LC-GC ONLINE COUPLING - PRINCIPLES, DEVEL OPMENTS AND APPLICATIONS

The practical achievement of the on-line coupling of liquid chromatogr aphy (LC) with high resolution gas chromatography (GC) is described, f eaturing different eluent evaporation and solute-focusing techniques a t the head of the capillary column in the GC apparatus. The respective advantages and drawbacks of each methodology are discussed but the on e, which uses partial evaporation of the effluent in the deactivated t ransfer precolumn, offers a great polyvalency whatever the volatility of transferred solutes may be. The reconcentration techniques used cal l for the cold trapping or a derived process. The equipment is modifie d in the sense of a reduction of the internal diameters of the LC colu mns, to reach a compromise between the volume of the transferred liqui d and the capacity of the capillary precolumn in the GC apparatus. Wit h this aim, the utilized interfaces are mainly the 'direct transfer-li ne' and the 'loop-type transfer-line' for which, the respective advant ages and drawbacks are discussed. Finally, examples of recent applicat ions in many fields are given.