HPLC Analysis of Aromatic Compounds (PAH) on Mixed-Mode and Reverse Phase Columns

Aromatic hydrocarbons are hydrophobic compounds that are well retained on any reversed-phase column, with retention primarily controlled by the percentage of acetonitrile (ACN). Buffer concentration or pH typically has little effect on their retention. However, on the Zodiac HST TH mixed-mode column, retention and separation of polycyclic aromatic hydrocarbons (PAHs) occur via a reversed-phase mechanism. Variations in mobile phase pH alter the ionization and conformation of the stationary phase, modifying its hydrophobicity and thus the interaction strength with analytes. This allows for fine-tuning of selectivity, making the method suitable for analyzing hydrophobic compounds and structural isomers when precise separation is required.