Positive displacement pipette having an improved ejection function

A pipetting method using a positive displacement sampling pipette including

• a control rod having a bottom end which controls a displacement of a device for gripping a top end of a piston belonging to a capillary-piston assembly adapted to cooperate with said pipette, the pipette including an ejection rod for ejecting said capillary-piston assembly, said ejection rod being movably disposed within said control rod such that a bottom end of the ejection rod exerts an ejection strain on the top end of said piston accommodated in said gripping device during a relative displacement between the ejection rod and the control rod, and the gripping device having a form of a clip having at least two radially outwardly-biased jaws biased into a clamped position by elastic return means,
• the pipetting method comprising the following successive steps:
• (a) fitting a capillary of the capillary-piston assembly onto a tip of the pipette, and introducing the top end of the piston of the assembly into the clip during the displacement of said control rod into a low position, said introducing being performed by moving apart the at least two radially outwardly biased jaws by bearing the top end of the piston, said moving apart being allowed by deforming said elastic return means associated with said at least two radially outwardly biased jaws;
• (b) sampling and dispensing a sample by actuating said control rod;
• and
• (c) ejecting the capillary-piston assembly by actuating said ejection rod.