I would like to help you but I need to have more information about the experimental procedure used to obtain tha attached data file and moreover do you have only one set of data?
So the experiment was done using ac impedance 5mV at room temperature in a medium of deionized water and for the ranges of 1mHz-100kh, my membrane thickness is about 80microns...did I miss anything out on the e.procedure...By the way I attached only one set of data since the others are somehow similar.
Moreover can you send me your data copied in a word page? I would need Z' Z" and frequency data. The least but not the last, which is the experimental procedure to obtain the membrane and which is the working electrode you are using?
Are you working with a three electrodes system, aren't you?Can you tell which reference and counter electrode you are using?
Send me a text (ascii) file containing imaginary, real impedance and frequency and I will have a look, I do not have the latest version of word. Regards.