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Medium Effects on the Stability of Terbium(III) Complexes with Pyridine-2,6-dicarboxylate

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journal contribution
posted on 07.08.2002, 00:00 by Guilford Jones, Valentine I. Vullev
Systematic investigation of the stability of mono-, bis-, and tris-terbium(III) complexes with dipicolinic acid is reported. The formation constants were extracted from emission titration data. For this purpose, a mathematical formalism for two complexation models was developed. Comparative studies were conducted by variation of the acidity of the medium (from H0 = −2 to pH = 7), the buffer composition (i.e., containing seven different anions), and the salt concentration (from 0.04 to 1 M). It became evident that elevating the pH and lowering the salt concentration were important, not only for increasing the values of the formation constants, but also for forming polynuclear Tb−DPA complexes. Inhibition of the latter phenomenon was observed when acetate or sulfate was present. The main purpose of the present investigation was to establish optimum conditions for conducting terbium(III)-mediated emission assays for bacterial endospore detection.