Evaluation of antioxidative activity of some antioxidants by means of a combined optothermal window and a DPPH* free radical colorimetry

Antioxidative activities of vitamin C, BHA, BHQ and BHT oxidants were deter mined at ambient temperature by means of a DPPH* colorimetry (in methanol) combined with the optothermal window (OW) detection scheme at 514 nm. The r esults of OW-DPPH* experiments suggest differences in the reaction kinetics for various compounds; these were also found to be concentration dependent . Vitamin C reacted with DPPH* more rapidly than BHA, BHQ and BHT. Although OW-DPPH* colorimetry exhibits a dynamic range that is wider than that typi cally encountered in conventional spectrophotometry (SPM), its sensitivity is inferior to that of SPM. Search for new colorimetric reactions resulting in a more intense color yield is encouraged, if the unique advantage of OW -DPPH* method (to handle optically opaque samples) is to be fully realized.