INJECTION OF ULTRASMALL SAMPLES AND SINGLE MOLECULES INTO TAPERED CAPILLARIES

A novel injection scheme is described in which ultrasmall samples in t he attoliter (10(-18) L) and low femtoliter (10(-15) L) range, or even single molecules, are controllably introduced into a tapered capillar y so that electrophoretic separation can be carried out. To match the dimensions of the capillary inlet with that of the sample, capillary t ips are tapered to an inside diameter ranging from hundreds of nanomet ers to a few micrometers. To inject an ultrasmall sample, optical trap ping is used to immobilize and manipulate the sample in order to place it inside or next to the capillary inlet. A small controlled suction results in the loading of the sample into the capillary.