Separation of Optical Isomers in Capillary Chromatography Using a Poly(tetrafluoroethylene) Capillary Tube and an Aqueous–Organic Mixture Carrier Solution

Capillary chromatography for the separation of optical isomers was developed using an untreated poly(tetrafluoroethylene) capillary tube and a water–hydrophilic/hydrophobic organic solvent mixture as a carrier solution. The open tubular capillary was 110 cm in length (90 cm effective length) and 100 μm in inner diameter. The carrier solution was prepared with a water–acetonitrile–ethyl acetate mixture (15:3:2 volume ratio) containing 1 mM β-cyclodextrin. A model analyte solution of dansyl-DL-methionine was injected into the capillary tube by a gravity method. The analyte solution was subsequently delivered through the capillary tube with the carrier solution by a microsyringe pump; the system worked under laminar-flow conditions. The analytes were separated through the capillary tube with on-capillary detection by an absorption detector. D-Isomer and L-isomer were eluted in this order with the water-acetonitrile–ethyl acetate carrier solution including β-cyclodextrin.