Abstract
A micro-injector was developed for electrophoretic analysis of a microlitre amount of samples, enabling injection of the sample directly from a Hamilton syringe. The outlet of the syringe needle is placed directly opposite the inlet of the separation capillary at a distance of the order of hundreds of μm in the injection space.
During the injection, the background electrolyte is forced out by air from this space and a microliter drop of the sample is forced out of the syringe by a micro-pump so that it is caught at the entrance to the capillary. From the drop the sample is hydrodynamically injected into the capillary or simply by spontaneous drawing in by capillary forces.
The injection space is then filled with background electrolyte, which washes away excess sample and separation is commenced.