Reversed phase HPLC with high temperature ethanol/water mobile phases as a green alternative method for the estimation of octanol/water partition coefficients.

High temperature ethanol/water was explored as a green eluent in the reversed-phase liquid chromatographic approximation of pure water retention (log k) and subsequent estimation of the octanol/water partition coefficient (log P) via the Collander equation and the Leave-One-Out method. As part of this work, linear solvation energy relationships were employed to compare the log k extrapolated systems based on high temperature ethanol/water, ambient acetonitrile/water, and ambient methanol/water mobile phases. Based on the comparisons of the three organic modifiers, high temperature ethanol/water mobile phases were observed to provide the best estimation of log P.

Characterization of the polarity of subcritical water.

The polarity of subcritical water was studied solvatochromically with betaine dye (33) across a temperature range of 30°C-180°C and a pressure range of 13.8bar (200psi) to 124bar (1800psi). It was observed that temperature has a greater effect than pressure on the polarity of subcritical water.

Retention mechanism of a cholesterol-coated C18 stationary phase: van't Hoff and Linear Solvation Energy Relationships (LSER) approaches.

This study examines the effect of temperature on the dynamic cholesterol coating of a C18 stationary phase and the effect of this coating on the retention mechanism. In general, an increase in temperature results in a decrease in the mass of cholesterol coated on the stationary phase. Typically, an increase in temperature from 25°C to 55°C results in a nearly 60% reduction in the mass of cholesterol loaded.

Stability and selectivity of a cholesterol-coated C18 stationary phase.

This paper details the use of cholesterol as a mobile phase additive and stationary phase complexing agent in reversed-phase liquid chromatography. Cholesterol loading onto a typical C18 stationary phase is examined. It is found that, when using a standard 150 mm x 4.