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 100 mM sodium borate buffer (pH 9.9) containing 18 mM α-cyclodextrin (CD) and 1% (v/v) ACN using a fused-silica capillary dynamically coated with polyethylene oxide (PEO), with an effective length of 56 cm and an inner diameter of 50 μm, hydrodynamic injection at 50 mbar for 6 s, temperature of 45 °C, applied voltage of 27 kV and UV detection at 220 nm. Baseline separation of all analytes was achieved within 9 min (R_s > 2.7) with the migration order of impurity A, S-(+)- and R-(-)-baclofen. The method showed good linearity (r² > 0.999 in a range of 5-50 μg/mL for impurity A and 50-500 μg/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 30 μg/mL for both enantiomers, and 2 and 5 μg/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.