Hi Ezzaldein,
The question here is more calculating the sensitivity TOWARDS an analyte. For example, if you want to know the sensitivity of the electrode towards hydrogen peroxide and you wanted to use chronoamp, you could simply make a calibration curve. Assuming you know the redox potential of your species (for example, 500 mV vs. Ag/AgCl), you could apply a potential and measure the current over time for different standard solutions of your analyte.
In other words, make the following measurements:
Apply a constant potential and measure the current for 30 seconds for the following solutions:
1 - Blank (i.e. background electrolyte)
2 - Standard analyte solutions (ex: 1-100 uM)
Plot the average current over 30 sec vs. concentration of your analyte
The slope of this calibration curve (assuming it is linear) is equal to the sensitivity of your electrode towards this analyte.
As a side note, it is often useful to define the sensitivty as current density response vs concentration. In other words, divide the current you measure by the area of the electrode to get current density, which makes it easier to compare to other sources afterwards.
Hope this Helps!
David
Hi Ezzaldein,
The question here is more calculating the sensitivity TOWARDS an analyte. For example, if you want to know the sensitivity of the electrode towards hydrogen peroxide and you wanted to use chronoamp, you could simply make a calibration curve. Assuming you know the redox potential of your species (for example, 500 mV vs. Ag/AgCl), you could apply a potential and measure the current over time for different standard solutions of your analyte.
In other words, make the following measurements:
Apply a constant potential and measure the current for 30 seconds for the following solutions:
1 - Blank (i.e. background electrolyte)
2 - Standard analyte solutions (ex: 1-100 uM)
Plot the average current over 30 sec vs. concentration of your analyte
The slope of this calibration curve (assuming it is linear) is equal to the sensitivity of your electrode towards this analyte.
As a side note, it is often useful to define the sensitivty as current density response vs concentration. In other words, divide the current you measure by the area of the electrode to get current density, which makes it easier to compare to other sources afterwards.
Hope this Helps!
David
In principle this approach is ok. However, some additional remarks seem to be necessary. We realized that the sensitivity of a Pt-microelectrode for e.g. H2O2 shows different values when You compare chronoamperometric measurements with cyclic voltammograms. The reason is the following: If You stay at a fixed potential (here 650mV), the adsorption layers at the surface of the electrode somehow prevent "sensitivity", which is not the case, if You cycle with the potential, e.g. from -100mV up to 1V and back. At the negative potential the surface of the electrode is "cleaned" and the sensitivity for Your substance to be tested is significantly increased. Try it!
Monika
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