What test can differentiate between O3, H2O2, and S2O8(2-) all being present in one solution?
I have read many methods like to use KI or to use KMnO4 or Ferrous.... but in literature, all 3 oxidants react with each of KI, KMnO4 and Fe(2+)..
Anybody tried at least to differentiate between two of these 3 oxidants and succeeded in quantifying them confidently?
Please not that the solution would also include sulfate ions!
Thanks in advance.
Hallo, the intension or procedure of your work is not clear. The biggest problem is the perozone reaction. Depending on pH H2O2 reacts with O3 im milli- untill microsecond range. For insitu measurements you would need a highly-time resolution analysis. For a analysis after, you are measuring only the remaining concentration in dependence on the initial concentrations. Indigo method is well-accepted when ozone is the predominating substance.
Colorimetry first with indigo trisulfonate for the ozone, then colorimetry using titaniumoxalate for the hydrogen peroxide and finally add iodide and titrate with thiosulphate to find the persulphate concentration.
I don't think this has been combined before so you need to work with optimizing the pH and figure out if you have any interference.
Indigo may be bleached by H2O2. S2O8(2-) may be analyzed by ion chromatography.
There is probably enzymatic method for H2O2 measurement in presence of ozone. As far as I remember it is an electrode covered by an enzyme. I would look for such solution. Unfortunately, I do not have a paper on it. I read it few years ago.
The paper was devoted to formation of H2O2 from decomposition of Ozone in water in absence and presence of organic matter
I have tested the stability of indigo trisulfonate with H2O2 and HOCl in the mg/L range in tap and wastewater treatment plant effluent. In which conditions have you found H2O2 can bleach Indigo trisulfonate?
@prof Andersen. Thank you for your information. I only expressed my concern about stability of Indigo in H2O2 solution. I only noticed that ozone solution containing indigo (color) is not stable. I measured after 15 minutes to have consistent results. The color fade away after longer exposure time. But this was not further reaction with ozone. I assumed that was further reaction with H2O2 or other by-products (that needs longer exposure time). Based on your information, however, I think this should be revisited.
@prof Andersen. I have checked my lab notes. I have never used indigo in a reaction vessel. I always blew residual ozone with helium (undissolved) to a separate vessel with indigo solution. Indigo reacts slowly with ozone, but very fast with H2O2 and HOCl. I think this approach is very good for analysis of residual ozone left after the process. Another marker is terephthalate-reaction with ozone degrades the molecule; however with hydroxyl radical leads to hydroxy- terephthalate. The reaction can be observed by a fluorometer.
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