because both Pt and Cu are highly conductive and less resistance. Also It have long stability and inertness.

Thanks Singh,

I completely agree with your statement but if you are trying to measure impedance of some biological feature, for instance, lipid membrane, then high conductance cab affect the properties of membrane. I will try to use Cu and then compare the results with Ag/AgCl. Do you have any experience of measuring impedance using potentiostat EIS.

@ Dear Mr. Khan

Yes I have done EIS of microbial fuel cell using autolab potentiostat at FRA mode

1) The point with a reference electrode, like the Ag/AgCl is that you don't want any current to float in our out as this can change potential of it, hence, don't use it as CE or WE. For CE and WE, you can use just an silver wire, if you absolute want to use silver. Pt or Cu electrodes work as well. If you use a disk electrode, you will have a easier time to interpret the results.

2) Impedance is very trick as measurement as the measured magnitude and phase depends on so many thing. So in order to get out anything useful, you have to use a proper setup as placement and size of the electrodes can significantly affect the measurement - which I guess is not what you want to study...

the We is the one whose chemistry you are interested

if you want to use this WE as a current collector it should have a broad " electro chemcial window"  - Hydrogen and oxygen evolution over potentials on this electrode should be high - pt is a poor choice - GC  ahs a large Electrochemical window

if you are studying biological systems better use Pt as it is inert

for cell configuration pl see the manual

depending on the cell fluid choose your RE

@Somaieh, Electrolyte is 1M NaCl, I am considering the freq range from 1 mHz to 100 KHz with input 10mV. 

My target voltage is around 100mV. Can I increase the input voltage from 10mV to 100mV during experiment? Does it affect my reading? I am trying to measure impedance of porous Silicon (PSi) device alone and later PSi with lipid membrane.

What I conclude from these posts that I have to consider platinum wire as WE, copper wire as CE and Ag/AgCl as RE.  Dr. Gustav mentioned that alternatively, I can use Ag wires as WE and CE, and Ag/AgCl as RE. I am not sure about this.

dear all

since 1973 i work on EIS

pl see my ppt

Muhammad Khan,

Please differentiate between AC signals and DC signals. 10mV of what? I do assume that it is AC you mean. In every AC experiments, there will also be a DC part, so please also describe that potential.

Always vary all the experimental parameter so you understand how they affect the results. So if you should test 10mV and 100mV signals - Yes. You should also test 5mV and 50mV and why not 200mV. The point is that you should get a feeling for what happens if you change the parameters. Plot the results in the same graph. If the system is linearized(small signals), then the amplitude shouldn't matter and you can use what ever you want. However, when the amplitude get too large, artifacts will occur because the system no longer behaves linearly. Electrochemical equipment is typically very robust and you cannot break it so just try away.

The changing the parameters also goes for the setup. Try what happens when you use the different electrodes. In some system the electrode doesn't matter, as long as there is one. If you are studying catalytic reactions, the choice of electrode matters a lot. 

Thankyou All, I was busy in fabrication of Solid State nanopore in Si and I successfully got it. Now I am turning towards EIS experiment again. I am using Ag/AgCl as working and counter electrodes and both electrodes are immersed in 1M NaCl electrolyte. Currently I am facing error of Cell to be overloaded. Current range is setup to Auto. But still am getting error. Any suggestion?

1. please check your electrical connections

2. check your reference electrode for air bubbles

3. Emery the crocodile clips , rinse with acetone and use for electrical connections

Thankyou Sir, I just downloaded your presentation from your previous comment. This will definitely help me in measuring the capacitance and resistance of nanopore chip w/o lipid membrane. 

What do you mean by air bubbles in RE? I am using simple Ag/AgCl wire as RF. 

I just clear both chambers and dried with nitrogen stream. I will repeat the procedure and update you very soon.  

ok now no problem

i am still getting overload current error. However, when i used simple potentiostat and run the experiment, I did not get any error. BUT in case of EIS measurements, I am getting the same error. 

My input voltage is 0.1mV with freq range 0.01 to 100K Hz. Current is set to auto range. Electrodes (WE, RE and CE) are simple Ag/AgCl wires. WE and RE are in same chamber and CE is another chamber. Electrolyte is simple water or 1M NaCl. 

please contact the manufacturer if you feel the EIS instrument is at fault

Instrument is not at faulty condition because it is working fine with internal cell. I have to find what's going on with external cell setup. 

Finally I overcome my problem. Experiment is running smoothly. Now I just need to setup buffered conditions and will record my readings. Problem was with positioning of electrodes and the distance between (WE+RE) and CE. Also it is recommended to place the electrodes near the aperture/pore.