a fast responding glucose biosensor for the continuous determination of glucose is presented. the biosensor is based on an oxygen optrode, which measures the consumption of oxygen via dynamic quenching of the fluorescence of an indicator by molecular oxygen glucose oxidase (god) is immobilised onto the surface of this oxygen optrode by adsorption to carbon black and by crosslinking with glutardialdehyde. carbon black is used as an optical isolation to protect the optrode from the interference of ambient light and sample fluorescence. the measurements were performed in a flow through cell with air saturated glucose standard solution (phosphate buffered saline ph 6.9). the effect of four different qualities of god in relation to response times (the time required to reach 90 of the steady-state signal $tau$ //9//0, was 8-60 s, the linear analytical range (0.01 to 2 mm glucose) and the long-term stability ( $tau$ // $one half$ was 1-20 weeks) were investigated. a simple device is presented capable of enlarging the analytical range up to 200 mm glucose concentration. (author abstract) 11 refs