Abstract
Complexes of tetravalent metal ions with chromogenic chelating reagents having only one methyliminodiacetate group ortho to OH group were examined for spectrophotometric or fluorometric determination of fluoride. Zirconium(IV) and hafnium(IV) were superior to thorium(IV) as a central metal ion. Three triphenylmethane dyes showed comparable sensitivities. Although two azo dyes had lower blank values and higher sensitivities than triphenylmethane dyes, further modification involving enhancement of solubilities is required for practical use. Zirconium(IV) complex of a new fluorescent reagent derived from sulfonefluorescein showed an increase in fluorescence intensity on the reaction with fluoride. The mechanism of this change in spectroscopic properties is discussed.
