A lipophilic oxygen radical absorbance capacity (L-ORAC) assay is an evaluation of the antioxidant capacity of solutions of lipophilic compounds. The concentrations of fluorescein, radical generator, and Trolox standard solutions were optimized to improve the precision of the assay. An interlaboratory study using two antioxidant solutions and three food extracts as test samples conducted in accordance with harmonized protocol demonstrated satisfactory L-ORAC measurements; the intermediate precision relative standard deviations (RSDmt) ranged from 7.0 to 16.7%, the reproducibility relative standard deviations (RSDR) ranged from 14.8 to 19.4%, and the HorRat values ranged from 1.35 to 1.78.
