COMPOSITE ALCOHOL BIOSENSORS BASED ON SOLID BINDING MATRIX

A group of solid compounds with amphiphilic character called solid bin ding matrices (SBMs), which present a new concept of solid composite t ransducer for amperometric biosensors, were used for construction of r obust solid alcohol biosensors. The enzymes, alcohol dehydrogenase (AD H) and diaphorase (DP) were either placed on the surface of the SBM-ba sed transducer containing NAD(+) or they were incorporated together wi th NAD(+) directly into the transducer. The use of various mediators ( organic dyes, vitamin K-3, hexacyanoferrate(III), ferrocene) and metho ds of biosensor construction were studied. The electrochemical propert ies and the characteristics of the composite ethanol biosensors are de scribed. The electrode response was fast and reproducible As the respo nse 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 dep endencies. The biosensors were used for the determination of ethanol i n 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 bul k-modified bioelectrodes). The surface-modified sensors remained stabl e for at least 3 months. The sensitivity of bulk-modified sensors decr eased to 60-85% of the initial value after 1 month, but after electrod e surface renewal about 90% of initial sensitivity was found. (C) 1998 Elsevier Science S.A. All rights reserved.