James Netterwald, PhD, is a freelance science and medical writer based in New Jersey. His writing serves every life science industry.
For anyone who has performed biochemical or molecular biological techniques at any point during the past 40 years, the one tool that has been essential to enduring success is the single-channel pipettor. Although this tool has served us well, it has been cumbersome at times, especially when the user needed to accurately and reproducibly transfer equal amounts of liquid to more than one well of a multiwell plate. The need for reproducible liquid transfer necessitated the development and use of the multichannel pipettor. Since their arrival, multichannel pipettors have dramatically increased the speed, accuracy and reproducibility of manual, high-throughput applications in the life-science, pharmaceutical and clinical arenas.
For those interested in purchasing their first multichannnel pipettor, there are two main features that supersede all others: speed and accuracy. In other words, how quickly do you want your multichannel pipettor to draw up liquids, dispense liquids and eject tips? Also, how accurately (and reproducibly) do you want liquid transfer to occur?
Which features contribute to the pipettor’s accuracy?
If you want a highly accurate multichannel pipettor, consider purchasing one with a motorized piston. This special feature, which is not found in many models, can improve accuracy to 1% or better, while concomitantly improving inter-well reproducibility to 0.1%.
For a multichannel pipettor, the accuracy of liquid transfer also is affected by the range of volumes capable of being ejected from a tip. The volume range can reach a minimum of 0.5 µl in some models; others can load a minimum of 3 µl. In terms of maximum volume, some multichannel pipettors are capable of dispensing as much as 1,200 µl. The range of volumes ultimately depends on the size of the pipette tip you are using and the capacity of your pipettor.
In terms of the number of channels, multichannel pipettors essentially come in two flavors: the eight-channel variety and the 12-channel variety. As a consideration, the number of channels you need depends on your experimental design. For example, if your design calls for the use of a 96-well plate (12 wells by 8 wells), then you could either use an eight-channel or a 12-channel pipettor. However, if your design calls for a 384-well plate (24 wells by 16 wells), then it is more efficient to use a 12-channel pipettor, which, when filling the whole plate with a single liquid, will require 16 passes to fill the entire plate.
The supreme accuracy of the multichannel pipettor vs. the single-channel pipettor is another consideration, as this feature makes the former easier to use. In other words, the accuracy of the multichannel pipettor flattens its learning curve for use, allowing experienced and non-experienced users to become equally proficient within a short period of time.
Which features increase the speed of the pipettor?
Something to consider is whether the dispensing and ejection of liquids are automated functions or manually controlled by the user. Often, electronic pipettors are faster because these processes are automated, and they also have an electronic tip ejector. Both features increase speed.
Another consideration is how the ergonomic design of the multichannel pipettor can speed up liquid-handling processes in your laboratory. Weight is one contributor to the ergonomic design of a pipettor. Multichannel pipettors are typically lightweight, as light as 100 grams, which leads to fewer hand injuries from repetitive use of manual multichannel pipettors. For this reason, manufacturers have been following customer demands by designing pipettors that are increasingly lighter in weight.
What are some other considerations?
Some multichannel pipettors have antimicrobial surface treatments that prevent them from contaminating your samples with bacteria and other microbes. These are well suited to cell-culture work and clinical use, in which sterility is crucial. Finally, multichannel pipettors often have flexible tip heads that enable users to increase or decrease spacing between channels. This is helpful when working with different sizes of plates.
Summary
Multichannel pipettors have made repetitive pipetting easier for high-throughput applications and have reduced the number of work-related hand injuries that are characteristic of manual pipettors.