How to destroy an emulsion to determine water content

Hi all,

I am trying to recreate some formulas (emulsions) on the market and I think a good first step would be to determine the water content, which should give me a good idea of the oil content. I thought of a couple methods that I am currently trying on some know formulas to see if they work:

1. Heat/distillation, up to 100C
2. Centrifuge

I also thought I'd check in with this community to see if there are better ways. The problem I see is that if I have a stable formula (and I do), they should be good at preventing the separation to occur in the face of high temperature and centrifugal force. Is there a more clever way to destabilize an emulsion? Salting out? Freezing? What would you do?

Thanks!

Comments

  • BobzchemistBobzchemist Member, PCF student
    % Volatile substance test. (or use a moisture balance)

    Without a moisture balance, this is the procedure:

    Precisely weigh out a gram or two of the test substance into an aluminum weigh dish.
    Place into oven at 105C - 110C / 220F  - 230F constant temperature.
    Check weight every half hour. When the weight has stopped changing (2 consecutive weights the same), you're done.
    The math involved in figuring out %loss is left as an exercise for the student. :)
     

    Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
  • BobzchemistBobzchemist Member, PCF student
    Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
  • BobzchemistBobzchemist Member, PCF student
    There's also a chemical titration:

    Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
  • BobzchemistBobzchemist Member, PCF student
    Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
  • Thanks Bob. I've used %volatile substance on inorganic materials to determined hydration/water of constitution. I guess my concern here is that many of these organics have vapor pressures much higher than inorganics. This is obviously quite dependent on the particular formula, but can you comment on how accurate this is in your experience with cosmetics?
  • For simply knocking off a formula, a "% solids" test (what Bob just described) is more than adequate to give you a starting point.
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