Hi, I am studying antioxidant activity of my plant extracts by cyclic voltammetry using ascorbic acid as standard. I have encountred a problem with voltammograms of ascorbic acid as I found two oxidation peaks but in the literature there is just one anodic peak. I don't know what is going on.
Could any one help me to explain this result. Thank you.
It will be helpful to upload your voltammogram here so that by looking at it, useful contributions can be made. Even though the mechanism of AA redox is often written to seem like two separate one electron processes, it often shows one oxidation peak. Due to homogeneous reactions of dehydroascorbic acid, there is little or no reduction peak. Please check CVs of your electrode in blank supporting electrolyte. Maybe one peak is coming from there either due to electrolyte or electrode reactions.
Thank you Prof. Gyan. Blank supporting electrolyte (phosphate buffer) doesn't show any reaction. The new peak is sharp and high, may be it is due to some degradation in my ascorbic acid?
Could you please tell me what are the best couple electrodes to carry out experiment glassy carbone/Pt wire or Pt/Pt. Most papers used glassy carbone/Pt wire, why?
Thank you again.
Carbon materials are certainly the best WEs in such analyses but the wide variety affects their performance. The narrow potential window at Pt compromises its performance with gas evolution. I would advice you to troubleshoot your setup. Change your working electrode to a 'standard' one, e.g well polished glassy carbon and maybe to another. If the peak still shows up, troubleshoot the potentiostat. Maybe it's an electronic problem. Please attach the CV to your reply. It will be easier to offer help after seeing the CV.
From my experience, sharp peaks, especially when they look like chromatographic spikes, are as a result of electrode surface contamination.
Carbon materials are certainly the best WEs in such analyses but the wide variety affects their performance. The narrow potential window at Pt compromises its performance with gas evolution. I would advice you to troubleshoot your setup. Change your working electrode to a 'standard' one, e.g well polished glassy carbon and maybe to another. If the peak still shows up, troubleshoot the potentiostat. Maybe it's an electronic problem. Please attach the CV to your reply. It will be easier to offer help after seeing the CV.
From my experience, sharp peaks, especially when they look like chromatographic spikes, are as a result of electrode surface contamination.
Carbon materials are certainly the best WEs in such analyses but the wide variety affects their performance. The narrow potential window at Pt compromises its performance with gas evolution. I would advice you to troubleshoot your setup. Change your working electrode to a 'standard' one, e.g well polished glassy carbon and maybe to another. If the peak still shows up, troubleshoot the potentiostat. Maybe it's an electronic problem. Please attach the CV to your reply. It will be easier to offer help after seeing the CV.
From my experience, sharp peaks, especially when they look like chromatographic spikes, are as a result of electrode surface contamination.
I agree with Isaiah.. plants include many phenolic antioxidants with similar peak potentials to AA.. liquid chromatography in front of electrochemical oxidation solves that problem...a uv detector can also be very helpful.. oH is important, scan rate is important, a clean electrode is important. Concentration s too high or too low can be a problem.. a picture is worth 1000 emails as Isaiah suggested.
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