I have made a liposome dispersion of the DPPA lipid (from Avanti Polar lipid LLC). I need to know the physical properties of this before characterizing the size and zeta potential of the dispersion. I need the absorbance and viscosity of this system
You do not need the optical properties of the particle for either a particle size distribution (by intensity) in DLS or zeta potential. You'll need the refractive index of the dispersant liquid only to correct for the refraction of the laser beam passing through the system. If you require the optical properties of the lipid (for example for conversion to volume) then measure on a Abbe refractometer. See:
June 26th, 2012 Uses of an Abbe refractometer http://tinyurl.com/lbp4szy
Note that it's the separate properties of the particle and the dispersant phase that are required - not of the system as a whole. Even if the lipid fully dissolved in water (which it doesn't) then you have a 1% solution and this will not differ much from that of pure water.
Hi,
For particle size, PDI and zeta potential measurements of liposomes:
the device is set to a medium viscosity of 1.0200 and medium refractive index of 1.335.
See attached paper for reference.
@ David Conduct a robustness test. Again you do not need the optical properties of the particle for an intensity size distribution or a zeta potential measurement.
I know but sometimes we try to use number or volume measurements. Dr Mozafari gave an interesting paper but it doesn't say the 1.335 came from.
The 1.335 comes from the minor increase in RI when a small amount of material is added to water. Read the international standards - ISO13321:1996, ISO22412:2008, ASTM2490-09(15) - all state that an intensity distribution must not be converted to number. Again, conduct a robustness test.....
You could get the info over a wide spectral range using ellipsometry.
Probably is too late for an answer, but I found the info at Malvern. Hope it is still helpfull. http://www.materials-talks.com/blog/2014/08/05/faq-how-important-are-refractive-index-absorption-for-nanoparticles/
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