Application of different chemometric strategies to voltammetric and UV-vis spectroscopic data to obtain a complexation model: study of the Cu(ii) binding with the phytohormone 6-benzylaminopurine

Abstract

The complexation processes of Cu(II) by the phytohormone and the possible antitumoral agent 6-benzylaminopurine (BAP) were studied by Differential Pulse Polarography (DPP) and ultraviolet-visible spectroscopy (UV-vis) in combination with chemometric programs such as Multivariate Curve Resolution by Alternating Least-Squares (MCR-ALS) and Gaussian Peak Adjustment (GPA). All data confirm the formation of the predominant 1 : 1 and 1 : 2 Cu(2+) : BAP complexes. The corroboration of the presented stoichiometries was performed by ElectroSpray Ionization-Mass Spectrometric (ESI-MS) experiments of the Cu(II)-BAP system at different ratios.

Photochemical Redox Reactions of Copper(II)–Alanine Complexes in Aqueous Solutions

“…UV–vis absorption spectra data were analyzed with multivariate curve resolution-alternating least-squares (MCR-ALS), one of the current chemometric techniques used for the analysis of spectrophotometric data and the resolution of the different species present in multiequilibria systems. − The homemade program for the MCR-ALS algorithm was implemented in Matlab (Mathworks Inc., version R2009b). Molar absorptivities (ε i , M –1 cm –1 ) at a given wavelength for individual species reported here were determined as ε Cu(II) = prefix∑ italici ε i f i where ε Cu(II) is the experimental Cu(II)-based molar absorptivity and f i is the equilibrium fraction of the total copper present as the i th complex (e.g., f CuL ≡ [CuL]/​[Cu(II)] T , f CuL 2 ≡ [CuL 2 ]/​[Cu(II)] T , f in ≡ [Cu(II)] in /​[Cu(II)] T , where f in represents the fraction of all forms of inorganic Cu(II) species).…”

Parametric Signal Fitting by Gaussian Peak Adjustment: implementation of 2D transversal constraints and its application for the determination of pKa and complexation constants by differential pulse voltammetry

“…Complexation measurements of Zn(II):oxalate, Cu(II):BAP, and Cd(II):1,10-phenanthroline systems were done according to previous experiments. 9,13,15 Voltammetric measurements of pH titrations (from pH 2.5 to 10) of PC 2 and the Cd(II):PC 2 systems were respectively done following published procedures. 8 The determination of pK a values was done in captopril drug solution in Britton-Robinson buffer adjusted to 0.1 mol L À1 ionic strength by adding KNO 3 for pH values ranging from 1.7 to 11.8 and 25 C. Solutions were deaerated with nitrogen and a scan by differential pulse polarography (DPP) was recorded.…”

“…These behaviors caused a dramatic loss of linearity that was studied and solved by GPA. 13 The rst complex (component 2) exhibits a great reversibility while the second complex (component 3) seems more irreversible.…”

“…GPA was successfully applied to the study of different complexation systems. [10][11][12][13] Furthermore, a more sophisticated function (asymmetric logistic peak) was implemented to the PSF methodology to deal with highly asymmetric signals. 14 Nevertheless, the advantage of PSF methodology is compromised by the lack of a clear link between the successive voltammograms of an experimental dataset, which are tted independently (except for the fact that the parameters optimised for every voltammogram are used as initial estimations in the tting of the next one).…”

MCR-ALS of voltammetric data for the study of environmentally relevant substances

“…Finally, the complexation processes of Cu(II) by the phytohormone and possible antitumoral agent 6benzylaminopurine (BAP) were also considered through DPP measurements [40].…”