Development and validation of a sensitive enantiomeric separation method for new single enantiomer drug levornidazole by CD-capillary electrophoresis

A fast and sensitive chiral capillary electrophoresis method has been developed to determine levornidazole and its enantiomeric impurity at a 0.05% level in levornidazole injection solution. Several chemical and instrumental parameters which have an effect on chiral separation were investigated, including chiral selectors, buffer composition and pH, applied voltage, capillary length, temperature and rinsing procedure. After optimizing all the effective parameters, the ideal separation conditions were 20 mM Tris phosphate buffer at pH 2.1, containing 2.0% (w/v) sulfated-α-cyclodextrin with short end injection at 0.5 psi for 5.0 s. Online UV detection was performed at 277 nm. A voltage of 30 kV was applied and the capillary temperature was kept at 25 °C. 2,4,6-triaminopyrimidine was chosen as internal standard to improve the injection precision. The total analysis time is less than 7 min, which is faster than the existing chiral HPLC method (65 min). The validation of the method was performed in terms of factorial analysis, stability of the solution, different cyclodextrin batches study, selectivity, linearity (from 2.5 μg/mL to 6000 μg/mL, y=0.0015 x+0.0304; R2=0.9999 and the residuals were randomly scattered around 0), LOD and LOQ (0.3 and 1.0 μg/mL, respectively), precision and accuracy. The proposed method was then applied to the enantiomeric purity control of the starting material and injection solution of levornidazole (0.5 mg/100 mL).