A microfluidic injector for capillary electrophoresis, comprising: an electrophoresis separation device ; a substrate having an injection channel having a first end connected to a buffer supply and a second end connected to the electrophoresis separation device , a sample inlet channel connected to the injection channel , a buffer inlet channel connected to the injection channel , and a first waste channel connected to the injection channel ; a selectively controllable first valve disposed in the sample inlet channel ; a selectively controllable second valve disposed in the buffer inlet channel ; a selectively controllable third valve disposed in the first waste channel ; a selectively controllable fourth valve disposed in the injection channel and positioned such that closing the fourth valve seals the buffer supply from the sample inlet channel , the buffer inlet channel and the first waste channel ; a selectively controllable fifth valve disposed in the injection channel and positioned such that closing the fifth valve seals the electrophoresis separation device from the sample inlet channel , the buffer inlet channel and the first waste channel , and wherein a first sample chamber having a first defined volume is formed in the injection channel by and between the fourth valve and the fifth valve ; a power supply configured to apply a capillary electrophoresis separation voltage between the buffer supply and an output of the electrophoresis separation device and across the injection channel so as to drive the sample located in the injection channel between the fourth valve and the fifth valve through the electrophoresis separation device ; and wherein the electrophoresis separation device is selected from the group consisting of: a silica capillary; a capillary channel formed in the substrate; and a capillary channel disposed on the substrate . an electrophoresis separation device ; a substrate having an injection channel having a first end connected to a buffer supply and a second end connected to the electrophoresis separation device , a sample inlet channel connected to the injection channel , a buffer inlet channel connected to the injection channel , and a first waste channel connected to the injection channel ; a selectively controllable first valve disposed in the sample inlet channel ; a selectively controllable second valve disposed in the buffer inlet channel ; a selectively controllable third valve disposed in the first waste channel ; a selectively controllable fourth valve disposed in the injection channel and positioned such that closing the fourth valve seals the buffer supply from the sample inlet channel , the buffer inlet channel and the first waste channel ; a selectively controllable fifth valve disposed in the injection channel and positioned such that closing the fifth valve seals the electrophoresis separation device from the sample inlet channel , the buffer inlet channel and the first waste channel , and wherein a first sample chamber having a first defined volume is formed in the injection channel by and between the fourth valve and the fifth valve ; a power supply configured to apply a capillary electrophoresis separation voltage between the buffer supply and an output of the electrophoresis separation device and across the injection channel so as to drive the sample located in the injection channel between the fourth valve and the fifth valve through the electrophoresis separation device ; and wherein the electrophoresis separation device is selected from the group consisting of: a silica capillary; a capillary channel formed in the substrate; and a capillary channel disposed on the substrate . <EOS>