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The TEAC (Trolox equivalent antioxidant capacity) assay is based on scavenging of 2,2′-azinobis-(3- ethylbenzothiazoline-6-sulfonate) radical anions (ABTS⁻). In this report we describe a modification based on pre-generation of the ABTS radical anions with a thermolabile azo compound, 2,2′-azobis- (2-amidinopropane)HCl (ABAP). This modification makes the assay less susceptible to artefacts, e.g. influence on the radical generation process. For most antioxidants tested, a biphasic reaction pattern was seen, i.e. a fast and slow scavenging rate. We evaluated application of the assay with both lipophilic and hydrophilic compounds with antioxidant capacity. Several organic solvents, compatible with water, were tested with α-tocopherol, quercetin and β-carotene. It was found that the TEACs differed in various solvents. Under standardized conditions additivity of TEACs obtained from individual antioxidants could …