Simple and Fast Performance Verification for Ultra-Low-Volume Liquid Handlers

Nanoliter Aqueous Fluid Transfers Assessed with Dual-Dye Technology


Poor liquid handling performance can lead to poor assay results. When the volume verification methodology used to assess liquid handler performance is not properly executed, errors will enter into the process and the results could lead to incorrect conclusions regarding instrument performance. This presentation discusses proper techniques and best practices for assessing aqueous liquid transfer accuracy and precision for low-volume liquid handlers. These practices were established using both acoustic droplet ejection (Echo® 555 liquid handler, Labcyte Inc.) and a feedback-controlled, tip-based dispenser (Deerac™ GX reagent dispenser, Labcyte Inc.). Volumetric accuracy and precision were measured using a standardized volume verification platform based on a dual-dye absorbance technology (MVS®, Artel) and compared to fluorescencebased tests. For absorbance testing, manufactured aqueous-based dye solutions were employed for all target volumes and diluents. For fluorescence testing, sodium fluorescein (150 mM) in water was used for target volumes and sodium hydroxide (10 mM) was used as diluent. In both cases, the dye solution was transferred into a 384-well test plate with the Echo (30 – 200 nL) or the Deerac GX system (200 – 800 nL) followed by the addition of buffer. Using the MVS, the measured accuracy and precision for both the Echo and Deerac GX Series were below 5% inaccuracy and 5% CV for the volume transfers indicated. Some of the best practices developed and discussed herein include source plate preparation, assay plate preparation and assay plate reagent mixing. By following these recommended practices, optimal conditions for  measuring liquid handler performance can be achieved.

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