A mathematical conversion of data coming from nonequilibrium and dynamic voltammetric techniques (a direct current sampled (DC) and differential pulse (DP) polarography) into potentiometric sensor type of data is described and tested on a dynamic metal-ligand system. A combined experiment involving DCP, DPP and glass electrode potentiometry (GEP) was performed on a single solution sample containing a fixed [L T ] : [M T ] ratio (acid-base titration). Dedicated potentiometric software ESTA was successfully employed in the refinement operations performed on virtual potentiometric (VP) data obtained from DC and DP polarography. It was possible to refine stability constants either separately, from VP-DC or VP-DP, or simultaneously from any combination of VP-DC, VP-DP and GEP. The concept of VP-DC or VP-DP is reported for the first time and numerous documented and possible advantages are discussed. The proposed procedure can be easily utilized also by nonelectrochemists who are interested in, e.g., the ligand design strategies.
A mathematical conversion of data from nonequilibrium and dynamic voltammetric techniques (directcurrent-sampled (DC) and differential-pulse (DP) polarography) into potentiometric, free-metal-ion sensortype data is described and employed in the study of Bi III complexes with the ligand picolinic acid ( pyridine-2carboxylic acid) (labile and dynamic metal/ligand system). A novel procedure that allows evaluation of experimental data collected at very low pH values (acid-base titration) is proposed. Software ESTA dedicated to potentiometry was successfully employed in the refinement operations performed with virtual potentiometric (VP) data obtained from DC and DP polarography, the latter being performed at fixed pH (ligand titration) as well as at fixed [L T ]/[M T ] ratio (acid-base titration). It was possible to refine stability constants either separately from VP-DC or VP-DP, or simultaneously from any combination of VP-DC and VP-DP obtained from ligand and/or acid-base titrations. The concept of VP-DC or VP-DP is employed for the first time in the study of an unknown Bi III /picolinic acid/OH system, and numerous documented and possible advantages are discussed. Five complexes of bismuth, ML, ML 2 , ML 3 , ML 4 , and ML 3 (OH) and their stability constants (as log b) 7.48 AE 0.01, 13.94 AE 0.01, 18.10 AE 0.04, 20.47 AE 0.25, and 26.65 AE 0.03, respectively, are reported at 0.5m (Na,H)NO 3 ionic strength and T 298 K. The proposed procedure can be easily utilized also by non-electrochemists who are interested in, e.g., ligand-design strategies.
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