REVERSED-PHASE LIQUID-CHROMATOGRAPHY COUPLED ONLINE WITH CAPILLARY GAS-CHROMATOGRAPHY .1. INTRODUCTION OF LARGE VOLUMES OF AQUEOUS MIXTURES THROUGH AN ON-COLUMN INTERFACE

The feasibility of on-line reversed-phase liquid chromatography (LC)-capillary gas chromatography (GC) using an on-column interface was investigated. Large volumes of acetonitrile-water mixtures were introduced into a retention gap which was coated with a very thin film of Carbowax. The retention gap was tested regularly after repeated acetonitrile-water injections; its lifetime was several months. The maximum water content in the eluent must be close to that in the azeotropic mixture, otherwise water which is left in the gap after evaporation of the azeotropic mixture will distort the analysis. An acetonitrile-water mixture allows the introduction of 20-40-mu-l with an introduction speed of up to 100-mu-l/min by using the retention gap technique. This means that 1 mm I.D. LC columns can be used in on-line reversed-phase LC-capillary GC work.