EFFECT OF SURFACE MODIFICATION AND MOBILE PHASE-VELOCITY ON THE PERFORMANCE OF PARALLEL CURRENT OPEN TUBULAR LIQUID-CHROMATOGRAPHY

The role of the mobile phase velocity in the stability of the flowing retentive film in parallel current open tubular liquid chromatography (PC-OTLC) is shown. Criteria for optimization of the solvent pair indicates that, from the solvents examined, cyclohexanol represents the best choice for the retentive liquid when an aqueous mobile phase and reversed phase PC-OTLC (RP PC-OTLC) are considered. Several procedures for capillary internal surface modification were compared with the aim to optimize the performance of RP PC-OTLC using the cyclohexanol/water system. From the examined methods of modification, persilylation with octadecylcyclotetrasiloxane (D4 reagent) gives the optimum which enables retention close to theory.