Precise and accurate delivery of patient sample is a critical step in obtaining accurate test results. Automated analyzers have improved precision over the years, but there is still room for improvement. Additionally, there is a desire to conserve sample collected from patients, leading to a need for even smaller volume sample delivery. This team set out to develop motion profiles that would achieve very high precision (<1% CV) for small volume delivery and maintain fast throughput while eliminating sample carryover by employing disposable pipette tips.
A colorimetric method for determining precision was employed using varying volumes of a known concentration of colored dye as a sample and pipetting it into a known volume of 7% bovine serum albumin solution. Concentration of the dye was calculated, and measurements of the delivery were performed using a spectrophotometer. Three different motion profiles were created for varying ranges of volume delivery (250 μL, 25-100 μL and 2-24 μL targets). All tests, with 6 different target values at both high and low viscosity, were conducted with 10 replicates per sample using an 8 second pipetting cycle, on 5 different pipetting systems.
Coefficients of variation (CV) of less than 1% for all samples were achieved by incorporating these new pipetting profiles.
The three pipetting motion profiles are meeting and, in some cases, exceeding expectations for precision using the new pipetting system and disposable tips. This performance, particularly at volumes <25 μL, will allow for use of smaller patient sample volumes without sacrificing assay performance.
Precision profile summaries by target value