I am trying to detect arsenic using MnOx/Au nanocomposite by LSVAS using following parameters.
Vdeposition = -0.7 V
Stripping V= -0.6 to 0.3 V
scan rate = 100mV/sec
Electrolyte: Carbonate buffer (pH = 10)
But I am not getting results specific to As in stripping scan (results attached). Also I am not seeing any peaks specific to As (III) oxidn/reduction in CV as well.
Kindly suggest.
Why are you using the regulatory system carbonate?. Is it a real sample containing arsenic? Is it a salt for a trial? You can try with other regulatory systems at different pH values. You have an essay to pH 2 or 3. Electrochemical behavior study at acidic pH of salt or arsenic sample. You must also review the bibliography to know what the graph of distribution of the different species of arsenic as a function of pH. I suggest to make sweeps from zero to negative values of potential and potential negative values. Also you can do sweeps in narrow potential intervals and windows more extensive potential in both directions.I hope these suggestions help you.Greeting
I may be wrong but I am wondering why you would even try to detect metal species under basic conditions (pH 10). My best reason for not seeing any As peaks in the CV is perhaps the As is hydrolyzed into some electro-inactive hydroxide precipitates or something like that. The redox equations for As (in both +3 and +5) oxidations states involves a proton transfer and besides, to dissolve or digest metal samples, an acidic medium is required. Like Carlos mentioned, if your carbonate is not a real sample containing the As, then please change your electrolyte medium to something acidic. The CV looks like a background capacitive window with no analyte. Once you have seen redox peaks from the CV, then you can choose the proper conditions for the deposition and stripping.
Since my materal used to modify electrode dissolves in acidic condition, hence I am working in basic condition. At this pH arsenic (III) exist as dihydrogenarsenite (H2AsO3-). My samples are not real (its prepare in lab by adding As2O3 solution (prepared in H2So4) into carbonate buffer. I am following this paper, which also used carbonate buffer for arsenic detection. I don't understand why I am not getting results.
Please suggest.
Dear Pooja. I have not forgotten you. I have been having a cold and could have read thoroughly the publication. If you want to check it, I suggest you to insist. The results are late in going out when it is begun. Do not feel conquered. The scientific investigation always is desert to the beginning. But then, it transforms in deep satisfaction. The procedure of preparation of the electrode is the key. The authors know very well what happens in ácid media., the same you have observed "the acid dissolves the electrode. I suggest you check carefully the whole procedure, bearing in mind that the authors will not write meticulously the whole procedure, for what you were meeting emptinesses. Write to me how you have realized every step in the process of preparation of the composite.Greeting
Thanks Carlos for critical comments on paper,
I do understand what you said. I did repeated whole procedure many times (at least 10 times) but the problem persists. The procedure seems very clear. I may do i one more time and let you know. For nanocomposite prepration, I am cleaning my GCE and placed it in 0.04 M h2So4 solution containing 2mM auric acid and 6 mM KMnO4 and applied Cv from 0.3 to -0.5 V (cycles 10, scan rate 10 mV/Sec)
Thereafter I cahracterized this in carbonate buffer.
-Pooja
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