James Netterwald, PhD, is a freelance science and medical writer based in New Jersey. His writing serves every life science industry.
The automated liquid handler—built to precisely move liquids from one vessel to another in applications ranging from nucleic-acid purification and DNA sequencing to high-throughput screening of pharmaceutical compounds—has become a powerful and popular tool in labs throughout the life-science industry. Although useful and sure to expedite almost any application, an automated liquid handler can be quite costly, so consider the following before purchasing one.
Dispenser type
There are three main choices for dispensers. First, there are peristaltic pumps, which can precisely dispense nanoliter volumes of liquid with very little priming necessary; these are self-priming. Second are microprocessor-controlled syringes, which, like peristaltic pumps, can dispense nanoliter volumes but with much more rapid output and higher precision. In general, syringe-operated dispensers require more priming than peristaltic pumps, but the amount of priming depends on the system. Finally, there are hybrid detection systems that combine both technologies in one unit; in addition to liquid handling, such systems perform washing functions.
Sample volume and flow rate
After you decide on a type of dispenser, you should consider the volume range you require in a liquid handler. As with other considerations discussed in this article, the appropriate volume range depends on your application. For example, applications performed in smaller culture vessels or assay plates (e.g., 384 wells) require a lower liquid-volume range than those performed in larger vessels or plates (e.g., six or 24 wells).
Another application-specific consideration is the automated liquid handler’s flow-rate spectrum. Higher flow rates may be necessary for temporally sensitive enzymatic or cell-based assays. Slower flow rates may be necessary for chromatographic assays.
Special considerations for PCR
If you plan to use your automated liquid handler to perform PCR-based assays, it is important to determine if the instrument contains a thermal-regulatory module that ensures temperature regulation in the heating blocks. Also, for PCR-based assays, make sure your automated liquid-handling workstation can protect your samples against cross contamination from previously amplified DNA templates.
Special considerations for immunoassays
If you plan to conduct immunoassays, make sure your automated liquid handler can accommodate magnetic or plastic bead-based assays. Specifically, ensure that your workstation is equipped with an appropriate magnet to attract the magnetic beads used in your assay.
Throughput
Finally, what throughput do you require for assays that will be performed using your liquid handler? A high-throughput instrument is definitely necessary for most pharmaceutical applications, including high-throughput screening (HTS), GPCR assays, pharmacokinetics, etc., as well as for DNA-sequencing applications. Clinical labs should consider purchasing a high-throughput liquid handler to accommodate the typically high volume of samples they process. Low- or medium-throughput instruments may be more appropriate for some chromatographic applications, such as certain protein purification steps.
Automated liquid handlers can be useful in many applications. Finding the right one for your research is simply a matter of considering these key criteria and matching them to your needs.