Fluorimetric determination of fluoride in a flow assembly integrated on-line to an open/closed FIA system to remove interference by solid phase extraction

A simple flow injection fluorimetric method for fluoride determination is proposed. The method is based on the enhanced fluorescence of quercitin–Zr(IV) complex when fluoride ion is present in the sample. An open/closed FIA manifold with a mini-column of Dowex 50W X8 resin was used to remove the most important interference (aluminum). The two FIA assemblies were integrated on-line to automate the pretreatment of the water sample and fluoride determination. The calibration graph was linear over the range 0.1–3.0 μg ml −1 of fluoride with a correlation coefficient of 0.999 and LOD 0.06 μg ml −1. The relative standard deviation was 2.5% and the sample throughput was 52 h −1 without pretreatment and 10 h −1 with pretreatment of the sample. The method was applied to the determination of fluoride in water samples.