Using Teicoplanin Based Chiral Stationary Phase to Explore Temperature Effects on Enantioseparation and Determination of Chiral Sulfoxides in Rat Serum

The methylated-teicoplanin aglycone chiral stationary phase (CSP) was used for the study of the enantioseparation and temperature behaviour of a set of chiral sulfoxides ( nine different aryl methyl sulfoxides, 1-( methylsulfinyl) naphthalene and [( 1,1- dimethyl-2-phenylethyl) sulfinyl] benzene) in polar organic mode. The effect of temperature on the HPLC separation of aromatic sulfoxides was studied between 10 and 50 degrees C in methanol mobile phases with different concentration of organic modifier in mobile phase composition. The van't Hoff plots were constructed and thermodynamic data were determined from the slope and the intercept of linear van't Hoff plots for all 12 racemic compounds under the study. The van't Hoff plots (ln k versus 1/T and ln a versus 1/T) were linear for all enantiomers. The elution order ( S (+) enantiomeric form eluted first) did not reverse in the temperature range of this study. Enthalpy-entropy compensation plots of Delta H(i)vs.Delta S-i showed no significant linear correlation in methanol mobile phases used in this study. According to the enthalpy-entropy compensation plots of enantioselectivity, there is some significant linear correlation if the set of studied compounds is divided into two major groups. In order to observe the influence of temperature on retention and separation in biological matrix ( rat serum), the solid phase extraction step was performed. The limit of determination (LOQ) was calculated for all studied compounds in the methanol mobile phase containing acetic acid (17.48 mmol/L) and diethylamine ( 4,79 mmol/L). The LOQ values were in the range of 7.0-24.2 ng/mL for racemic mixtures taking into consideration the recovery (82-96%) of the extraction procedure.