Boron-doped diamond oxidation of amoxicillin pharmaceutical formulation: Statistical evaluation of operating parameters, reaction pathways and antibacterial activity.
The electrochemical oxidation of a commercial amoxicillin formulation over a boron-doped diamond (BDD) anode was investigated. The effect of initial COD concentration (1-2 g/L), current density (30-50 mA/cm2), treatment time (15-90 min), initial pH (3-9) and electrolyte concentration (2-4 g/L NaCl) on COD removal was assessed through a factorial design methodology. For the range of conditions in question, the first three single effects, as well as the interaction between COD and time were the most important ones in terms of mass of COD removed. Liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) was employed to identify major transformation by-products (TBPs); thirteen compounds were detected as TBPs of AMX electrochemical degradation, while several others appear in the original formulation. AMX degradation occurs though the following pathways: (i) hydroxylation mainly in the benzoic ring, (ii) opening of β-lactam ring followed by decarboxylation, hydroxylation and re-arrangement, and (iii) bond cleavage between the carbons of amino and amide groups. Furthermore, the process is accompanied by the release of several ions, i.e. nitrate, sulfate and ammonium. The antibiotic activity of AMX up to 1000 mg/L was tested against Klebsiella pneumoniae and Enterococcus faecalis reference strains; both bacteria are completely inactivated at this concentration but the activity is reduced substantially at lower concentrations. Oxidized samples still exhibit some antibacterial activity (50-60%) which is due to TBPs and active chlorine species present in the liquid phase. The latter are generated from chloride ions and enhance considerably AMX degradation rates.
Department of Chemical Engineering, University of Patras, Caratheodory 1, University Campus, GR-26504 Patras, Greece.
Zacharias
Z
Frontistis
Department of Environmental & Natural Resources Management, University of Patras, 2 Seferi St., GR-30100 Agrinio, Greece.
Maria
M
Antonopoulou
School of Environmental Engineering, Technical University of Crete, Polytechneioupolis, GR-73100 Chania, Greece.
Danae
D
Venieri
Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece.
Ioannis
I
Konstantinou
Department of Chemical Engineering, University of Patras, Caratheodory 1, University Campus, GR-26504 Patras, Greece. Electronic address: mantzavinos@chemeng.upatras.gr.
Dionissios
D
Mantzavinos
D000658:Amoxicillin; D000900:Anti-Bacterial Agents; D001895:Boron / Q000737:chemistry; D018130:Diamond / Q000737:chemistry*; D004339:Drug Compounding; D004566:Electrodes; D010084:Oxidation-Reduction; D014874:Water Pollutants, Chemical / Q000737:chemistry
D000900:Anti-Bacterial Agents; D014874:Water Pollutants, Chemical; D018130:Diamond; D000658:Amoxicillin; D001895:Boron
Antibiotics; BDD; By-products; Factorial design; Mechanism; Mineralization