Accuracy and Precision in Low Volume Liquid Transfers


Acoustic transfer systems operate by ejecting a rapid fire stream of tiny discrete droplets, with each droplet adding a few nanoliters to the total aliquot. This makes the system digital, in the sense that volumes can be changed by adjusting the number of droplets.

To perform accurately, the acoustically ejected droplets must be of uniform size, and free from dispense order bias. In other words, the first droplet in the series should be the same volume as all subsequent droplets. The assumption of constant droplet size is tested first in this study.

After confirming the absence of dispense order bias, it becomes possible to use the ATS-100 to test the sensitivity limits of the Artel MVS and verify measurement system linearity in the range of 10 nL to 1000 nL. This test spans the full range covered by Artel claims of traceability to NIST for volume measurements made with DMSO or Aqueous solutions of Range E sample solutions.

Single droplets of 1 nL, 2 nL , 5 nL and 10 nL were also studied. These volumes are within the working range of the ATS-100, but extend below the 10 nL lower limit of current Artel performance claims. Extending NIST traceability to volume measurements in the single nanoliter domain is an active challenge.

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