Sampling device and its use for controlling sample introduction in microcolumn separation techniques

A sampling device comprising an electrolyte channel (22) for an electrolyte buffer, a supply (23) and opposite thereto a drain channel (24) for a sample, wherein said supply and drain channels each are inclined to said electrolyte channel, and which supply and drain channels intersect said electrolyte channel at supply (25) and drain ports (26), respectively, such that a geometrically defined sample volume (27) is defined by a section of said electrolyte channel located between said supply port and drain port, which sampling device further comprises means for electrokinetically injecting a sample in said geometrically defined sample volume, characterized in that said supply (25) and drain ports (26) are spaced apart from each other longitudinally along the electrolyte channel and form said sample-volume (27). The sampling device is used for electrokinetic sample introduction and capillary electrophoretic separation.