Solvent composition effects on polar solutes with a silica—dimethyl sulfoxide—carbon tetrachloride chromatographic system

Analysis of purines and pyrimidines by mixed partition-adsorption normal-phase high-performance liquid chromatography

This paper summarizes the results in the development of mixed partition-adsorption (MPA) normal-phase high-performance liquid chromatography published in the last 10 years. The MPA normal-phase systems are an alternative approach not only to the adsorption normal-phase mode but also to the most widely used reversed-phase mode in the separation area of purine and pyrimidine derivatives. It is shown that the MPA systems are applicable in analytical practice.

Separation of purines and pyrimidines by normal-phase high-performance liquid chromatography using dimethyl sulfoxide in binary and ternary eluents

Chromatographic systems with a silica sorbent and mobile phases containing dimethyl sulfoxide have been studied. It has been established that the substitution of isopropanol by dimethyl sulfoxide in binary eluents results in a specific selectivity of the chromatographic system and shows an improvement of the peak shape for the solutes under study. When mobile phases consisting of hexane, isopropanol and dimethyl sulfoxide (solvents with a limited mutual solubility) are used, changes in retention characteristics and peak symmetry are caused by a transition from adsorption to partition sorption mechanism. The stationary liquid phase is generated dynamically in the pores of silica, even in the mobile phases not saturated with a polar component. If the phase ratio of the column reaches 0.1, partition dominates over adsorption and such mixed partition-adsorption (MPA) systems show very good peak symmetry for the solutes under study. The investigation has shown that dimethyl sulfoxide-containing MPA systems are applicable in analytical practice.

Solvent selectivity in the resolution of some regioisomeric and diastereomeric prostaglandin intermediates on silica

The possibilities of predicting the selectivity in the resolution of regioisomeric and diastereomeric prostaglandin intermediates on silica gel was investigated. A satisfactory correlation between log alpha and the solvent localization parameters m and m0 was obtained, confirming the importance of solvent-solute localization in determining alpha values. The results will be useful in developing further the theory of the selectivity of resolution.