STABILITY IMPROVEMENT OF OPTOCHEMICAL SOL-GEL FILM SENSORS BY IMMOBILIZATION OF DYE-LABELED DEXTRANS

To improve the stability of optochemical sensors the immobilisation of dextran labeled with fluorescent dyes in sol-gel films was investigat ed. The results of a pH-sensor based on dextran labeled with fluoresce in were compared to sensors made by physical entrapment of the dye in the sol-gel matrix. The use of fluorescein-dextran for sensor preparat ion increased stability drastically. To develop stable mercury-sensiti ve films porphyrin derivatives were covalently bound to dextran and im mobilized according to the procedure used for pH sensors. The stabilit y of the resulting mercury sensors was longer than 6 weeks.