A falling drop for sample injection in capillary zone electrophoresis

The inlet of a capillary is joined to an open stream of buffer formed on an inclined narrow surface, and a constant voltage is applied to the capillary. A drop of sample falls directly to the capillary inlet and then is washed away quickly, Thus, a short sample plug with limited dilution by the buffer stream and limited fronting or tailing is injected in electrokinetic mode. No moving parts are involved, and no adjustment of voltage is necessary in the injection process. The method is simple, reproducible, easy to automate and should prove to be a valuable complement to the present injection techniques for capillary zone electrophoresis.