Dynamic Light Scattering (DLS) technique is used to measure the particle diameter in liquid medium. If the particle or any substance which is soluble in water as well as organic solvents (partially or freely) then it affect its actual diameter in that dispersing medium. What should be the process for its analysis which I have discussed?
Hello.
This is sometimes a tricky problem. Two things you can try (no guarantee they will always work, but one or both may be feasible).
1) Try a diluent in which the particles have very poor solubility.
2) Try a saturated solution of the drug in water as the diluent. This will hopefully prevent or significantly slow down the particle dissolution (at least in theory).
Remember, no matter what you use, make sure you have a good estimate for the diluent properties (including viscosity... it is possible for it to change enough to not neglect, even with dilute solutions).
Good luck!
To add to Robert A Bellantone very god answer, you can also add a suitable surfactant that will adsorb strongly. I did this many years ago with a poorly soluble micronized drug substance. In the absence of surfactant, the drug eventually dissolved and reprecipitated. In the presence of a simple surfactant such as DTAB, no dissolution occurred and I was able to measure the particle size. Because I had used a highly ionic surfactant, I had to add some background electrolyte (0.1mM KCl(aq)) to prevent retardation of the Brownian motion.
If I will use very conc. solution of drug in water or in any non dissolving solvent in this case there will be more particle in the medium which may affect the light path and will detect aggregate instead of individual particles.
Other answer may work that suggested to use a surfactant. Definitely I shall try this.
Thank you
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