Hamilton STAR Dispensing Inaccuracies

General
1

Hi All,

I am a new user to both Hamilton Systems (Have used Opentrons a lot in the past) and pyLabRobot. For context I am also more of a molecular biologist then automation engineer, but have been tasked with protocol development for our STAR.

I wrote a normalization protocol that theoretically should variable volume repeat dispense diluent into an empty PCR plate then add the correct amount of sample into each plate. I was running water tests and was seeing variable volume levels at the end of the run. After further testing, I figured out that the first part (repeat dispensing diluent) was adding too much water to each well. When I fixed the concentrations to all be the same, it should have been adding 36uL but there was ~39-40 uL in each well.

I was not using a default hamilton liquid class, but I listed the settings I was using below:
flow rate: 100
aspiration settling time: 0.3
dispense settling time: 1
aspiration height: Using LLD
dispense height: fixed height of 1mm

Does anyone have any insight on if this is a liquid class issue or a hardware issue? The system was purchased used, but validated by a third party distributer. I am happy to share more details or the protocol itself if that would be helpful. Thank you all in advance!

2

One way to know if the instrument is in spec is to run the FVK (field verification kit). Hamilton uses scales to verify with a special liquid that your instrument is in spec.

I have no idea what those parameters you are using but typically I start with the default water then tune it gravimetrically with a scale. Elevation and humidity play a large role and liquid classes need to be tuned. Once tuned we fined in the same environment they transfer pretty dang well instrument to instrument.

1 Like
3

Thank you that makes sense. After more digging I think the volume correction curve as causing me my issues. When I changed it from the default from the liquid class to a flat curve all my measurements were coming in more accurately. Some fine tuning is definitely still needed, but it is performing much better. I don’t currently have any scales that can connect with the hamilton, but I will look into it.

Thanks again for the insight!