Separation of Aromatic Carboxylic Acids by Mixed-Mode HPLC

This application using the Zodiac HST B column highlights the ease of method tuning when working with mixed-mode stationary phases. Aromatic carboxylic acids are effectively separated, and their retention times can be finely adjusted by simply varying the mobile phase modifier. Substituting between formic acid, trifluoroacetic acid (TFA), phosphoric acid, and perchloric acid in a constant water/acetonitrile (MeCN) ratio results in notable shifts in elution times—an effect not typically observed on traditional reversed-phase C18 columns. These changes arise from both the variation in mobile phase pH and the nature of the counterion interacting with the column’s embedded functional groups. This method is compatible with mass spectrometry and supports mobile phases containing water, acetonitrile, and formic or trifluoroacetic acid for LC/MS analysis.