NEW FRUCTOSE BIOSENSORS UTILIZING A POLYPYRROLE FILM AND D-FRUCTOSE 5-DEHYDROGENASE IMMOBILIZED BY DIFFERENT PROCESSES

Two amperometric biosensors for fructose detection were developed by i mmobilizing D-fructose 5-dehydrogenase by two different immobilization processes. For the first biosensor, the occlusion enzymatic immobiliz ation technique was employed, the enzyme being immobilized in a polypy rrole (PPY) film, over a platinum electrode containing sodium ferricya nide as mediator. With this sensor, about 100 analyses were performed over a period of 1 week with daily use. The second was constructed usi ng the crosslinked covalent bond method, the enzyme being immobilized onto a PPY film doped with hexacyanoferrate supported on a platinum el ectrode surface. This biosensor was used for, approximately, 200 analy ses in 2 weeks of continuous use. Analytical parameters, such as pH, i onic strength, interferences and response time of both sensors were al so studied. The biosensors were utilized for fructose determinations i n three different samples of dietetic products and presented a good co rrelation with the standard colorimetric method. A linear response ran ge to both biosensors was 0.1-0.8 mmol l(-1) fructose with a r.s.d. of 0.68%. (C) 1998 Elsevier Science B.V. All rights reserved.