The effect of methanol and ionic strength on the reduction process of 6-benzylaminopurine
| Autoři | |
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| Rok publikování | 2012 |
| Druh | Článek ve sborníku |
| Konference | The 63rd Annual Meeting of the International Society of Electrochemistry - the book of abstracts |
| Fakulta / Pracoviště MU | |
| Citace | |
| Obor | Fyzikální chemie a teoretická chemie |
| Klíčová slova | 6-benzylaminopurine;6-BAP; HMDE;EVLS;elimination voltammetry with linear scan;LSV;linear sweep voltammetry;methanol; |
| Popis | The reduction process of 6-benzylaminopurine (6-BAP), known as an adenine type of cytokinin, was investigated on mercury electrode by DC polarography [1, 2], cyclic and differential pulse voltammetry [2]. The aim of our contribution was the study of the effect of methanol content (1-20% v/v) and ionic strength (0.1- 1 M NaCl) on the reduction behavior of 6-BAP on a hanging mercury drop electrode (HMDE). It was found that the reduction of 6-BAP on HMDE proceeds in a protonated form, and therefore the research was devoted also to the study of protonation equilibria using potentiometry. Potentiometric titration provided the determination of protonation constants (pKa). The increase of methanol concentration causes pKa decrease of 6-BAP, and a significant and non-linear influence of ionic strength on protonation equilibrium was observed. In the ionic strength range from 0.1 to 0.5 M pKa decreases, at I = 0.5 M pKa reaches a minimum, and above this ionic strength value a pKa increase was observed. Linear sweep voltammetry (LSV) in connection with elimination voltammetry with linear scan (EVLS) [3,4] allows to determine not only the reduction potentials of 6-BAP and the effect of the two above-mentioned parameters but also prediction of the mechanism of the 6-BAP reduction process. Voltammetric experiments were carried out in buffered solutions (pH 3.21) at scan rate range 100 - 800 mV/s. From the LSV and EVLS experiments it follows that the new process is indicated in more negative potentials. This new process, taking place in adsorbed state, is sensitively revealed by EVLS in the form of a peak–counterpeak signal. Finally, in dependence on ionic strength and methanol content the kinetic parameters of the 6-BAP reduction process were determined and discussed [5]. |
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