Electrochemical degradation and mechanistic analysis of microcystin-LR at boron-doped diamond electrode

The electrochemical degradation behavior of microcystin-LR (MC-LR) in aqueous electrolyte at boron-doped diamond (BDD) anode was investigated under neutral pH condition. Hydroxyl radicals ((OH)-O-center dot) formed were detected by photoluminescence (PL) technique using terephthalic acid as a probe molecule, and it was observed to be predominant reactive specie. The intermediates formed in the MC-LR decomposition reaction were identified by LC-MS/MS, among which, two (m/z 1011.8 and 1029.5) were found to have multiple peaks in total ion current (TIC) chromatogram. The degradation of MC-LR was found to be mainly due to (OH)-O-center dot attack that involved hydroxylation of MC-LR via substitution/addition with a simultaneous isomerization, oxidation and oxidative bond cleavage reaction processes. The destruction of conjugated double bond of Adda was achieved by different mechanistic steps involving addition and substitution of (OH)-O-center dot that generated primary by product at m/z 1029.5. The destruction of diene bond of the Mdha, produced an adduct which was observed to be more stable, owing to a very less barrier than its substitution counterpart. (C) 2014 Elsevier B.V. All rights reserved.