2014 Volume 35 Issue 3 Pages 155-162
A method using micellar electrokinetic chromatography (MEKC) was developed for simultaneous determination of flavonoids in citrus fruits, which mainly consist of polymethoxyflavones (PMFs) and flavanone glycosides (FGs). Because there are significant differences in the magnitude of polarity between PMFs and FGs, it was difficult to optimize the conditions of MEKC using sodium dodecyl sulfate (SDS) for proper separation of both PMGs and FGs simultaneously. This was also found to be the case when an organic modifier such as dimethylsulfoxide (DMSO) was added to the running solutions. Simultaneous MEKC separation of PMGs and FGs was achieved by using sodium deoxycholate (SDC) in the presence of DMSO because of the relatively small difference in free energy to transfer from bulk solutions to the SDC micelle between PMFs and FGs. Fourteen flavonoids consisting of 4 flavanones, including three FGs and 10 flavones, including nine PMFs,were separated nearly completely using 10 mM phosphate buffer (pH 7.2), 75 mM SDC, 20% DMSO, and 10% acetonitrile as a running solution for MEKC. Additionally, we proposed a novel index that is an alternative to migration time and corrects variation of migration times in measurements successfully. Some of the flavonoids in fruits such as flat lemon and ponkan orange were identified with the help of this index. Further, fruit rind samples of ponkan oranges were taken monthly from a single tree from July to December and were analyzed for changes in content of four flavonoids.