Bubbles/drips on tips when doing an over-aspirate - can this be prevented using liquid class?

Hello all, I have a liquid class question. I created a method that aspirates 500uL of DMSO from a glass vial to a barcoded tube. The reason I went with set volumes is that the vol in the glass vial can vary from 100-500uL, so the lazy way to deal with this is just use the max vol for every transfer. I’ve been testing the method, and I noticed that on some transfers there are bubbles and drips at the end of the dispense. I’m assuming that this is due to overaspiration (aspirating 500uL when there’s only 200uL of liquid = turbulence and bubbles in the tip). Does anyone have any advice for addressing this on a liquid class level? If I can’t get this figured out I might have to adjust my method to do variable volumes for each transfer, which is doable. Thank you!

Hi @lgoeser

The bubbles and dripping observed after dispense are almost certainly due to over aspiration of air for lower volume aliquots.

If the volume variability range was lower than 400uL you could increase the air transport volume for dispense but this will be too much to solve via liquid class parameters.

Are the volumes known prior to loading? If so I would use a worklist and aspirate variable volumes. If not, I would determine an estimated volume prior to aspiration by detecting liquid level relative to the bottom of the container and calculate volume based on container geometry. See a couple of relevant threads linked below:

Thread 1

Thread 2