The aim of the present work was the development of a novel amperometric biosensor for rapid detection of sucrose in fruit juices samples. Two enzymes, invertase and fructose dehydrogenase (FDH), were immobilized onto a single-walled carbon nanotube paste (SWCNTP) electrode by wiring with a highly original osmium-polymer hydrogel. A second biosensor, for fructose only, was constructed containing inactive invertase and used for signal subtraction.

The biosensor exhibits a detection limit for sucrose of 2 mM, linearity up to 5 mM, good sensitivity of 1.98 mA cm^-2 mM, good reproducibility (RSD = 2.5%), fast response time (8s) and a stability of 4 months if kept under wet conditions at 4 °C.

The biosensor was successively tested for specific detection of sucrose and fructose in several commercial fruit juice samples and the results were compared with those obtained with a commercial spectrophotometric enzymatic kit.