ABSTRACT
A chromatographic and thermodynamic study of the derivatives of 4,5-disubstituted-2,4-dihydro-3H-1,2,4-triazole-3-thiones (and their Mannich bases) was undertaken. Three reversed-phase materials: a Zorbax Extend-C18, Cogent UDC Cholesterol and Regis IAM. PC. DD. 2 were studied. Plots of logk vs. the volume fraction of organic solvent in the mobile phase (φ) and the van't Hoff relationships were constructed. The van't Hoff plots revealed at least one phase transition on Cogent UDC Cholesterol and Regis IAM. PC. DD. 2. Obtained results indicated that adsorption was enthalpy-entropy driven. Cholesterol phase and Regis IAM. PC. DD. 2 in contrast to conventional octadecyl silica phase at aqueous-organic mobile phase demonstrated some liquid crystals behavior at defined conditions.