The Zetasizer software has an integrated solvent builder function, where you can select the components of your buffer and then the correct refractive index, viscosity and dielectric constants will be automatically calculated for any temperature selected during the setup of the experiment.

In recent software versions, there should also already be a pre-defined entry called ICN PBS Tablets. The values for 25C are viscosity of 0.8882 cPoise, refractive index of 1.33 and dielectric constant of 79.0 .

http://www.materials-talks.com/blog/2011/08/04/getting-ready-for-a-zetasizer-demo/

http://www.materials-talks.com/blog/2015/03/09/how-to-get-the-latest-software-for-the-zetasizer-nano/

https://www.researchgate.net/post/what_is_the_dielectric_constant_and_viscosity_of_Phosphate_buffered_saline_pH74_and_room_temperature

Dear Ulf,

Thank you for the reply.

Badrul

Dear Ulf,

Is it possible to measure (rheometer, viscometer) the viscosity of the said dispersant and used the value in Zetasizer analysis?

Thanks.

Badrul

Dear Ulf Nobbmann , I have the same problem and looking for the constants for my Tris buffered saline TBS pH 7.5 (it's 50mM Tris, 150mM NaCl). My question is now, how should I select the amount of my HCL in the program, which I use to adjust the pH to 7.5? Is there an easier way then looking for the Volume which I use for adjusting?

Thanks for your reply and your help!

Just use the values for water. The uncertainty in the measurement will far exceed any error in the values.

John Francis Miller unfortunately I need the values for TBS because otherwise by measuring the zetapotential, it will show me no standard deviation.

@Kris Paul - please explain what you mean. It doesn't make sense to me.

John Francis Miller The amount of salts in my medium/buffer affects the measuring of Zetapotential. If I measure the zetapotential of my liposomes in TBS (with Values of water), I got a value for zetapotential (but no standard deviation (SD) of zetapotential for this value). Also the software shows me no graph/peak at all. So I am not sure, if the value of zetapotential is the "true" valid value.

By measuring Nanoparticles in water, the software shows me a graph with a peak for Zetapotential and also a SD for zetapotential, that is why I am a little bit confused with my results for liposomes (I can not measure my Liposomes in water because of the osmotic process which will destroy my lipsomes).

Feel free to answer me in a personal message, I am thankful for any advice or explanation, if my thoughts are wrong.

At 150mM NaCl, the instrument will default to what Malvern call "monomodal mode" which is just another way of saying it will use only the phase analysis light scattering (PALS) calculation method to determine electrophoretic mobility. This is due to the high salt concentration and, thus, high electrical conductivity of the liquid. The peaks can only be obtained using the laser Doppler method and no commercial instrument is capable of doing that at the high conductivities you are trying to measure. It is possible, just not commercially available.

Because of the way commercial manufacturers have implemented PALS, only a single value is obtainable from a given measurement. The very first PALS instrument was capable of giving an indication of the standard deviation from a given measurement (i.e., not based on multiple measurements). Why that wasn't implemented still baffles me :)