I used Zetasizer Nano ZS to measure my polystyrene microparticles, and the data quality report suggests the zeta potential distribution is poor. I've checked the SFR spectral quality data, all of my 6 replicates for the same sample is below 1. In the technote, poor zeta potential distribution could originate from improper sample concentration, high conductivity samples, and less than enough sub runs. I've checked the derived count rate, which is 13,000-18,000 kcps with attenuator setting is 7. The sub run number is 22 for all samples. Since I saw blacking effect on the electrode after measurement, which suggests electrode degradation. Therefore, I suspect the conductivity is relatively high. However, the dispersant composition only includes 50mM Tris Buffer with some trehalose and glycerol. I'm not sure whether the monomodal will be required in this case and more sub runs will be helpful? Your answers will be highly appreciated.
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W110614ProteinZetaPotentialDiffusionBarrierMethod.html
Hi Juelu Wang , you can see the conductivity of your measurements on the Zeta Report or also listed in the Zeta workspace. Yes, it appears that you have enough scattering intensity signal. If your overall mean zeta potential is very close to zero then it may be difficult to improve the data quality. The diffusion barrier method may improve. Here are a few comments that may be useful:
on mean zeta: https://www.materials-talks.com/blog/2017/09/05/what-is-the-zeta-deviation/
on measuring in high salt (just for info): https://www.materials-talks.com/blog/2020/07/15/measuring-zeta-potential-in-saturated-ionic-strengths/
on diffusion barrier: https://www.materials-talks.com/blog/2015/11/24/diffusion-barrier-method-the-practical-details/
and finally, feel free to add a data file: https://www.materials-talks.com/blog/2014/08/19/faq-how-can-i-submit-a-data-file-to-the-help-desk/
Sonication of nano/micro materials before performing measurement is highly recommended. Further, increase the number of runs.
Omkar Singh Kushwaha Thanks for your suggestion. I checked my particle size by DLS as well, and it looks Ok without aggregation. Whether still requires sonication before Zeta measurement? Thanks.
Ulf Nobbmann Alan F Rawle Thanks for your reply. Actually, I've tried diffusion barrier techniques as suggested by the technote. Briefly, I loaded the dispersant first by using the syringe and then loaded ~50ul of my sample (microparticle in dispersant) at the bottom. However, I noticed that the microparticles didn't really all sit at the bottom after the run finished, and the derived count rate varied a lot (136-1742kcps) among repeated measurements, suggesting the sample was not stable. I suspected whether the samples were undergoing dispersion through the dispersant causing instability. Do I need to increase my sample volume by using this technique? Or do you have any recommendations? Thanks a lot!
Juelu Wang It is easier to perform the diffusion barrier method with a larger volume. The best method is to first "practice" pipetting blue dye into the (disperant-filled) cuvette, to visualize the effect of the injection and watch how the plug of blue sample may be moved even by the removal of the pipette tip. It can take a few tries to minimize the volume and then use a real sample.
Hi Juelu Wang , hope you were able to improve the zeta results of the particles. If not, please attach a data file, ideally with size and zeta results.
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