An on-line HPLC-FRSD system for rapid evaluation of the total antioxidant capacity of Citrus fruits

An on-line high performance liquid chromatography-free radical scavenging detection (HPLC-FRSD) system was developed for rapidly evaluating the total antioxidant capacity (TAC) of Citrus fruits. With the system, all samples can be analyzed within 5 min. The on-line HPLC-FRSD system has low limits of detection (0.001–0.010 mg mL−1) and quantification (0.005–0.020 mg mL−1), excellent recovery rate (90.44–115.72%), stability (RSD < 15.80%), reproducibility (RSD < 2%), and precision (RSD < 2%). Using a guard column instead of an analytic column, this new on-line HPLC-FRSD system performed better than the existing on-line HPLC methods in the analysis of the TAC of Citrus. Compared with the conventional off-line 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzthiozoline-6)-sulphonic acid (ABTS) radical scavenging methods, our newly developed system is faster and more robust. The methodology can be a good alternative for analysis TACs of Citrus fruits and potentially for other plants and plant-based products.