As I understood from literature, to make a selectivity experiment, I should prepare a solution, which contains my target compound and some others with similar oxidation potentials. In this case, potential peak separations and amperometric response show that my electrode senses the target compound successfully and is selective…. However, some others believe that I should soak my target compound onto the electrode surface, wash it and then put the electrode in an analyte without any interfering compound. They say that my electrode can be called selective when it can soak and keep the target compound in its structure.
Now, I am confused with 2 different approaches… Do you have any idea which one should I take?
The first method was used in most literature that is closely related to analytical chemistry. Can you elaborate on the second method?
Dear friend:
In your electrochemical system well known:
1.- You can add others substances similars to your analyte or possibles interferents of your sistem, and you do the amperometry.
2.- You begin witth concentrations, 10 times more lower, up to 10 times more higher.than your analyte.
3.-If the interference appear with the adition of more interferent, you can increase the concentration up to this is statistically significative.
3.- You can use mixtures probable and after, measure the intensity of current.
4.- The interferents can act differents. You must study very well this.
The study about interferences is a part important of selectivity.
But also, the pre treatment of the electrode is important.
Regards
Thanks for responses. As I understood in analytical chemistry, the first methode is much common. And in medical studies, people usually go for second way to validate their results.
As mentioned by the others, the first route (adding interferences) is how you determine selectivity.
The second test you refer to is simply testing whether your analyte adsorbs onto your electrode. Again, this can be selective adsorbtion (just analyte), non-selective (everything) or an interference (something not your analyte adsorbs).
Adsorption is common if you are using a large-surface area material, especially electrodes prepared using nano-carbon material. It's important because (i) then you need to consider the optimum pre-accumulation required before measuring, (ii) the electrochemical product might remain on the surface, and thus effect future results, and (iii) if you're using a flow cell or measuring different samples at the same electrode, the adsorbed material can influence later measurements. But also (iv) pre-accumulation allows you to quantify tiny amounts of material in solution, because it's pre-concentrated at the electrode surface.
If you have 'selective adsorption' then in theory you can place your elecrode into a complex matrix, adsorb the analyte, transfer into a 'clean' matrix and quantify. However, this is quite a complex process and there are plenty of things that can cause issues during the process. Selective quantification in the matrix is preferred.
Leigh Aldous explained nicely, what is the mechanism behind selectivity of analyte? why modified electrode attract one analyte rather than others even have similar redox potential?
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