Pipette

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A pipette (also called a pipet, pipettor or chemical dropper) is a laboratory instrument used to transport a measured volume of liquid.

Contents

Use and variations

Pipettes are commonly used in molecular biology as well as medical tests. Pipettes come in several designs for various purposes with differing levels of accuracy and precision, from single piece glass pipettes to more complex adjustable or electronic pipettes. Many pipette types work by creating a partial vacuum above the liquid-holding chamber and selectively releasing this vacuum to draw up and dispense.

Pipettes that dispense between 1 and 1000 μl are termed micropipettes, while macropipettes dispense a greater volume of liquid. Two types of micropipettes are generally used: air-displacement pipettes and positive-displacement pipettes. In particular, piston-driven air-displacement pipettes are micropipettes which dispense an adjustable volume of liquid from a disposable tip. The pipette body contains a plunger, which provides the suction to pull liquid into the tip when the piston is compressed and released. The maximum displacement of the plunger is set by a dial on the pipette body, allowing the delivery volume to be changed. Larger capacity tubular pipettes, such as volumetric or graduated pipettes are used by temporarily attaching a pipetting aid. Pipetting syringes typically handle volumes in the 0.5mL to 25mL range, for aliquot transfer and incremental dispensing in titrations, with a positive displacement method of operation. No disposable tips or pipetting aids are needed with the pipetting syringe.

Piston-driven air displacement pipettes

These pipettes operate by piston-driven air displacement. A vacuum is generated by the vertical travel of a metal or ceramic piston within an airtight sleeve. As the piston moves upward, driven by the depression of the plunger, a vacuum is created in the space left vacant by the piston. Air from the tip rises to fill the space left vacant, and the tip air is then replaced by the liquid, which is drawn up into the tip and thus available for transport and dispensing elsewhere. These pipettes are capable of being very precise and accurate, however, being air displacement, are subject to inaccuracies caused by the changing environment, particularly temperature and user technique. For these reasons this equipment must be carefully maintained and calibrated, and users must be trained to exercise correct and consistent technique. These micropipette were invented and patented 1960 by Dr. Hanns Schmitz (Marburg/ Germany). Afterwards, the co-founder of the biotechnology company Eppendorf, Dr. Heinrich Netheler, inherited the rights and initiated the global and general use of micropipettes in labs. In 1972, the adjustable micropipette was invented at the University of Wisconsin-Madison by several people , primarily inventor Warren Gilson and Henry Lardy, hence one of the bigger producers is the original company called Gilson Inc., as a result they are colloquially referred to as Gilsons [1] [2].

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