Semi-Xylenol Orange complex of zirconium(IV) as a photometric reagent system for fluoride based on mixed ligand complex formation

Abstract

An equimolar mixture of zirconium(IV) and Semi-Xylenol Orange (SXO) reacts rapidly with fluoride ion at pH2 to cause an increase in absorbance at about 530 nm. The calibration graph was linear up to 1 × 10^–5 mol dm^–3. In a flow injection system, a detection limit (signal-to-noise ratio = 3) of 2.5 × 10^–7 mol dm^–3 was obtained with a sample throughout of 60 h^–1. Potentiometric studies of this reaction system with a fluoride ion-selective electrode demonstrated that an increase in absorbance can be ascribed to the coordination of the phenolic oxygen of SXO on the reaction of a partly hydrolysed Zr–SXO complex with fluoride ion to give the mixed ligand complex.