Pipette is one of the most common tools used in biological, clinical, and analytical laboratories where liquids need to be precisely measured and transferred when performing dilutions, assays or blood tests. They are available as:
① single-channel or multi-channel
② fixed or adjustable volume
③ manual or electronic
What are Single-Channel Pipettes?
The single-channel pipette allows users to transfer a single aliquot at a time. These tend to be used in laboratories with a low throughput of samples, which can often be those involved in research and development.
The single-channel pipette has one single head to aspirate or dispense very accurate levels of liquid through a disposable tip. They can be used for multiple applications within laboratories which only have a small throughput. This is often laboratories which perform research related to analytical chemistry, cell culture, genetics or immunology.
What are Multi-Channel Pipettes?
Multi-channel pipettes function in the same way as single-channel pipettes, but they utilise multiple tips for measuring and dispensing equal amounts of liquid at once. Common setups are 8 or 12 channels but 4, 6, 16 and 48 channel sets are also available. 96 channel benchtop versions can also be purchased.
Using a multi-channel pipette, it’s easy to quickly fill a 96-, 384-, or 1,536-well microtiter plate, which may contain samples for applications such as DNA amplification, ELISA (diagnostic test), kinetic studies and molecular screening.
Single-Channel vs. Multi-Channel Pipettes
Efficiency
The single-channel pipette is ideal when doing experimental work. This is because it mainly just involves using individual tubes, or a single cross-match to perform in blood transfusion.
However, this quickly becomes an inefficient tool when throughput is increased. When there are multiple samples/reagents to transfer, or larger assays are being run in 96 well microtitre plates, there is a much more efficient way to transfer liquids then using a single-channel pipette. By using a multi-channel pipette instead, the number of pipetting steps is dramatically reduced.
The table below demonstrates the number of pipetting steps required for a single-channel, 8 and 12 channel setups.
Number of pipetting steps required (6 reagents x 96 Well Microtitre Plate)
Single-channel Pipette: 576
8-Channel Pipette: 72
12-Channel Pipette: 48
The Volume of Pipetting
One key difference between the single and multi-channel pipettes is the volume per well that can be transferred at one time. Although it depends on the model being used, generally you cannot transfer as much volume per head on a multi-channel pipette.
The volume a single-channel pipette can transfer ranges between 0.1ul and 10,000ul, where the range of a multi-channel pipette lies between 0.2 and 1200ul.
Sample Loading
Historically, multi-channel pipettes have been unwieldy and difficult to use. This has caused inconsistent sample loading, along with difficulties loading tips. There are newer models available now however, which are more user-friendly and go some way to remedy these issues. It is also worth noting that although liquid loading may be a little more inaccurate with a multi-channel pipette, they are more likely to be more accurate overall than single-channel due to the inaccuracies which occur from user error as a result of fatigue (see next paragraph).
Reducing Human Error
The likelihood of human error is drastically reduced as the number of pipetting steps decreases. Variability from fatigue and boredom are removed, resulting in data and results which are reliable and reproducible.
Calibration
To ensure the accuracy and precision of liquid handling devices, regular calibration is required. Standard ISO8655 states that each channel must be tested and reported. The more channels a pipette has, the longer it takes to calibrate which can be time-consuming.
According to pipettecalibration.net a standard 2.2 calibration on a 12-channel pipette requires 48 pipetting cycles and gravimetric weighings (2 volumes x 2 repetitions x 12 channels). Depending on the speed of the operator, this can take over 1.5 hours per pipette. Laboratories in the United Kingdom requiring UKAS calibration would need to perform a total of 360 gravimetric weighings (3 volumes x 10 repetitions x 12 channels). Performing this number of tests manually becomes impractical and may outweigh the time savings achieved by using a multi-channel pipette in some labs.
However, to overcome these problems pipette calibration services are available from several companies. Examples of these are Gilson Labs, ThermoFisher and the Pipette Lab.
Repair
It’s not something that many think about when buying a new pipette, but the manifold of some multi-channel pipettes is not repairable. This means if 1 channel is damaged, the entire manifold may have to be replaced. However, some manufacturers sell replacements for individual channels, so be sure to check repairability with the manufacturer when purchasing a multi-channel pipette.
Summary – Single vs Multi-Channel Pipettes
The multi-channel pipette is a valuable tool for every laboratory who have anything more than a very small throughput of samples. In almost every scenario the maximum volume of liquid required for transfer is within the capacity of each tip on a multi-channel pipette, and there are very few drawbacks associated with this. Any minor increase in complexity in using a multi-channel pipette is greatly outweighed by the net decrease in workload, enabled by a drastically reduced number of pipetting steps. All this means improved user comfort, and decreased user error.
Post time: Dec-16-2022