Simultaneous determination of R-(-)-, S-(+)-baclofen and impurity A by electrokinetic chromatography.

A rapid method for the simultaneous analysis of R-(-)-, S-(+)-baclofen and impurity A, (4RS)-4-(4-chlorophenyl) pyrrolidin-2-one, by electrokinetic chromatography was established. The optimized condition was in 100mM sodium borate buffer (pH 9.9) containing 18mM alpha-cyclodextrin (CD) and 1% (v/v) ACN using a fused-silica capillary dynamically coated with polyethylene oxide (PEO), with an effective length of 56cm and an inner diameter of 50microm, hydrodynamic injection at 50mbar for 6s, temperature of 45 degrees C, applied voltage of 27kV and UV detection at 220nm. Baseline separation of all analytes was achieved within 9min (R(s)>2.7) with the migration order of impurity A, S-(+)- and R-(-)-baclofen. The method showed good linearity (r(2)>0.999 in a range of 5-50microg/mL for impurity A and 50-500microg/mL for baclofen enantiomers), precision (%RSDs<3.37%) and recoveries (100.3% for R-(-)-baclofen, 101.6% for S-(+)-baclofen and 96.1% for impurity A). Detection and quantitation limits were 10 and 30microg/mL for both enantiomers, and 2 and 5microg/mL for the impurity, respectively. The method was efficient for the determination of baclofen enantiomers and impurity A in pharmaceutical raw material and formulations due to its reliability, speed and simplicity.