Analysis of adsorption energy distribution in selected hydrophilic‐interaction chromatography systems with amide, amine, and zwitterionic stationary phases

Abstract

Adsorption mechanisms of caffeine, quercetin, and phenol as test substances in various chromatographic systems have been analyzed. The investigations were conducted using three different chromatographic columns packed with polar bonded stationary phases, that is, amide, amine, and zwitterionic. Methanol–water and acetonitrile–water systems with different organic solvent contents have been used as mobile phases. On the basis of adsorption isotherms obtained for the tested systems, Scatchard plots and adsorption energy distributions have been determined. The most likely retention mechanisms have been discussed. The results of investigations indicate that (i) the surfaces of tested adsorbents are energetically heterogeneous, and (ii) the main role in sorption mechanism is played by low‐energy sites.

Studies on the retention behavior of quercetin, phenol, and caffeine as test substances on selected neutral and charged hydrophilic interaction liquid chromatography stationary phases

“…The presented results are in agreement with our previous statements for diol-and zwitterionictype columns [10,18]. Besides, the results of adsorption investigations presented previously in [10,11] indicate that the surfaces of all tested by us adsorbents are energetically heterogeneous, and different adsorption interactions are possible. Regardless of the mobile phase composition, this confirms the importance of a mixed retention mechanism in the HILIC process.…”

“…An important role in the retention/adsorption mechanism in various types of LC play also the interactions between liquid phase components and energetically heterogeneous stationary phase surface. For example, the results of investigations presented in [10,11] for selected systems (using four different chromatographic columns packed with diol, amide, amine, and zwitterionic stationary phases) indicate that: (i) the surfaces of the tested adsorbents are energetically heterogeneous, (ii) the main role in sorption mechanism play low energy sites. Unfortunately, the nature of these interactions is currently not fully understood.…”

Studies on the Effects of Process Conditions on Separation of B1, B2 and B3 Vitamin Mixture Using HILIC and RPLC Chromatography

“…The presence of the buffer salt in the mobile phase composition confirms its role in controlling electrostatic interactions between charged analytes and the stationary phase. On the other hand, the effect of buffer salt concentration on the retention of neutral compounds is manifested by the modification of the water layer thickness on the surface of the stationary phase [8]. The increase of the salt concentration in the case of organic phase rich eluents leads to the development of the thick water layer on the surface of the adsorbent, resulting in stronger retention due to the partition process equilibrium.…”

“…hydrogen bonding, donor-acceptor), physical interactions (i.e. dipole-dipole interactions, van der Waals forces) and hydrophobic interactions as proposed by quantitative structure retention relationships (QSRR) approach [8,9]. The final resolution on the HILIC chromatography mechanism requires further work considering the effects of the essential process parameters, i.e.…”

Studies on the Effects of Process Conditions on Separation of B1, B2 and B3 Vitamin Mixture Using HILIC and RPLC Chromatography

“…Generally, the HILIC mixed-mode retention mechanism assumes partitioning of the polar solute between the mobile eluent and a layer of the water-enriched mobile phase immobilized on the polar stationary phase [29,[33][34][35]. The separation mechanism differs from that of the RPLC and the NPLC since it may additionally involve chemical interactions (i.e., hydrogen bonding, donor-acceptor), physical interactions (i.e., dipole-dipole interactions, van der Waals forces) and hydrophobic interactions as proposed by the quantitative structure retention relationships (QSRR) approach [36,37]. The final resolution on the HILIC chromatography mechanism requires further work considering the effects of the essential process parameters, i.e., the composition and pH of the mobile phase, the buffering salt concentration, column temperature and type of applied stationary phase on the observed retention of analytes.…”