I m going to check the zeta potential for alginate beads (hydrogels with a size of 1 mm diameter)by surpass 3 (with cylindrical cell) but in high pressure (600 or 500 on rinse process), my samples are gone from the measuring cell and disperse in the solution. However, I use a filter and fix the shaft tightly. I,m adjusting the permeability index at 100 by tightening the adjustment screw.
does anybody has some experience with this device?
Hi Faeze, there are a few things you could control to help you analyze these sample:
1. The cylindrical cell used in SurPASS 3 is appropriate to measure fabric/fibers, granular samples and powders. It is important that the permeability index (PI) stays at 100 +/- 20 (i.e., from 80 to 120). For fiber samples, you can adjust the PI by tightening more or less the knob of the cylindrical cell. However, for samples like yours that can easily break, the recommendation is to use the powder sample holder. You do not need to tightening the knob in this case and the PI will depend on the amount of sample you use:
- For low PI, the packing density is too high, so lower amount of sample has to be used;
- For high PI, the packing density is too low, so larger amount of sample has to be used.
You do not need to compress the sample and remember to use the filters on the bottom and on the top of the sample. You can adjust the target PI during the rinse cycles.
2. Then, you need to control the linearity of the voltage with the pressure drop. This is an important feature for the calculation of a meaningful zeta potential. In this case, it is recommended to first do an "alignment" where you check where the linear behavior starts. The standard suggestion is to use the higher pressure = 600 mbar, lower pressure = 200 mbar, and using the advance measurement options to set the upper pressure limit at 450. You can always change these parameter and it will depend on your sample. In the picture attached as an example, you could set the upper pressure limit at 400 to be sure you are taking the linear behavior.
3. Finally, when you have the PI in the desired range, and the linear behavior of the voltage/pressure is observed, you could do a time dependence measurement, i.e., several zeta cycles to understand if the PI or the ZP changes over time. This is important to check the stability of your samples in the conditions of the experiment.
I hope I could help you with the questions. Good luck!
For general sample mounting instruction with the cylindrical cell of the SurPASS 3, you can also check this tutorial video: https://www.youtube.com/watch?v=7qO8TBnxJzw&list=PLVPW8NM5rINLjgJOovr9u9-6g_1NRzYZp&index=18
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