Dear Amenah Albarudi ,

can you show, please,

1)some of your graphs,

and

2)a draft photo of your cell ?

Ioannis Samaras thank you for your reply, i will attach the graphs and a picture of my setup.

Dear Amenah Albarudi ,

try to correct the phase angles from degrees to radians[1].

So, the Zreal becomes normal (positive)[2,3].

Also, can you (re)show, please, a new draft photo of your cell (in zoom) in order to see better (what are) your electrodes ?

1. one degree is equivalent to π/180 radians: z(real)= Z*cos(theta), z(imaginary)= Z*sin(theta).

2. Quot. (Amenah Albarudi) "when i try to calculate the real and imaginary impedance to plot, i’m getting negative signs for both and the plot looks weird."

3. See the 2nd graph (in "Zcorr 'EIS-A,Albarudi'.jpg").

Dear Amenah Albarudi ,

I add the corrected graph[3].

3. Zcorr 'EIS-A,Albarudi'.jpg

Ioannis Samaras thank you so much for your help. I really appreciate it.

I have fixed the calculations for real and imaginary impedance. I will attach the new excel sheet, drawn bode, and Nyquist plots.

the Nyquist plot still looks weird, as I understood, the radius of the semicircle is related to the magnitude of impedance, therefore, bigger circles mean higher impedance. however, in my Nyquist plot, the PBS has a bigger circle than distilled water.

I am using Metrohm Dropsens electrodes G-IDEAU10, unfortunately, I don't know the exact purity as it wasn't mentioned by the manufacturer. the electrode is sandwiched between 2 PDMS sheets that are plasma bonded with a cutout where the electrodes are.

again, thank you so much for your help and time!

Dear Amenah Albarudi,

could you try to measure/check the same but EMPTY cell, e.g. without any liquid, at least in the high(er) freq. band ?

dear Ioannis Samaras sorry for the late reply.

I was able to measure the impedance in the same frequency range 500Hz-250KHz and the impedance was stable throughout the frequencies at 714.136 ohms and -0.245004 degree phase angle.

in the past week, I tried to measure the impedance of 0.1mg streptavidin magnetic beads in 0.1mM PBS, and the impedance of the same beads bonded to a biotinylated peptide. I recorded the impedance for both and the impedance for the bounded beads was significantly lower than just the beads. in literature, when peptides bind to magnetic beads the impedance should increase that's why I'm confused. the peptide has a charge of +2, is that the reason? could you share your insight on this matter? I appreciate your time and help, thank you so much!