QUANTITATIVE STUDY OF RETENTION PROCESSES IN REVERSED-PHASE LIQUID-CHROMATOGRAPHY BY MEANS OF REACTION-KINETICS

Degrees of deviation from idealized partition and adsorption retention mechanisms are quantified for reversed-phase liquid chromatographic (RPLC) columns. Rate constants for an in situ chemical reaction were measured in octylsilyl and octadecylsilyl bonded stationary phases with a methanol mobile phase. The retention behavior of several types of relevant solute molecules was investigated as a function of chain length and column temperature. With a bonding density of 2.7-3.0 mu mol/m(2) on the same support (Beekman Ultrasphere at 200 m(2)/g), the chain length (C-8 vs. C-18) does not appear to impact the retention process, suggesting similar stationary phase characteristics and compositions. However, increased temperature tends to shift retention behavior toward adsorption. The degree of hydrocarbon ligand participation in retention and the phase ratio were also determined to provide a more complete description of the stationary phase composition in RPLC.