Replicate of Ascorbate curve with other chemicals

Annie

Hey!

I am new with working with electrochemistry, so choose to work with Rodeostat as it seemed good for someone like me. But I've come across some problems and I'm not sure what is going wrong.

I work with SPCE with AuNP from Dropsens, with the corresponding connector and the app to control the Rodeostat. I have tried to replicate the ascorbate concentration curve provided by your documents with other chemicals (Malonic Acid and Lactic Acid) in KCl. But none of my attempts (about 70) give me a current over 1 uA, where I expect much higher values. Some ideas what can be wrong?

Will Dickson

@Annie

Hi Annie,

A couple of quick questions:

Do you get reasonable values when running a test using the dummy cell?
Have you tried to replicate the results using ascorbate?

Annie

@Will-Dickson
Thanks for the help!

Not sure what is reasonable but by following the provided method I get.
https://imgur.com/a/askRmr7
for the different current ranges.
We did not have Ascrobate in the lab so used other organic acids.

Will Dickson

@Annie

The standard dummy cell which comes with the Rodeostat consists of a single 50K Ohm resistor. When the dummy cell is attached with the cable to the Rodeostat one end of this resistor will be connected to both the counter and reference electrodes and the other end will be connected to the working electrode. The results you should get when using this dummy cell should follow Ohm's law i.e. the measured current should be I = V/R. In your images it looks like you are sweeping the voltages from about -0.6V to 1.5V - using the cyclic test?. So your measured currents should sweep from -12uA to 30uA and back again according to Ohms law. Looking at your results this seems to be what you are getting - so I would say this first test checks out. Note, when using the +/-1uA and +/-10uA current ranges some of the currents you are trying to measure during the sweep are outside of the measurement range. Thus you are seeing saturation in the measured currents i.e. the measure values can't go above or below the limits of the ranges.

From your results with the dummy cell it looks like the Rodeostat is working correctly.

I'm not sure what is happening with the drop sense electrodes and the Malonic/Lactic Acid. We haven't worked with the AuNP electrodes or with either of these Acids.

A couple of things to check.

Make sure you are getting a good electrical connection between the screen printed electrode and the adapter. Sometimes you might need to put a thin spacer on the back of the screen electrode in order press it against the electrical connections.
Make sure the screen printed electrode is connected correctly - so that the counter, reference and working electrodes are connected to the proper connections.

Annie

@Will-Dickson

I will double check everything and hopefully everything will work.

Thanks for all the help!