Glycerol LC Help

Hi all!

I am struggling with liquid class optimization of an air Fluent when dispensing 50% glycerol solution. I saw there was an earlier post about this reagent, but I’m less concerned with precision, and more concerned with how the heck to get droplets off my tips for viscous reagents.

Normally I will just dispense at z-max with tracking if I don’t want droplets. Unfortunately, I need to dispense at the top of the well for this process to prevent cross-contamination (I’m hoping to avoid using new tips for each plate). Adding a tip touch is risky.

Has anyone worked through this and found particular settings helpful? The aspiration parameters seem okay, for dispense I’ve played around with dispense speed, increased delays, and included about volume sized leading air gap. I think the leading air gap helped the most(?), but I’m still seeing droplets. The droplets fall from the tips while moving across the deck, and in some scripts have caused glycerol to get up in the EVA. I tried comparing water free single to DMSO free single and MM free single to get an idea, but the standard DMSO and MM LCs only have values for the FCA.

Thank you!

What arm, tip type, volume?
Viscous liquid needs to be aspirated and dispensed slow due to viscous liquid properties and is typically done with a contact dispense. When you try a free dispense out of the air and the liquid leaves the tip slow (since its viscous), then it doesn’t break off nicely from the tip (unlike when water based liquids are dispensed fast). Hence the droplets. I would try to take a ‘Trailing airgap after dispense’, if you haven’t already, to address your point about prevent droplets falling from the tip when the arm moves. It’s a checkbox in the liquid class at Dispense - Easy Control

For viscous liquids on the Fluent the company Tecan recommends not to do free dispense. The other recommendations are the following:

  • Always aspirate slow
  • Always dispense slow
    - contact dry dispense
    - contact wet dispense
    - wall dispense

With this try the following

  • Slow retract / slow ‘swap speed’
  • long delay (500 - 1000 ms)
  • make sure there is a good Trailing Air Gap (TAG), but keep total LAG & TAG < 30uL.