Principle and simple classification of pipettes

A pipette, also known as a micropipette or a sampling gun, is a precision instrument used in laboratories to quantitatively transfer small amounts of liquid volume. It can be used to measure a single volumeA liquid with a concentration of 0.1 μ L-10mL can achieve precise liquid ratio transfer, and is commonly used in environmental testing, medical laboratories, biotechnology laboratories, food testing laboratories, pharmaceutical research laboratories, etc. It is used for sample collection and transfer in contemporary research processes such as biology, chemistry, and clinical experimentsimportantOne of the tools, mainly used in the preparation stage of samples in medical clinical laboratories.

Working Principle:

In short, the basic principle is to use the extension and contraction motion of a spring to drive the piston to move, thereby achieving the action of suction and discharge. However, the specific working principle of different pipettes is slightly different. Currently, liquid pipettes on the market can be mainly divided into two categories based on their principles: exhaust micro pipettes and positive displacement pipettes.

Exhaust type micropipette:alsoIt is called an air cushion piston pipette, and its working principle is that the piston moves through the extension and contraction of the spring and uses air pressure to achieve the action of suction and discharge. Under the push of the piston, the pipette discharges some air, uses atmospheric pressure to suck in liquid, and then pushes the air to discharge the liquid by the piston. The function of the air cushion is to separate the liquid sample sucked into the plastic suction head from the piston inside the pipette. The air cushion moves through the spring movement of the pipette piston, indirectly driving the suction and discharge of the pipette in the suction head. This type of pipette has high accuracy and precision, and is suitable for routine pipetting operations. However, this air cushioned piston pipette has a section of air remaining in the system during the pipetting process, making it unsuitable for suctioning liquids with high viscosity and some volatile liquids.

Positive displacement pipette:It is an external piston type pipette. Unlike the exhaust type pipette, the piston of the forward displacement pipette is in direct contact with the liquid, and there is no air cushion separating the piston from the liquid. The liquid is directly drawn in and expelled through the movement of the piston. Because the liquid comes into direct contact with the piston without the obstruction of an air cushion, this type of pipette is suitable for the transfer of liquids with high viscosity, high density, bubbly liquids, and volatile liquids.

In addition, in addition to the above two types of pipettes, commonly used pipettes in laboratories include volumetric pipettes, graduated pipettes, and Pasteur pipettes. Strictly speaking, these three types also belong to pipettes, but due to their simple structure, we generally prefer to call them pipettes. The pipettes I generally refer to are highly automated, accurate, and structurally complex exhaust micro pipettes and forward displacement pipettes.

Other categories:

In addition to categorizing based on principles, pipettes can also be classified according to other criteria within the industry as follows:

lAccording to the allowed number of suction heads installed: single channel pipettes and multi-channel pipettes;

lAccording to whether the scale is adjustable: fixed pipette and adjustable pipette;

lAccording to the scale adjustment method: manual pipette and electric pipette;

lAccording to special purposes: fully disinfected pipettes, large capacity pipettes, bottle mouth pipettes, continuous injection pipettes, etc

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