Toluidine isomers are based on toluene and differ whether the primary amine is ortho, meta or para to the methyl group. A Primesep 200 column with an ammonium formate buffer or a Primesep 100 column with sodium phosphate baseline resolves the three regioisomers. The HPLC separation uses a mobile phase of water, acetonitrile (MeCN, ACN), ammonium formate, or sodium phosphate and ultraviolet (UV) detection at 250 nm.
Isomers of toluidine were successfully retained and separated in cation-exchange mode on a Primesep S2 column. Primesep S2 column is a HILIC/cation-exchange column that can be operated in HILIC, cation-exchange, and anion-exclusion modes. Method and column are compatible with ELSD/LC/MS and UV and can be used for routine analysis of polar molecules.