HPLC analysis of antioxidants.

Qualitative and quantitative HPLC methods are described for the analysis of mixtures of twelve antioxidants. For identification of the components present, gradient elution with a convex profile from 35:65 v/v water-methanol to pure methanol is used, on a Waters 5 mum C(18) Resolve column, with an ultraviolet detector. Propyl gallate and methyl p-hydroxybenzoate cannot be separated, however. For quantitative analysis, with ultraviolet and electrochemical detectors in series, the 35:65 water-methanol mixture or pure methanol is used as the eluent, under isocratic conditions, with lithium perchlorate as supporting electrolyte. An applied potential ranging from +0.8 to + 1.7 V allows detection of all the antioxidants tested. Both modes of detection are very sensitive, with limits of detection as low as 61 pg (UV, methyl p-hydroxybenzoate) and 360 pg (electrochemistry, butylhydroxyanisole).