A method of avoiding decreased-size first drops when aspirating from immersed rest conditions

摘要

A method for avoiding a reduction in volume of the first drop dispensed by a pump from a dispensing tip stored immersed within the liquid to be dispensed. The method comprises the steps of: a) while the tip is still immersed in the liquid, dispensing enough air from the tip into the liquid to create an air bubble which, when the tip is withdrawn from the liquid, will break apart, b) withdrawing the tip from the reservoir to cause the bubble to separate therefrom, optionally producing a skin of liquid across the tip orifice, c) aspirating the optional skin and a small amount of air into the tip at least two times, d) ejecting more volume of air than was aspirated in step c), leaving at most only traces of liquid in the tip, e) adjusting the pump so as to position it at about the center point of its dispense/aspirate cycle, f) immersing the tip back into the reservoir of liquid, g) aspirating an amount of the liquid from the reservoir into the tip, and dispensing the aspirated amount back into the reservoir, the amount being enough to substantially clean out the traces of liquid, and h) thereafter, aspirating the preselected amount of liquid for subsequent dispensing.