micropipet

A micropipet, or micropipette, is a laboratory instrument used to measure and transfer very small volumes of liquid with high precision. They are essential for tasks that require accurate dosing of reagents, samples, or standards, typically in the microliter range. Commonly used models have volume ranges such as P20, P200, and P1000, corresponding to different maximum capacities, and they may be air-displacement or positive-displacement types. Multichannel versions exist for rapid handling of multiple samples.

Most micropipets share a similar design: a precision plunger, a volume-adjustment dial, a shaft that accepts a disposable tip, and a tip-ejector. The tip is attached to a disposable plastic cartridge, which prevents cross-contamination between samples. Air-displacement pipettes are the standard for many biological applications; positive-displacement pipettes are used for viscous or volatile liquids where air compression would introduce larger errors. Manual and electronic variants are available, with electronic models offering programmable steps and reduced hand fatigue.

Operation involves setting the desired volume, attaching a sterile tip, pre-wetting the tip by aspirating and dispensing a small amount, and then aspirating the target volume slowly before dispensing with a smooth, steady press of the plunger. Techniques such as reverse pipetting or two-step aspiration may be used for viscous liquids or foaming samples to improve accuracy.

Calibration and maintenance are essential for accuracy. Pipettes should be calibrated regularly according to standards such as ISO 8655, typically using gravimetric methods. Maintenance includes tip compatibility checks, clean storage, and avoidance of exposure to extreme temperatures or solvents. Common issues include air leaks, bent shafts, or improper tip seating, which can affect precision and accuracy.

Applications span molecular biology, biochemistry, clinical diagnostics, and environmental testing, where precise liquid handling is fundamental. Proper technique and routine verification help minimize systematic or random errors in experimental results.