Naked-eye detection of fluoride using Zr(IV)-EDTA complex and pyrocatechol violet.

A method for the visual detection of fluoride is presented using an aqueous solution of Pyrocatechol Violet (PV), which changes its color from yellow to blue by the formation of a ternary complex with Zr(H2O)2EDTA; also, the blue color of PV-Zr-EDTA readily shifts to orange red upon the addition of a moderate concentration of fluoride. The mechanism has been interpreted by a ligand-exchange reaction of PV coordinated to Zr(IV) with fluoride. The effect of various factors, such as the pH, ratio of Zr(H2O)2EDTA and PV, and diverse ions were studied to optimize the conditions for the reaction of PV-Zr-EDTA with fluoride. The present naked-eye detection system provides a simple, quick, and sensitive method for the determination of fluoride in the concentration range 1.5 x 10(-5) to 1.5 x 10(-4) mol dm(-3). The detection limit of the method was observed to be 4.5234 x 10(-4) mol dm(-3) with a correlation coefficient of 0.9955. The developed chemosensor was applied to the detection of fluoride in industrial effluents.