I have made a solution with varying IPA and EG concentrations. when I want measure Zeta potential the software didn't have this combination. but, the result was not coming good if I select one of both. to measure this should I measure viscosity, dielectric constant and refractive index for every solution. or any other ways ?? please help.
Kuruva Harish
Only the solid / liquid disperse systems have zeta potential. Solutions of isopropnol and ethylene glycol do not characterize zeta potential.
Dear sir,
I have dispersed a semiconductor powder in this solution. but I didn't get good result.
Kuruva Harish
My first question is why do you want to measure ZP? What does it tell you when you're suspending powders in a liquid medium?
As Yuri correctly points out, zeta potential is a holistic property of particles in suspension. Usually ZP is inferred by measurement of the movement of particles in a electrical or acoustic field. If you have particles sedimenting rather than being moved by the field alone, then the results may be variable and inadequate. For a system with constant current, then you'll need conductivity in the continuous phase of about 0.001 M KCl.
As movement is measured then this can simply be quoted without conversion to a numerical ZP.
Dielectric constants are approximately additive by volume.
IPA: 18.2
Ethylene glycol: 37.0
So, assuming the volume doesn't change on mixing, a 20:80 IPA/EG mix would have a dielectric constant of approx. 0.2 x 18.2 + 0.8 x 37.0
The same is true for refractive index (since refractive index is similar to dielectric constant but at optical frequencies.
IPA: 1.38
Ethylene glycol: 1.43
Viscosity:
IPA: 1.92 cP
Ethylene glycol: 16.2 cP
Use https://profmaster.blogspot.com/2007/12/how-to-calculate-viscosity-of-liquid.html
BUT - zeta potential may be meaningless, especially at the higher IPA. The simplest zeta potential calculation just normalizes electrophoretic mobility for viscosity and dielectric constant. This is the same as applying the Smoluchowski equation. So, if your instrument lets you choose the calculation, choose it. If it offers Huckel, you can use that, too, since it is just a factor of 2/3 different. Do NOT attempt to use the Henry equation.
Certainly don't apply the usual (and misleading) rules about zeta vs. stability (>25mV stable etc).
If you are interested in stability, you should take into account the changes in the attractive forces between particles as you change the mixture. Increasing viscosity will slow the kinetics. Attraction is weaker as the refractive index of the liquid and particles get closer. But your refractive indexes only differ by 3% which is less than the reproducibility of the measurement.
Use a dip cell.
Dear Alan F Rawle sir,
I want to prepare a stable solution. so I want to check it with a mixture of solutions even though one solvent is enough .actuvallu with one solvent I am not getting good results (iam not getting +30)so I wanna check with a combination of those.
Kuruva Harish
ZP has nothing to do with stable solutions. Again, go back and read the initial responses. ZP is the function of particles in a continuous phase.
As John Francis Miller correctly points out the mantras of 25 or 30 mV for 'stability' are nonsense if they're not referring to aqueous systems. Read Riddick's Table 1 to be found on earlier discussions in RG. Size and density (of the powdered particles) may be the more important parameters in your system. Have you carried out a Stokes' Law calculation to see what sized material would quickly sediment in your system?
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