Capillary electrophoretic enantioselective determination of zopiclone and its impurities.
A capillary electrophoretic enantioselective method with UV detection was developed and validated for the simultaneous quantification of zopiclone enantiomers and its impurities, zopiclone-N-oxide enantiomers, and 2-amino-5-chloropyridine, in tablets. The analytes were extracted from the tablets using ACN and were separated in an uncoated fused-silica capillary (50 μm, 42 cm effective length, 50 cm total length) using 80 mM sodium phosphate buffer pH 2.5 and 5 mM carboxymethyl-β-cyclodextrin as running buffer. The analytes and the internal standard (trimethoprim) were detected at 305 and 200 nm, respectively. A voltage of 27 kV was applied and the capillary temperature was maintained at 25°C. All enantiomers were analyzed within 8 min and linear calibration curves over the concentration range of 0.4-0.8 mg mL⁻¹ for each zopiclone enantiomer, 0.8-1.6 μg mL⁻¹ for 2-amino-5-chloropyridine and 0.4-0.8 μg mL⁻¹ for each zopiclone-N-oxide enantiomer were obtained. The coefficients of correlation obtained for the linear curves were greater than 0.99. The intra-day and inter-day accuracy and precision were lower than 2% for all analytes. This validated method was employed to study the degradation and racemization of zopiclone under stress conditions. This application demonstrated the importance of a stability-indicating assay method for this drug.
Department of Physics and Chemistry, Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
Milena Araújo
MA
Tonon
Pierina Sueli
PS
Bonato
D053961:Azabicyclo Compounds / Q000032:analysis* / Q000737:chemistry; D004340:Drug Contamination; D004355:Drug Stability; D019075:Electrophoresis, Capillary / Q000379:methods*; D016018:Least-Squares Analysis; D057230:Limit of Detection; D010879:Piperazines / Q000032:analysis* / Q000737:chemistry; D011725:Pyridines / Q000032:analysis* / Q000737:chemistry; D015203:Reproducibility of Results; D013237:Stereoisomerism; D013607:Tablets / Q000737:chemistry
D053961:Azabicyclo Compounds; D010879:Piperazines; D011725:Pyridines; D013607:Tablets; C515050:zopiclone; C053228:zopiclone N-oxide; C108972:2-amino-5-chloropyridine