As part of support of support of ZP’s products this week we are trouble shooting 501 screen printed carbon electrodes.
Key Points from the Video:
- User’s Setup & Problem:
- Using ZP 501 screen-printed electrodes (circular carbon electrodes with a large counter electrode).
- Running CV with 5 mM ferricyanide in ~0.05 M KCl (diluted from 0.1 M KCl).
- Observing distorted CV curves with unusually high currents (~100 µA vs. expected ~25 µA).
- Suspecting a bad connection or adapter issue.
- Speaker’s Analysis:
- The peak currents are ~4x higher than expected.
- Suggests the working and counter electrodes may be swapped (since the counter electrode is large, swapping would increase the effective working electrode area, leading to higher currents).
- IR drop (voltage drop due to solution resistance) worsens with higher currents, distorting the CV.
- Demonstration & Fix:
- The speaker runs a similar experiment with correct connections, getting expected currents (~25 µA).
- Recommends checking electrode connections (working vs. counter).
- Mentions that ZP potentiostats have foolproof connectors to prevent such issues.
- Other Possible Factors:
- Lower KCl concentration (0.05 M vs. 0.1 M) increases solution resistance.
- Electrode cleaning (using 0.01 M H₂SO₄) is good practice but not the root cause here.
Suggested Solutions:
- Verify electrode connections (ensure working, counter, and reference are correctly assigned).
- Check potentiostat setup (some devices auto-detect connections, reducing errors).
- Use higher electrolyte concentration (0.1 M KCl) to minimize IR drop.
- Ensure good contact between the connector and screen-printed electrodes.
Final Thought:
The distortion likely comes from miswired electrodes (working and counter swapped), not just a bad connection. Fixing this should normalize the CV shape and current magnitude.
