Naslov
METAL COMPLEXATION MODEL IDENTIFICATION AND THE DETECTION AND ELIMINATION OF ERRONEOUS POINTS USING EVOLVING LEAST-SQUARES FITTING OF VOLTAMMETRIC DATA

Autori
Grabarić, S. Božidar ; Grabarić, Zorana ; Diaz Cruz, Jose Manuel ; Esteban, Miquel ; Casassas, Enric

Izvornik
Analytica Chimica Acta (0003-2670) 363 (1998);

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Anodic stripping differential pulse voltammetry. Metal-ion ligand complexation model identification. Consecutive

Sažetak
The experimental errors and their propagation are very often neglected when using voltammetric data for chemical model identification, consecutive stability-constants determination and speciation studies. The influence of the experimental error has been analyzed for two mathematical models used very frequently, viz. the Leden-DeFord-Hume and the van Leeuwen mathematical models. It was demonstrated using simulated noise-free and noise-corrupted data that relatively small and usually occurring experimental errors, in half-wave or peak potential, can blur the initially assumed chemical model or can lead to a set of incorrect stability constants. In order to minimize the influence of error on model identification and parameter estimation, an evolving least-squares fitting (ELSQF) procedure is proposed which makes use of progressively increasing tin forward and backward directions) data window size. At the same time, a procedure for detection and elimination of erroneous points is introduced enabling more reliable estimation of the parameters that describe the metal-ion-ligand complexation systems. The proposed procedure was tested on experimental data of consecutively formed Pb(II) 2-hydroxypropanoates, obtained by differential pulse polarography (DPP) in aqueous solution of constant ionic strength, I=2 M (NaClO4), pH 5.7 and constant temperature, t=(23+/-1)degrees C, when investigating the influences of errors in the Leden-DeFord-Hume model. Data obtained by differential pulse anodic stripping voltammetry (DPASV) for the interaction of Zn(II) with a macromolecular ligand, the anion of polymethacrylic acid (PMA) at constant degree of neutralization, alpha(d)=0.8, and at two different concentrations of supporting electrolyte, c(KNO3)=0.04 and 0.10 M, are used to demonstrate the influence of error for the model proposed by van Leeuwen's group. In both cases, the ELSQF approach gave clear and unambiguous complexation model identification and reliable parameters evaluation with, or without detection and elimination of erroneous points.

Izvorni jezik
Engleski

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