Analytical Sciences

Abstract − Analytical Sciences, 28(2), 159 (2012).

Method Validation by Interlaboratory Studies of Improved Hydrophilic Oxygen Radical Absorbance Capacity Methods for the Determination of Antioxidant Capacities of Antioxidant Solutions and Food Extracts
Jun WATANABE,*1 Tomoyuki OKI,*2 Jun TAKEBAYASHI,*3 Koji YAMASAKI,*4 Yuko TAKANO-ISHIKAWA,*1 Akihiro HINO,*1 and Akemi YASUI*1
*1 National Food Research Institute, National Agriculture and Food Research Organization, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan
*2 National Agricultural Research Center for Kyushu Okinawa Region, National Agriculture and Food Research Organization, 2421 Suya, Koshi, Kumamoto 861-1192, Japan
*3 National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku, Tokyo 162-8636, Japan
*4 Taiyo Kagaku Co., 1-3 Takara, Yokkaichi, Mie 510-0844, Japan
Hydrophilic oxygen radical absorbance capacity (H-ORAC) is a method for evaluating antioxidant capacities of solutions of hydrophilic compounds. In this study, we improved the original method for H-ORAC determination, and evaluated the precision of the two improved methods (methods A and B) by interlaboratory studies using 5 antioxidant solutions and 5 food extracts as test samples. An interlaboratory study of method A, in accordance with the harmonized protocol, demonstrated satisfactory performance (intermediate precision relative standard deviations (RSDint) ranging from 4.6 to 18.8%; the reproducibility relative standard deviations (RSDR) ranging from 7.0 to 21.1%, and the HorRat values ranging from 0.40 to 1.93). However, methodological problems remained, and a further improved method, method B, was thus developed. An interlaboratory study of method B by 5 participating laboratories showed better intermediate precision and reproducibility (RSDint and RSDR ranging from 1.8 to 9.4%, and from 4.4 to 13.8%, respectively), and all HorRat values for the test samples were less than 1.3, suggesting good performance for the H-ORAC measurement.