Dear Lydie,

I definitely agree with the previous answer provided by Alexander.  As long as the cells tolerate ethanol then it should be possible.  Do be cautious to use the appropriate diluent dielectric constant, viscosity and refractive index in your instrument SOP.

Best regards,

Mike Bender

Hde

Dear Mike and Alexander,

Thanks for your answers. I had a try and the results obtained in ethanol are totally different to those obtained in water. I think that I have to make a correction to have the same Debye lenght but I don t know yet how to do it.

Lydie

Dear Lydie,

I agree with Mike and Alexander answers totally.  As per different zeta potential reading in different solvent system such as water and ethanol is of-course suppose to happen. As both the solvent have different viscosity and dielectric constant values, the stability of the colloid would be different, that is the basis of zeta potential as we go through the Henry equation used in electrophoretic mobility which is the basic concept of zeta potential. In this equation you would see the Henry function which consist of the Debye length which is figured out through Smoluchowski approximation. I think, the theory states us all mechanism of zeta potential. The dielectric constant for water is 80.1 and  that of ethanol is 24.5 and the viscosity are different for sure.

Hope this helps you out.

Best Regards

Mahesh Samant

Dear Lydie,

Ethanol and water have different dielectric constants. You correctly point to the different Debye lenght in these  two cases. However, have you considered applying Hückel's theory for non-aqueous dispersions instead of the Smoluchowski approximation which is only valid for aqueous dispersions?

Quite interesting the discussions here. Now, I want to measure Zeta potential in a ternary mixture with a nanoparticle dispersion, which is a more complex system. The ternary mixture comprises, say, water (20 vol.-%), ethanol (50 vol.-%), and oil (30 vol.-%), with a homogeneous dispersion of silica nanoparticles.

This would mean I have to, kind of, estimate the overall dielectric constant, taking into consideration the volume fractions of each of the constituents. I hope it works this way.

Anyway, we use the ternary mixtures to make a new class of soft materials, called bijels (bicontinuous interfacially jammed emulsion gels). (10.1002/adma.201503509)

Estimating the dielectric constant assumes no change in volume when mixed which is not true for water/EtOH:

https://ecommons.luc.edu/cgi/viewcontent.cgi?referer=https://www.bing.com/&httpsredir=1&article=1667&context=luc_theses

Zeta potential via electrophoresis requires the viscosity.

Measurement using commercial light scattering instruments (e.g., Zetasizer) requires the refractive index of the liquid. (There are non-commercial ones that do not). Again, a simple volumetric approach won't work.

However, the range in refractive index for water/EtOH 1.33 to 1.36. That's about a 2% increase which is less than the uncertainty you'll get for the electrophoretic mobility.

Oils may have refractive indices ~1.5. So this does present a problem if simple volumetric calculation is not valid. Personally, I would just assume that it is.