Stereoselective separation and detection of phenoxy acid herbicide enantiomers by cyclodextrin-modified capillary zone electrophoresis electrospray ionization mass spectrometry

An application of on-line coupling of capillary electrophoresis and mass spectrometry (CE-MS) to the chiral separation of phenoxy acid herbicide enantiomers was investigated. As an ionization method, electrospray ionization (ESI) is used for a CE-MS interface. Generally, nonvolatile additives in separation solutions sometimes decrease the MS sensitivity and/or signal intensity. In this study, however, heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TM-beta-CD) was used as a chiral selector and it migrated directly into the ESI interface. By using the negative-ionization mode along with a methanol-water-formic acid solution as a sheath liquid and nitrogen as a sheath gas, stereoselective separation and detection of three phenoxy acid herbicide enantiomers were successfully achieved with a 20 mM TM-beta-CD in a 50 mM ammonium acetate buffer (pH 4.6). (C) 1998 Elsevier Science B.V. All rights reserved.