역상 액체 크로마토그래피에서 벤젠류의 머무름 메커니즘

Retention Mechanism of Benzenes in Reversed-Phase Liquid Chromatography

The purpose of this study is to investigate the retention mechanism. which is the key to the prediction of retention and to the systematical optimization for benzenes in reversed-phase liquid-solid chromatography. The retention data. capacity factors(k') of twelve benzenes was measured in the systems containing 75-100% of methanol and acetonitrile as organic modifiers. and PRP-l column. From the retention data, two extensive approaches are examined in order to elucidate the retention mechanism : 1) the comparison of the retention data of the solutes containing different substituents : 2) the relationship between the thermodynamic values and the retention data, i.e., van’t Hoff plots and enthalpy- entropy compensation phenomena. The retention behaviors of benzenes having different substituents. such as normal, iso. and tertiary alkyl groups. are well interpreted in both mobile phases by the liquid-solid adsorption phenomenon. which is closely related with displacement mechanism. The effect of temperature on retention is investigated by van' t Hoff plots in the temperature range of 35-55℃. The linearity(R>0.999) means that the retention of solutes is consistent in the above temperature range. From the observation of enthalpy-entropy compensation phenomenon. some conclusions interpreting the retention mechanism are drawn as follows : 1) the retention mechanism of solutes depends on the type of organic modifier in hydro-organic media ; 2) in methanol-water mobile phase. the retention mechanism of benzenes is consistent and identical in the range of 75-100% methanol-water ; 3) on the other hand. in the case of acetonitrile-water mobile phase, the retention mechanism depends on the acetonitrile composition. It means that the retention mechanism can not be explained only by a simple mechanism. Consequently. the retention of solutes is controlled by the displacement mechanism in methanol-water mobile phase. while the mixed mechanism. involving concurrent adsorption and partition phenomena. must be considered in acetonitrile-water mobile phase.