Influence of Structural Differences of Dextromethorphan and its Three Metabolites on their Simultaneous Separation using Various Silica Columns with a Simple Aqueous Mobile Phase

The retention behaviors and efficiencies of the chromatographic separation of dextromethorphan (DM) and its metabolites (dextrorphan (DX), 3‐methoxymorphinan (MM), and 3‐hydroxymorphinan (HM)), on three different silica columns (Inertsil, μ‐Porasil, and Lichrospher), were compared using a simple aqueous mobile phase consisting of an organic solvent (methanol or acetonitrile) and water at different volume ratios (1∶9 to 9∶1) containing triethylamine (TEA) and acetic acid (ACH). Results demonstrated that the retention capacities for basic compounds with the same ionization conditions of the silanol group were the largest for the Lichrospher column, followed by the μ‐Porasil one, with the Inertsil column exhibiting the lowest level. Based on their physical characteristics, the larger retention capacities for DM and its three metabolites in the LiChrospher column compared to those of the Inertsil and μ‐Porasil columns may have been because the LiChrospher column has the largest surface area for inter...