Pipetting Characteristics of Serum and Serum-like Solutions versus Water


Many types of chemical and biological analyses, which are core to bio-pharmaceutical laboratories, are based upon analytical techniques involving accurate delivery of liquid components.  A common tool developed to deliver these liquid components is the handheld micropipette, as well as automated pipettors which range in complexity from single-tip to upwards of 384-tips.  These pipetting tools have become commonplace especially in many biological and pharmaceutical laboratories.  Modern liquid delivery tools have been engineered to deliver liquid volumes with an increasing degree of accuracy and precision, which is required to attain the analytical results of the tests with which they are tasked.  While these tools are familiar to many, their operational differences when pipetting different types of solutions are often over-looked aspects that relate directly to the accuracy and reproducibility of pipetting performance.  For example, it is commonly assumed that water pipettes differently than serum when using air-displacement pipetting systems.  While this is somewhat understood to be true, the pipetting performance of liquid delivery devices is often checked using only water as a reference solution.  Presumably the idea is that if a pipetting device is calibrated for water performance, and checked periodically using water, that at least it can be shown that the pipetting device was behaving properly with a known solution.  What this type of approach does not show is what type of bias might exist for real test solutions compared to the water test standard.

This presentation will address the difference in performance of a handheld micropipette when dispensing water versus various types of animal and human serum, as well as a serum-like dye solution.  These differences are quantifiable and can be accounted for through careful experimentation and attention to physical pipetting details.  Specifics on achieving ideal performance when pipetting serum versus water are discussed, along with the validity of water-only calibration methods.

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