Open AccessAmphoteric behavior of di-2-pyridyl ketone benzoylhydrazone in ethanol-water mixtures
Author(s) -
Ivanise Gaubeur,
Maura Vincenza Rossi,
Koshun Iha,
Maria Encarnación Vazquez Suárez-Iha
Publication year - 2000
Publication title -
eclética química
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.177
H-Index - 19
eISSN - 1678-4618
pISSN - 0100-4670
DOI - 10.1590/s0100-46702000000100006
Subject(s) - chemistry , potentiometric titration , solvent , ethanol , aqueous solution , ketone , reagent , solubility , titration , metal ions in aqueous solution , dissociation constant , inorganic chemistry , nuclear chemistry , metal , organic chemistry , ion , biochemistry , receptor
The ligand di-2-pyridyl ketone benzoylhydrazone (DPKBH) is widely used for the determination of transition metal ions in environmental samples. Due to its low solubility in water it is used in aqueous-ethanol (1:1) solvent and for higher sensitivity the pH must be properly adjusted. The properties of DPKBH solutions must be known at different ethanol-water percentages in order to achieve higher sensitivity and/or selectivity for metal analysis. The acid-base behavior of this reagent in aqueous-ethanol solvent and the dissociation/ionization constants (pK1 and pK2) of DPKBH have been determined in different aqueous-ethanol solvent mixtures (10, 20, 30 and 50 % V/V of ethanol) from potentiometric titrations at 25.0 ± 0.1° C. As the amount of ethanol increases from 10 to 30% the pK1 and pK2 values increased, but they decreased in 50% of the organic solvent. The results are correlated with the medium composition and its effects.