Is there anyway to test for the percentage purity of whitening skincare powders?

Hello all, 

I work with a small startup cosmetic company and I'm the primary formulator. Our company is prominently into skin lightening/whitening lotion but we are finding it a bit difficult to trust the purity of our whitening powders from vendors we patronize. We've had not too good reviews from our testers and I want to know if there is a way to tests for the purity of powders like alpha arbutin and glutathaion.



  • On the chap you can do some melting point testing,
    get its optical rotation analyzed with a polarimeter
    and see if Thin Layer Chromatography can give a hint on its purity.

    For a true purity % analysis you'll need to send it to a lab that does chromatography testing.
    That can cost more than $500, if not $1000.
  • Thanks for your help Gunther. That's is a good idea on melting point testing. I try that out and post the result.

    Warmest regards.
  • PharmaPharma Member, Pharmacist
    An IR spectrometer could also work ;) .
    But melting point is a reliable and comparatively inexpensive, simple and robust method. Optical rotation only works with few ingredients so does refractory index and both may not work regarding purity testing.
    TLC can be an option if you have the know how; it's highly prone to handling errors and, though cheap and in theory simple, not to recommend for someone how has no or only basic TLC skills. A semi-automated HPTLC could be an alternative for these users but $$$.
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