Automatic microdistillation flow-injection system for the spectrophotometric determination of fluoride.

An automatic flow-injection (FI) system including on-line separation by microdistillation and spectrophotometric detection has been developed for the determination of trace amounts of fluoride. This ion was separated from sample matrix by distillation in the presence of sulfuric and phosphoric acids, and was subsequently determined with spectrophotometry based on the mixed-ligand complex of lanthanum(III)-fluoride-alizarin complexone. The proposed FI system has high sampling frequency (20 samplesh(-1)), small sample size (600 microl) and the dynamic range of 0.