SYNTHESIS OF A NEW METALLOFLUORECENT REAGENT (3-CARBOXY-2-NAPHTHYLAMINE-N,N-DIACETIC ACID) AND ITS APPLICATION

A new metallofluorescent reagent (3-carboxy-2-naphthylamine-N, N-diace tic acid(CNDA)) was synthesized. Its possible application was discusse d. CNDA was stable in 1% NaHCO3 solution. The fluorescence intensity o f CNDA increased by the addition of Al, La(III) and Zn at pH 3-5 and C a and Mg at pH 10. The acid dissociation constants (pK(a)) of CNDA wer e determined by the potentiometric method. The dissociation constants of carboxylic protons of CNDA were 2.44 for pK(a1) and 3.23 for pK(a2) , and the pK(a3) of ammonium proton was 7.67. The stability constants of CNDA Ca, Mg and Zn chelate were determined potentiometrically in ac cordance with the Bjerrum's method at 25 +/- 0.2 degrees C. The stabil ity constants of CNDA Al and La(III) chelate were determined by spectr ophotometric method at 25+/-0.5 degrees C. The constitution of the CND A chelate with each metal ion was 1 : 1, and the logarithmic stability constants of Al, Ca, La(III), Mg and Zn chelate were 11.83, 5.16, 8.2 5, 3.24 and 8.26, respectively. The relative quantum yields of CNDA we re 0.04-0.05 at pH 5.0 or bellow and 0.09-0.10 at pH 7.0 or more. The relative quantum yields of the fluorescence of CNDA chelate were 0.06 (pH 3.0), 0.09 (pH 4.0) and 0.11 (pH 4.5) for Al, 0.08 (pH 5.0) for La (III), 0.10 (pH 4.5) for Zn, 0.18 (pH 7.0) and 0.27 (pH 10) for Ca, an d 0.14 (pH 7.0) for Mg. Since CNDA can react with hard acid, such as A l, La(III) and Ca, CNDA should be a useful reagent for fluorophotometr y and a metallofluorescent indicator for chelatometric titration. Usin g CNDA as a metallofluorescent indicator, the fluorophotometric titrat ion of fluoride in p-fluorobenzoic acid end dexamethasone with Al by t he oxygen flask method was performed. In titration, the recoveries wer e 99.3% or more, and the standard deviation were within 0.23%.