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Solution Equilibria. A Unified Mathematical Treatment of Experimental Polarographic and Potentiometric Data from AcidBase and Ligand Titrations. A Polarographic and Ion Selective Electrode Study of Cd II ( N ‐(2‐hydroxyethyl)iminodiacetic acid)OH System
Author(s) -
Cukrowski Ignacy,
Maseko tombi
Publication year - 2003
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.200302728
Subject(s) - polarography , potentiometric titration , iminodiacetic acid , chemistry , titration , ligand (biochemistry) , electroanalytical method , inorganic chemistry , stability constants of complexes , acid–base titration , base (topology) , metal ions in aqueous solution , metal , analytical chemistry (journal) , chelation , electrode , ion , chromatography , organic chemistry , mathematics , mathematical analysis , biochemistry , receptor
It has been demonstrated that potentiometric and polarographic data coming from either acidbase or ligand titrations can be evaluated by the same set of equations and mathematical procedures involving mass‐balance equations written for any metalligand model, including polynuclear species. It is shown that the concept of the complex formation curves, used previously in modeling and refinement of stability constants in acid‐base titration, is of general nature and can be successfully used in polarographic and potentiometric experiments conducted as a function of pH or an excess of a ligand. It appears that the linear relationship Δ E vs. log [M], typical for potentiometric studies with ISE, holds also in the case of the study of kinetically mixed metal‐ligand system studied by polarography when the corrected shift in the polarographic signal is used. The relationship Δ E vs. log [M] applies equally to the acid‐base and ligand titration for both experimental techniques employed (potentiometry and polarography). The significance of the corrected shift is discussed and its meaning in the study of kinetically fast or slow metalligand systems is elaborated. Advantages of the acid‐base titration over the ligand titration are discussed. The generalized mathematical data treatment was successfully employed in the study of the Cd II ( N ‐(2‐hydroxyethyl)iminodiacetic acid) system. Results obtained from both analytical techniques (potentiometry with the use of an ion selective electrode, and two polarographic techniques) and analytical procedures (acidbase and ligand titrations) compare well with each other and with the literature data (the formation and stability constants of ML and ML 2 ). In addition, a new complex M(HL) was identified and its stability constant is reported.