Electrical Double-Layer Effects and the Origin of Indirect UV Detection in the Liquid Chromatography of a Cationic Sample Using a Cationic Probe.

Two cations, tetra-n-butylammonium (TBA(+)) and (4-nitrobenzyl)trimethylammonium (NBTA(+)), are simultaneously sorbed on the bonded phase sorbent Partisil-10 ODS-3 from water at various ionic strengths. The non-UV-absorber TBA(+) is thought of as the sample ion and the UV-absorber NBTA(+) as the probe ion in an indirect detection system. In the sorbed state, the two ions reside at different charge planes:  NBTA(+) is very close to the ODS-water interface, and TBA(+) is about 11 Å deeper into the ODS phase.

Electrical double-layer models of ion-modified (ion-pair) reversed-phase liquid chromatography.

Stoichiometric models of ion-modified reversed-phase liquid chromatography are based on chemical equilibria between ionic modifiers and analyte. These are briefly discussed. Non-stoichiometric models portray the ionic solute as being under the summed influence of all of the ions in the system.