Pipettes are a common laboratory tool used across chemistry and biology to measure, dispense and transport liquid. 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. They all work using a similar principle by creating a partial vacuum above the liquid-holding chamber and selectively releasing this vacuum to draw up and dispense liquid.
ProSciTech supply various brands and styles, see the full collection of pipettes, pipette fillers/controllers, pipette tips and pipette accessories or see below for more details on how to select the pipette that's right for your application.
Air Displacement Pipettes
These are adjustable pipettes that delivers measured volume of liquid, generally between about 0.1µl to 1,000µl (1ml). The manual movement of a piston using the thumb creates a vacuum to both draw up and dispense the liquid. These pipettes require disposable tips that come in contact with the fluid being pipetted. They are capable of being very precise and accurate but are subject to inaccuracies caused by the changing environment, particularly temperature and user technique.
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Electronic Pipettes
Electronic pipettes commonly replace the mechanical version to improve the ergonomics of pipetting by reducing the necessary force and possible development of musculoskeletal disorders due to repetitive pipetting. The manual movement of the piston is replaced by a small electric motor powered by a battery. Whereas manual pipettes need a movement of the thumb (up to 3 cm), electronic pipettes have a main button. The programming of the pipette is generally done by a control wheel and some further buttons. All settings are displayed on a small display. These pipettes require disposable tips that come in contact with the fluid being pipetted.
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Positive Displacement Pipettes
These are less common but similar to air displacement pipettes and are used to avoid contamination and for volatile or viscous substances at small volumes, such as DNA. The major difference is that the disposable tip is a more complex with a microsyringe (plastic), composed of a capillary and a piston (movable inner part) which directly displaces the liquid.
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Volumetric Pipettes
Volumetric pipettes or bulb pipettes allow the user to measure a volume of solution extremely precisely (precision of four significant figures). These pipettes have a large bulb with a long narrow portion above with a single graduation mark as it is calibrated for a single volume (like a volumetric flask). Typical volumes are 20, 50, and 100ml. Volumetric pipettes are commonly used to make laboratory solutions from a base stock as well as prepare solutions for titration. They require a vacuum source called a filler or controller to be used to fill and dispense the pipetting liquid.
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Graduated Pipettes
Graduated pipettes are a type of macropipette consisting of a long tube with a series of graduations, much like a graduated cylinder or burette, to indicate different calibrated volumes. They require a source of vacuum attached to fill and dispense the pipetting liquid. There are various pipette bulbs, manual and automatic fillers and controllers available.
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Pasteur and Transfer Pipettes
Pasteur and transfer pipettes are used to transfer small amounts of liquids and are not graduated or calibrated for any particular volume. Pasteur pipettes (also called teat pipettes, droppers, eye droppers and chemical droppers) are plastic or glass pipettes where the pipette body is separate to the bulb. Transfer pipettes (also known as Beral pipettes) are made from a single piece of plastic where the bulb also serves as a chamber to hold liquid.
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Cleaning and Maintenance
Micropipettes and pipettors should be carefully maintained and calibrated, and users trained to exercise correct and consistent technique. It is recommended that you check the calibration at least every six months for regularly used pipettes. Companies in the drug or food industries are required to calibrate their pipettes at shorter intervals and should follow the set guidelines. Those in forensics and research where a great deal of testing is commonplace will perform monthly calibrations.
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