Dear Scientists,
Recently, I have faced with a problem and would like to ask you for some help. I am using Malvern Zetasizer for measuring the zeta potential of nanoparticles. But, I have noticed that for some nanoparticles the standard deviation is very high. What could be the reason? Also, I would like to know whether the concentration of nanoparticles affects the zeta potential or it is independent of concentration? The last question is about measuring the zeta potential in PBS compared to water for the same nanoparticles at the same concentration and would like to know the effect of solvent on zeta values.
Many thanks in advance
To be able to answer you effectively, please post the corresponding .dts files for your measurements. There are a number of possible explanations but seeing the data files will make it easier to identify the likely cause. I (and some others on RG) can open .dts files.
Regarding particle concentration - it depends. You should determine that experimentally.
The Zetasizer will struggle to give reliable quantitative results in PBS buffer. You may get results that appear okay but you should treat them with caution. This is primarily due to the choice of metal used to make the electrodes in both the fold capillary cell (gold) and the dip electrodes (palladium).
S.M.Ali Dadfar
I assume by 'high SD' you mean 'high standard deviation'. A high (please define what you mean by 'high'. Up to 10% could be considered 'normal') SD means that the sample is changing in some manner during the experiment. The source of this change needs to be found. Without knowledge of your system it's impossible to be specific. Some reasons for the sample changing could be: sedimentation, incorrect dilution resulting in destabilization of the system, cooking of a protein (denaturation), non-optimal experimental conditions, and so on. Verify the system with the transfer standard; contact your local support (Malvern Panalytical GmbH is fantastic). As John Francis Miller states please provide the .dts file where specific comments can be made rather than those of a general nature.
You may upload an example for better help. In general, high SD in zeta potential may reflect that the concentration/ions count is high.
for the 2nd Q. ''I would like to know whether the concentration of nanoparticles affects the zeta potential or it is independent of concentration?'', zeta potential depends strongly on the concentration and you should determine it using a suitable count (200-400 is optimum).
For the last question which is ''about measuring the zeta potential in PBS compared to water for the same nanoparticles at the same concentration and would like to know the effect of solvent on zeta values'', the zeta potential depends strongly on the nature of the dispersed medium, the pH, the concentration of the ions, the viscosity ... all of them affect. purified water has nearly no ions but PBS has many salts which affect the charge. It should be noted that zeta potential is a reaction, not an action, the more the ions in the buffer, the more the zeta potential value will be affected. As it is the total outer surface charge, not the actual charge.
Find the attachment, I think it will be useful.
Hello S.M.Ali Dadfar ,
for some guidance on zeta deviation check out https://www.materials-talks.com/what-is-the-zeta-deviation/ and https://www.materials-talks.com/zeta-deviation-larger-than-the-mean-how-can-that-be/
Zeta is a complex system property, this dependent on the whole composition of the sample. As an example, with ionic strength values change typically such, that absolute values are larger at lower ionic strength, see https://www.materials-talks.com/zeta-potential-in-salt-solution-or-any-other-ions/
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