Pipetmethode

Pipetmethode refers to the set of procedures used to measure and transfer small volumes of liquid with a pipette in laboratory work. The method emphasizes accuracy, precision, and repeatability and is central to experiments, sample preparation, and analytical protocols. Two main approaches are used: air-displacement pipetting, which relies on an air cushion to move liquid, and positive-displacement pipetting, in which a disposable plunger moves liquid directly.

Equipment and terminology include micropipettes with defined volume ranges, disposable pipette tips made of compatible plastics, and accessories such as tip ejectors and racks. Calibration and routine maintenance are essential to ensure accuracy and are governed by international standards, notably ISO 8655 and related laboratory practices. Temperature, viscosity, and surface tension influence measurement and should be considered.

Basic technique involves a series of controlled steps. Pre-wet the tip with a small amount of the target liquid to improve accuracy. Set the desired volume, attach the tip, and immerse it to the recommended depth. Depress the plunger to the first stop to aspirate, pause briefly to reduce flow disturbance, then release to the second stop to dispense. Keep the pipette vertical during aspiration and dispense, and eject the used tip after use. For serial dilutions and multi-volume transfers, consistent technique and thorough mixing are important.

Common issues include bubbles, incorrect immersion depth, angling the pipette, temperature differences between liquid and instrument, and tip incompatibility. Regular calibration, proper storage, and routine cleanliness help maintain performance.

Applications span molecular biology, analytical chemistry, clinical laboratories, and educational settings. Automated liquid handlers provide throughput gains but rely on the same pipetting principles.

See also: micropipette, dilution, calibration.