Effect of analogue ions in normal-phase ion-pair chromatography of quaternary ammonium compounds

The effect of analogue ions of ion-pair reagents in the normal-phase ion-pair chromatographic behavior of quaternary ammonium compounds is shown. Different analogue ions can have a significant impact on the chromatographic behavior of quaternary ammonium compounds. Among the ion-pair reagents investigated (sodium bromide, tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrabutylammonium bromide), tetramethylammonium bromide proves to be the most effective reagent for both reducing retention time and eliminating peak tailing. The influence of analogue ions on the chromatographic behavior of quaternary ammonium compounds correlates well with their affinity for normal-phase silica gel.