At the end of our September 2016 Webinar on “Troubleshooting Liquid Handler Methods,” a viewer asked the following assay validation question:
There are really two parts to this question:
We’ve addressed these issues in two Application Notes, summarized here (and downloadable from the Artel website; links provided below in the Additional Resources list).
It’s not uncommon for a lab to want to verify volume transfer into a specific type of plate. Because plate type can affect volume transfer, labs that need a high degree of confidence in their volume verification will typically dispense into the same plate type used in a live assay.
In the field test application of this process [using a 384-channel Biomek FX], the users of the Biomek insisted that the target volume be dispensed into the v-bottom plate (assay plate). They did not want to dispense the target volume directly into the MVS-compatible plate because “…it was not the same geometry and the automated methods could act differently…the tip depth and tip touches might not perform the same in the different plate and then I won’t know if the source of error is the plate or my method or both.”1
What, then, can an automated liquid handler user do if the receiving plate is not compatible with the MVS? In this situation, you need to add a second transfer step to move the sample from the original receiving plate into an MVS-compatible plate. In order to optimize the efficiency of this extra transfer, we recommend a series of Diluent additions and transfers as summarized in Figure 1.
The full protocol and proof-of-concept data for this method can be found in the application note, “Volume Verification Using Any Microtiter Plate or Small Volume Container Such as a Tube or Vial.”
While generally useful, there are some considerations and limitations to bear in mind, which are also discussed in the application note. One that I’d specifically like to mention here is what to do if your transfer volume is too large to accommodate enough Diluent additions and transfers. In this situation, we recommend that you first transfer the target volume to the MVS-compatible plate type that holds the largest working volume, and then transfer the remaining target volume with Diluent steps. You can also check how much residual volume is left in a plate after aspiration using the MVS, to be sure that you’ve maximized transfer efficiency.
You can use a similar Diluent-based transfer method to measure the amount of residual sample left in a non-MVS plate, which is summarized in Figure 2. The full details of the protocols and the simpler method that can be used for MVS-compatible plates are covered in the application note, “Measuring Residual Volumes Remaining in a Plate After Sample Aspiration.”
If your assay calls for transfer into specialized plates, you can use the MVS to verify volume transfer with high confidence. The benefits of this approach – reliable, reproducible assay data – will be worth the effort.
1. Keith J. Albert. Volume Verification Using Any Microtiter Plate or Small Volume Container Such as a Tube or Vial. Application Note 12A5553A (2007).
Keith is an expert in liquid handling performance management, providing customized services across a wide range of platforms, applications, liquid volumes, and liquid classes. As Senior Applications Specialist, Keith combines his extensive knowledge and experience with rigorous science in his work in liquid handling system performance research, customer education, and assay/method validation.