Ascorbic acid was extracted with three different concentrations (1, 3 and 5 g/100 mL) of MPA and TCA. A 0.75 g of grapefruit juice was mixed with 0.75 mL of extraction solvent in a micro centrifuge tube,vortexed for 5 s and centrifuged at 4500 g (Marathon 16 KM centrifuge, Fisher Scientific, Hanover Park, IL, USA) for 10 min.