Antioxidant screening of beverages using the online HPLC-DPPH* assay incorporating active flow technology chromatography columns

The analysis and isolation of antioxidants from complex samples requires a separation step to fractionate the sample, followed by a means to measure the presence of the antioxidants. This can be conveniently achieved using liquid chromatography coupled with an on-line antioxidant assay. One such on-line antioxidant assay involves the diphenylpicrylhydrazyl radical (DPPH•), which provides a positive test for phenolic antioxidants through a decolorization of the DPPH• reagent. In this study we review typical applications involving the DPPH• assay. Then we demonstrate how this assay can be improved using recent developments of chromatography technology. The study uses coffee, a complex sample containing numerous antioxidants, to show the efficiency of the new technology. Using this new technology the need to employ large-volume mixing coils is no longer a requirement.