Add time:09/24/2019         Source:sciencedirect.com

Direct current and differential pulse polarography, linear sweep cyclic voltammetry, UV and fluorescence spectroscopy techniques were employed to study the reduction of 2-hydroxy-3-phenyl-6-methylpyrazine (HPMP), a degradation product of β-lactam antibiotics. The reactions associated with the reduction of this derivative are highly dependent on the pH. However, an overall process involving two electrons and two or three protons was observed.The electrochemical behaviour is clearly different in the following pH ranges: at pH < 0.6, the protonated species in solution undergoes a two-electron, two-proton electrode reaction; at 0.7 < pH < 1.8, the non-protonated species undergoes a fast protonation at the interface prior to the electrode process, yielding a protonated dihydropyrazine derivative; at 1.8 < pH < 9 the non-protonated species undergoes a fast protonation and a two-electron, one-proton reaction yielding the non-protonated dihydropyrazine derivative. Finally, at pH > 9, the above-mentioned protonation reaction slows down, leading to a kinetic-controlled process and the reduction of the non-protonated form.

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