Optical sensing films using organically modified silicates (ormosils) as a matrix for the determination of ammonia in water based on immobilized a fluorescent indicator aminofluorescein (AF) have been investigated. The sensing film was stability for 6 months. The detection limit of ammonia for different kind of ormosils precursors ranges from 0 01 to 0 5 μg·ml -1 (S/N 2). The response time was less than 10 min.SupportedbyNaturalScienceFoundationofFujian ;;China (D1 1 1 0 1 1
