I am using beckman coulter counter for sizing polystyrene micro beads. Particles seems floating on the surface when added to electrolyte solution and during stirring. Can any one please suggest any dispersants to make particles well dispersed in the beaker during analysis?
While I don't have experience with that system, for small polystyrene beads you may find this post of interest: https://www.materials-talks.com/blog/2017/06/20/latex-standard-larger-than-on-the-bottle/
Hi Kavitha,
Although I haven't worked with a Coulter Counter for many years I do recognize the issue you see. The electrolyte solution depresses the electrical double layer stabilizing your particles and causes them to stick together and float. Most PS latex standards have very little surfactant in them, the stability depends on the charged groups that are the residues of the initiator to synthesize the particles.
When using these standards from a 'drop dispenser' I normally remove the stopper, and take a sample from the dispersion using a micropipette to avoid residual and clogged particles coming from the drop dispenser.
So adding a common anionic surfactant should work. I would use Sodium Dodecyl Benzene Sulphonate as both the hydrophobic tail and benzene ring have a preference for the PS particle surface. Next to that, it is very cheap and mostly available in a colloid chemistry lab.
Kind regards, Leo
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