Examining Column Selectivity Differences Across Various L1 Designation Columns for Paracetamol EP Impurities Monograph (Oct 2025)

he United States Pharmacopeia (USP) has designations for all columns stationary phases used in the monograph methods. These designations outline the stationary phase type, i.e. fully porous or solid-core, and any ligand attachments, i.e. C18 or Phenyl to be used.1 However, beyond that no column specifics are given. With a multitude of columns that fit into the different designations, understanding that not all columns are the same is vital when selecting a stationary phase for a monograph method. This application note examines three columns that all fit into the L1 designation when analyzing paracetamol impurities. Selectivity differences between the columns are considered in relation to the impurities.