1989 Volume 37 Issue 5 Pages 1304-1306
A new metallofluorescent indicator (N-(2-naphthyl)ethylenediamine-N, N', N'-triacetic acid, (NEDTA)) was synthesized. Its possible applications are discussed.NEDTA was synthesized in a high yield from 2-naphthol, and was stable in NaHCO3 alkaline solution. The acid dissociation constants of NEDTA determined by paper electrophoresis and potentiometry, were 2.2±0.1 (pKa1), 3.95±0.1 (pKa2), and 9.21±0.01 (pKa3). The fluorescence of NEDTA was quenched by various metal ions and NEDTA was proved to be useful as an indicator for fluorophotometric titration. Using NEDTA as a metallofluorescent indicator, 5 μmol of Cd, Cu(II), Fe(III), Hg(II), Pb(II) or Zn at pH 4 to 6 or 5 μmol of Cd, Cu(II), Hg(II), Ni(II) or Zn at pH 9 to 10 was titrated with ethylenediaminetetraacetic acid (EDTA), and back titration with Zn was performed for 5 μmol of Al, Ni(II) or Th(VI) at pH 4.6. In every titration, the coefficient of variation and the error were within 0.6%.
