Pipettes and Pipette Tips

Pipettes and Micropipettes

The first pipettes were simple graduated tubes designed to take up fluid by suction and dispense it by gravity flow. Originally made of glass, pipettes may now be glass for reusability or solvent resistance, or for high-accuracy volumetric pipettes, but are more typically single-use, presterilized pipettes designed for single use.

Non-graduated pipettes include Pasteur pipettes, small-volume glass tubes with a fine tip and an attached rubber suction bulb, and low-accuracy, soft plastic transfer pipettes with an integrated suction bulb, often used for sample collection or dispensing small amounts of fluid in applications where volumetric accuracy is not critical, for example, an eye dropper.

Pipette outflow in an open-ended pipette can be controlled by slowly releasing the partial vacuum in the pipette with a finger closing the top of the tube, or by attaching a suction device with a release valve to the top of the pipette, known as a pipette aid or propipetter.

The past use of mouth pipetting in a laboratory with potentially toxic or biohazardous liquids is an unsafe practice, since replaced by using an electronic pipette aid, or pipette controller, such as our Professional Pipette Controller, which provides not only safety but precision and ease of use, a benefit for those with a large pipetting workload.

Open-tube pipettes are typically used to deliver volumes of 1-50 ml. The first micropipettes, designed to accurately dispense microliter volumes, were invented in the late 1950s. They consist of two parts, the micropipette, sometimes called a micropipettor, and disposable single-use plastic pipette tips that fit on the open end of the micropipette. Rather than an open top, the micropipette has an internal piston that uses air displacement to both draw liquid up into the pipette tip and expel the liquid to dispense it.

Air-displacement micropipettes can be fixed-volume, as in our educational micropipettes, but most laboratories use adjustable micropipettes to deliver liquid volumes from 0.1 µl to 1,000 µl (1 ml), such as our Professional Adjustable-Volume Digital Micropipettes, with a thumb-activated liquid piston and tip ejector and a volume adjustment dial.

These are also referred to as single-channel pipettes, as opposed to multi-channel pipettes, such as our 8-channel Professional Multichannel Micropipette, which are designed to facilitate high-throughput screening work in 96-well or 384-well plate formats.

Micropipette Calibration

Most regular micropipette users should have their pipets calibrated at six-month intervals. This calibration can be done by the manufacturer or a licensed vendor. However, for labs with an analytical balance available, a quick check of your micropipettes can be done by pipetting a specific volume of distilled water directly onto the balance pan, or onto a tared weigh boat, and checking that the weight is correct; for example, 1 ml should weigh 1 g. Of course, the balance must also be periodically calibrated. Pipette users in regulated industries such as clinical or pharmaceutical labs may be required to calibrate their pipettes more often and keep traceable calibration records, and such a casual calibration check would not be an acceptable substitute.