An optical-fibre sensor for fluoride

The optical sensor is based on the formation of a fluoride ternary complex from an immobilized fluorescent binary zirconium-calcein blue chelate at pH 2.2. The enhanced fluorescence enables fluoride to be determined in the range 2.63 × 10^?5 ?4.21 × 10^?4 M (0.5–8.00 mg l^?1) with a limit of detection of 2.63 × 10^?5 M. The response of the sensor to fluoride is affected by ionic strength and temperature. The response time depends on the particle size and the packing density of the polymer (XAD-4) substrate used.