Pipettes

Pipettes are handheld instruments commonly used in academic, biotech, pharmaceutical and other labs to transfer precise amounts of liquid from one container to another.

Pipettes range from very basic graduated glass tubes to sophisticated precision instruments that, along with pipette tips are capable of aspirating and dispensing liquid in increments as small as a fraction of a microliter.

The most common pipette used in life science labs around the world is the single-channel air displacement pipette. Pipettes are available in both manual and electronic models and are available as single channel, multichannel, and multichannel adjustable spacer pipettes.

There are two types of pipettes: Positive displacement and air pipettes. Positive displacement pipettes are commonly used for samples of high viscosity (e.g. glycerol) or high vapor pressure (e.g. volatiles like alcohol), while air-displacement pipettes can be used for a majority of laboratory applications.

Modern pipettes work with a piston-stroke principle – liquid is measured using the piston-cylinder system in the handle of the pipette. When the piston is depressed and then slowly released, the movement of the piston creates a vacuum in the pipette tip and thus draws liquid up inside the tip; which is called aspiration.

Since the piston in a pipette is a long way from the liquid sample, the air cushion between the piston and liquid can have a number of effects on the accuracy of this process, depending on the liquid type.

Pressing down on the plunger that has a tip full of liquid expels the liquid out from the tip; this is called dispensing.

Positive displacement pipettes work on a similar principle, however te tip of the positive displacement system contains its own piston and hence there is a minimal air cushion between the piston (that is part of the tip) and the liquid surface.

Pipetting accuracy is the ability of a pipette to deliver the volume specified on the volume setting. In other words, the trueness of a measurement to the true value depends on the interplay of the elements in the system.

Pipetting precision is the ability of a pipette to consistently deliver same-sized volumes of liquid over multiple aliquots. A pipette can be precise with regard to dispensing the same volume time after time, yet inaccurate because it fails to dispense the correct volume. An accurate and precise pipette dispenses volumes at the intended volume with each dispense.

The pipette, the pipette tip, and the person operating the pipette form a 3-part system. The pipette operator, the person using the pipette to conduct research, has a high degree of influence on the accuracy of results. As such, it is important that operators are trained to use a pipette. There are some powerful, yet simple techniques that can greatly improve pipetting accuracy. The Rainin Pipetting Technique poster offers a good summary.
Additionally, Rainin offers the Good Pipetting Practice online seminar to assist in learning the proper way to pipette.

Pipetting is a repetitive activity that can involve a high level of force when loading and ejecting pipette tips. As with any repetitive activity, over time, the risk of developing musculoskeletal injury, such as carpal tunnel syndrome, tendinitis and other repetitive strain injuries (RSIs) has a large potential to increase.

While good posture and stretching can provide relief, the key to preventing injury is reducing pipetting forces. The Rainin LiteTouch System (LTS), which involves both the pipette and the pipette tip, was invented by Rainin with ergonomic pipetting as a core emphasis and helps reduce tip ejection force up to 85%.

Read more about pipetting ergonomics.

Pipette calibration refers to testing a pipette's precision and accuracy and resetting it to the manufacturer's specifications.

A common method of pipette calibration is the gravimetric method, which involves pipetting distilled water onto an analytical balance and weighing it to assess the accuracy of the measurement.

We offer pipette calibration plans to meet the specific needs of regulated laboratories. We calibrate all major pipette brands to each manufacturer's specifications. Options for pipette calibration plans include preventive maintenance – including the replacement of the dry seal and O-ring/shaft.

Rainin offers a wide range of manual or electronic single channel, multichannel, or high throughput pipetting instruments as well as calibration services to ensure your results remain accurate. In addition, the related lab equipment helps you to optimize the performance of your pipette.