[moorufous]

What are your thoughts on the accurate quantification of compounds in their reduced form prone to oxidation during HPLC analysis?

I've been on the search for r-dihydrolipoic acid on the market and have found a company that claims they cannot perform a certificate of analysis due to rapid oxidation of R-DHLA back into RLA during HPLC analysis. Is that a valid claim?

I would like to independently analyze this R-DHLA since I've already purchased some, any suggestions on how I can proceed for the most accurate analysis?

[Babcock_Hall]

I cannot say whether or not the claim is valid.  If I were trying to develop an assay using HPLC, I would consider working under slightly acidic conditions, and I would try to remove metal ions, with the goal minimizing the rate of oxidation.  If you just need to know whether the compound is oxidized or reduced, I suggest using Ellman's reagent or an equivalent compound in a spectrophotometric assay.  There is an article about Ellman's reagent by Riddles in Methods in Enzymology, circa 1980.  The molar absorptivity of the chromophore produced in the assay is a little greater than 14,000.