Troubleshooting on potentiostat experiments
Here are some general comments on trouble shooting that are valid for any experiment. We made this list, to enable even not very experienced users to find the sources of trouble as soon as possible to keep the frustration level for you and coworkers as low as possible.
- When you observe strange behavior, especially only a random zigzag line, first check if all your electrodes or your sensor are connected properly. Especially croc clips tend to slip of the electrode if placed unfortunately.
- Make sure all electrodes are immersed into the electrolyte solution. See if bubbles in front of electrodes are actually insulating the electrode surface.
- Check if the potential of your reference electrode is still correct. This is easily done by using a second reference electrode. Measure the potential difference between the two electrodes. After a few seconds it should be a stable value. If the other reference electrode is the same kind of reference electrode, for example two Ag/AgCl electrodes, the difference between them is supposed to be zero, if the difference between them exceeds 20 mV the reference electrode should be replaced. A good way to test reference electrodes is to put both reference electrodes in the same electrolyte and connect the electrodes to a voltmeter or multimeter.
- Maybe the working electrode is dirty and an insulating layer was formed on it. Polishing the electrode should remove any stains.
- If you suspect a malfunction of the potentiostat, check first if the LEDs light up in the correct way. The blue LED indicates the USB connection provides power and control. It should light up as soon as the EmStat is connected to the PC. The red LED should light up as soon as the cell is switched on. This usually happens when a measurement is started and the cell is switched off at the end of the measurement. The EmStat Blue has a battery symbol to indicate that it is switches on (steady green light) and also a red LED to indicate the status of the cell.
- A good way to check if the potentiostat and the cable are operating correctly is to perform the standard measurements described. Just connect the dummy cell, which was delivered together with the device, use the WE B and load the method PSDummyCell_LSV.psmethod. If this measurement does not look as shown in Figure 3.9, try to change the cable and perform the measurement again. If the problem is solved, the cable is the source of trouble. If the curve looks even with a different cable not as expected, it seems your EmStat or PalmSens is malfunctioning. Please contact email@example.com to solve this issue.
- If a higher level of noise is your issue, the solving strategies are rather numerous, but the sources for noise are also numerous. Here we describe the most successful and common methods for noise reduction.
- Your power grid is usually using an alternating current. This undulating current influences the measured currents. PSTrace and PStouch have a filter for this mains frequency. Check in the Tools menu under General Settings if the mains frequency is set correctly.
- Our environment is filled with electrical fields. Some of them are created by devices around us as side effects or in case of wireless communication on purpose. Although it is a bad idea to measure directly next to an electric arc furnace, it is usually not possible to have a workspace free of electrical fields, especially not during point-of-care measurements. A Faraday cage is usually sufficient to create a field free environment. A metal box or cage out of metal mesh is a good a Faraday cage. Even a shield out of aluminum foil can help. Place your electrochemical cell inside the Faraday cage and connect the cage to the ground lead (green) of the potentiostat. The cable delivered with your EmStat or PalmSens has an inbuilt shield and should protect your signal outside the Faraday cage. This is one of the most effective methods to reduce noise.
- Cables should not be unnecessary long, since they act as antennas for noise, but the cable delivered with your EmStat or PalmSens has an inbuilt shield and as long as you use the original cable, there is little reason to worry about cable induced noise.
- Ground your measurement equipment. The best way to connect your equipment is star shaped, that is all parts are connected with the ground at the same point. In an electrochemical lab that point is usually one small space of the faraday cage. This way earth loops that induce noise are avoided.
- Check if the contacts are corroded. If so, remove the stains, for example with sand paper.
- If you encounter problems that you cannot solve, please contact PalmSens BV (firstname.lastname@example.org).
Figure 3.9 | A typical linear sweep of the dummy cell’s WE B