Separation of vigabatrin enantiomers using mixed-mode chromatography and its application to determine the vigabatrin enantiomer levels in rat plasma.

Mixed-mode chromatography-comprising a mixed phase with reversed and ionic phases, enabling hydrophobic and ion-exchange interactions simultaneously-was applied to identify vigabatrin enantiomers by HPLC with pre-column fluorescence derivatization with 2,5-dioxopyrrolidin-1-yl (4-(((2-nitrophenyl)sulfonyl)oxy)-6-(3-oxomorpholino)quinoline-2-carbonyl)prolinate (Ns-MOK-(S)-Pro-OSu). The MOK-(S)-Pro-vigabatrin enantiomers were efficiently separated within 12 min (total analysis time per sample: 28 min, including washing and equilibrium time for the column). The mobile phase was H2O/CH3OH/10 mM ammonium formate (pH 2.0) (20/20/60, v/v/v). Column temperature was maintained at 60℃. The proposed HPLC method could successfully monitor plasma vigabatrin enantiomer levels in rats administered (±)-vigabatrin (50 mg/kg, p.o.).

Effects of derivatization reagents consisting of n-alkyl chloroformate/n-alcohol combinations in LC-ESI-MS/MS analysis of zwitterionic antiepileptic drugs.

In the current study, three antiepileptic drugs with zwitterionic properties, namely vigabatrin, pregabalin and gabapentin, were chosen as model analytes to undergo derivatization by applying various n-alkyl chloroformate/n-alcohol combinations, followed by LC-ESI-MS/MS analysis. The employment of 16 combinations per drug using methyl, ethyl, propyl or butyl chloroformate coupled with methanol, ethanol, propanol or butanol, greatly affected a series of parameters of the derivatives, such as retention time on C8 column, signal expressed via areas, limit of detection values, as well as the yields of the main and side reactions. Practically, even slight modification of n-alkyl group of either chloroformate or alcohol resulted in significant changes in the chromatographic and mass spectrometric behavior of the novel derivative. It was clearly demonstrated that all the estimated parameters were highly correlated with the length of n-alkyl groups of the involved chloroformate and alcohol. The most significant influence was monitored in peak area values, indicating that the length of the n-alkyl chain plays an important role in electrospray ionization efficiency. For this parameter, increasing the n-alkyl chain from methyl to butyl led to increment up to 2089%, 508.7% and 1075% for area values of derivatized vigabatrin, pregabalin and gabapentin, respectively. These changes affected also the corresponding values of limits of detection, with the estimated improvements up to 1553%, 397.7% and 875.0% for the aforementioned derivatized drugs, respectively. Besides the obvious utilization of these conclusions in the development of bioanalytical methods for these analytes with the current protocol, this study offers valuable data which can be useful in more general approaches, giving insights into the effects of this derivatization reaction and its performances.

A direct HPLC method for the resolution and quantitation of the R-(-)- and S-(+)-enantiomers of vigabatrin (gamma-vinyl-GABA) in pharmaceutical dosage forms using teicoplanin aglycone chiral stationary phase.

A direct chiral high-performance liquid chromatography (HPLC) method was developed and validated for the resolution and quantification of antiepileptic drug enantiomers, R-(-)- and S-(+)-vigabatrin (gamma-vinyl-gamma-aminobutyric acid) in pharmaceutical products. The separation was optimized on a macrocyclic glycopeptide antibiotic chiral stationary phase (CSP) based on teicoplanin aglycone, chirobiotic (TAG), using a mobile phase system containing ethanol-water (80:20, v/v), at a flow rate of 0.4ml/min and UV detection set at 210nm. The stability of vigabatrin enantiomers under different degrees of temperature was also studied. The enantiomers of vigabatrin were separated from each other. The calibration curves were linear over a range of 100-1600microg/ml (r=0.999) for both enantiomers. The overall recoveries of R-(-)- and S-(+)-vigabatrin enantiomers from pharmaceutical products were in the range of 98.3-99.8% with %RSD ranged from 0.48 to 0.52%. The limit of quantification (LOQ) and limit of detection (LOD) for each enantiomer were 100 and 25microg/ml, respectively. No interferences were found from commonly co-formulated excipients.

Liquid chromatographic resolution of vigabatrin and its analogue gamma-amino acids on chiral stationary phases based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid.

Racemic vigabatrin, an anticonvulsant drug used for the treatment of epilepsy, and its analogue gamma-amino acids were resolved without derivatization on liquid chromatographic chiral stationary phases (CSPs) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid. Between the two CSPs which contain 3 methylene-unit or 11 methylene-unit spacer group, the latter was found to be greater than the former in the resolution of vigabatrin and its analogue gamma-amino acids, the separation, alpha, and the resolution factor, RS, for the resolution of vigabatrin on the latter being 1.91 and 4.57, respectively. The chromatographic behaviors for the resolution of vigabatrin and its analogue gamma-amino acids on the two CSPs were found to be dependent on the type and the content of organic and acidic modifiers in aqueous mobile phase.

Capillary electrophoresis enantioselective separation of vigabatrin enantiomers by precolumn derivatization with dehydroabietylisothiocyante and UV-vis detection.

A simple and reliable capillary electrophoresis (CE) method with UV-vis detection is presented for the enantioselective separation and determination of vigabatrin enantiomers. Dehydroabietylisothiocyante (DHAIC), a novel chiral derivatizing reagent, was used for precolumn derivatization of vigabatrin enantiomers. Optimal separation was obtained with a running buffer consisting of 50 mM Na2HPO4 (pH 9.0), 17 mM sodium dodecyl sulfate (SDS) and 25% acetonitrile. The enantiomeric separation of vigabatrin derivatives was achieved within 25 min, and the resolution was found to be 2.1. Detection was followed by direct UV absorptiometric measurements at 202 nm. A calibration curve ranging from 0.3 to 6.0 microg/ml was shown to be linear, and the limit of detection was 0.15 microg/ml. The developed method has been applied to the determination of vigabatrin enantiomers spiked in human plasma, no interferences were found from endogenous amino acids.