CHIRAL SEPARATION OF LOCAL-ANESTHETICS BY A CAPILLARY ELECTROPHORESISPARTIAL FILLING TECHNIQUE COUPLED ONLINE TO MICRO-ELECTROSPRAY MASS-SPECTROMETRY/

A novel procedure for analysing chiral compounds is described in which a capillary electrophoresis/partial filling technique was coupled on- line to micro-electrospray mass spectrometry. Enantiomers of bupivacai ne and ropivacaine were separated using methyl-beta-cyclodextrin, a no n-volatile buffer additive, as a chiral selector. To avoid introductio n of the selector into the ion source, the capillary was coated with p olyacrylamide to minimize the electroosmotic flow. Prior to sample inj ection, the capillary was partially filled with cyclodextrin dissolved in acetate buffer. When 30 kV was applied, the positively charged ena ntiomers migrated towards the mass spectrometer through the zone conta ining the neutral selector, which acted as a pseudo-stationary phase. A racemic mixture of bupivacaine and ropivacaine was successfully sepa rated and an impurity of 0.25% of (R)-ropivacaine in (S)-ropivacaine c ould be detected. (C) 1998 John Wiley & Sons, Ltd.