioelectrodes). The surface-modified sensors remained stable for at least 3 months. The sensitivity of bulk-modified sensors decreased to 60-85% of the initial value after 1 month, but after electrode surface renewal about 90% of initial sensitivity was found. (C) 1998 Elsevier Science S.A. All rights reserved.