I'd rather say no. The working electrode must be polarized (maintained) at a constant potential with respect to the reference electrode. Do you have a solution for this issue?

Is your lcr instrument capable of automatically scanning the frequency range?

Cornel Radu yes, you can automatically scan the frequency range. I know impedance measurements are certainly possible with this device because in many papers they achieve this (for example https://hal.archives-ouvertes.fr/hal-01276347/file/Fast%20and%20Accurate%20Determination%20of%20Olive%20Oil%20Acidity%20by%20Electrochemical%20Impedance%20Spectroscopy.pdf), however they never explain how they do it beyond simply listing the equipment and software used.

In that article the conductance is measured. This is not an electrochemical measurement, but only electrical (no redox process occurs at the electrodes). The cell has two electrodes. The same measurement can be done simply with a conductimeter capable of measuring in the range of 0.02 ... 2 microS. The conductimeter applies on the cell a voltage with a fixed frequency in the range of 50 ... 1000 Hz. This method is not precise enough, the recommended method for determining the acidity of oils is titration.

What do you want to measure? Is it really an electrochemical process involved in measurement? If so, I maintain my opinion already expressed. If not, you can measure the conductance with theLCR meter, but keep in mind that there is a simpler alternative, mentioned above.

I see that your measurements are in 0.01M PBS with 5mM Fe(CN)6 as redox probe. You need to polarise the working electrode. Look for a potentiostat.

Dear Thomas Farrow ,

If you have an electrochemical cell with two electrodes the you can bias it in a specific DC operating point and then you can measure its vector impedance using RLC meter. You need only to access the biased cell through a coupling capacitor.

While you need also tp prevent the flow the AC current from flowing in the biasing source by connecting a high inductance in series with it.

In this way you prevent the AC from entering the DC source and also you prevent the DC current from entering in the RLC meter.

This is the measuring circuit for the impedance of the cell.

Then you set the RLC meter in the right operating mode here the series R-C mode.

There are two papers which can help you much to perform such measurements:Article A distributed SPICE-model of a solar cell

Method Measuring the small signal and switching parameters of diodes

You can measure the electrodes in the same way you measure the cells except you access between the working electrode and the reference electrode.

Best wishes