Isomers are compounds with similar structures and their chemical equilibrium constant(K) is almost the same. It’s very difficult to operate chromatography separation on isomers, especially the separation of meta and para isomers on the benzene ring.
Usually, we would choose HPLC columns with steric hindrance to analysis, such as Ultisil XS-C18, Ultisil PFP, Ultisil PAH, Ultisil XB-C30.
If the columns above can not meet the separation requirements, there’s another better choice-Ultisil Chiral Column for you. Welch has four kinds of Chiral Columns: Cellu-D、Cellu-J、Amy-D and Amy-S. Here’s a case of isomer separation for Cellu-D as following:
1、Separation of ortho, meta and para isomers
Mobile Phase: N-hexane: isopropanol = 95:5
Detector: 210 nm
Flow Rate: 1.0 mL/min
2、Separation of ortho and para isomers
Mobile Phase: Methanol
Detector: 290 nm
Flow Rate: 0.8 mL/min