Rapid Simultaneous Capillary Electrophoretic Determination of (R)- and (S)-Secobarbital from Serum and Prediction of Hydroxypropyl-γ-cyclodextrin-Secobarbital Stereoselective Interaction Using Molecular Mechanics Simulation

Abstract

Secobarbital is a hypnotic sedative that is used in the treatment of preoperative anxiety and to manage elevated intracranial pressures and cerebral ischemia due to neurosurgical procedures. Stereoselective resolution is first predicted using hydroxypropyl-γ-cyclodextrin (HPGCD) - (R)- and (S)-secobarbital transient complex energy calculations using SYBYL 6.01 molecular modeling software. Separation is accomplished as predicted using 40mM HPGCD in 50mM phosphate buffer (pH 9.0), resulting in a rapid, sensitive method for the determination of (S)- and (R)-enantiomers of secobarbital from serum using solid-phase extraction, capillary electrophoresis (CE), and ultraviolet detection. The method involves extraction of both enantiomers and the internal standard, aprobarbital, from serum using C18 Bond-Elut solid-phase cartridges. The CE system consists of fused-silica capillary (52 cm × 75-μm i.d.) maintained at a run voltage of 15 kV with detection performed at a wavelength of 254 nm. The detection and quantitation limits from serum for (S)- and (R)-secobarbital are 1 μg/mL. Linear calibration curves from 1 to 60 μg of both (S)- and (R)-secobarbital show a coefficient of determination of more than 0.999. The precision and accuracy of the method, calculated as relative standard deviation (%) and percent error, are 0.35-4.48% and 0.71-8.67%, respectively, for (R)-secobarbital and 0.39-4.08% and 2.16-3.70%, respectively, for (S)-secobarbital.