Actually, the Zeta potential measurement instrument (Zeta Sizer, DLS method) needs the refractive index and absorbance values of the hydrogel beads. How can I measure these two parameter values for the solid hydrogel beads? Is there any other method to measure the Zeta potential values other than this DLS method (without measuring the refractive index and absorbance)? Please, help me with some suggestions if you can. Thank you in advance.
For zeta potential (not DLS), you only need the refractive index of the medium, not the particles.
For DLS (i.e., for particle size estimation), you need the refractive index and absorbance *if* you want to use the calculation methods that yield distributions. For the cumulants method (which gives the z-average and polydispersity index), the refractive index and absorbance are NOT required.
@John Francis Miller Thank you very much for your answer, sir. I want to measure the zeta potential of polystyrene particle (50 nm) and hydrogel beads (500 um), both are suspended in water. So, as per your answer, only RI of water will be required to measure the zeta potential by the zetasizer instrument.
Please suggest me, are there any parameter needed to maintain for the measurement like amount of solid, ph of water, or anything? I am going to use deionized water supplied by Sigma.
The zeta potential will very likely be pH-dependent so you need to measure the sample without deliberately changing the pH to something other than what it is in its intended state.
For the solids content, try to be consistent from sample to sample.
Instead of deionized water, you should have some electrolyte present. e.g., 10-5 molar KCl. This ensures that the double layers around the particles will be well-defined. Furthermore, the Zetasizer (not necessarily other instruments) will complain of insufficient electrical current if using deionized water.
Thank you very much, Sir, for your great help. I will try it first as per your suggestion and inform you if any problem faced again by me. Thank you once again.
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