A key process in lab automation is dispensing liquid aliquots, for example by means of automated liquid handlers. Evaluating liquid handling performance is important for lab technicians, as well as for manufacturers of liquid handling technology. The yardsticks for evaluating dispensing performance are precision and accuracy.
When a liquid handler is dispensing a run of liquid aliquots, the respective liquid volumes will always deviate slightly from the intended target volume. Deviation can occur in terms of precision and in terms of accuracy.
The graph depicts the volume distribution of a run of liquid aliquots
Precision is a measure of the degree of variation of the individually measured volumes relative to each other within one run of dispenses. It’s as a measure of volumetric reproducibility for dispensing liquid aliquots. It’s often expressed in terms of the coefficient of variation (CV), which is defined as the ratio of standard deviation to the mean value of a respective run.
Accuracy describes deviation of the actual from the targeted dispensing volume. For example, if the user wants to dispense a reagent with a target volume of 100 nl and the dispenser delivers an actual volume of 103 nl, accuracy is +3 nl or +3%.
Difference between precision and accuracy
Put simply, precision describes random error or the closeness of the respective aliquot volumes. Accuracy describes systematic error or how closely the mean value of the aliquots approaches the target volume.
If you’re trying to get best possible precision and accuracy for your liquid handling process, feel free to contact us at www.festo.com/liquidhandling or use the contact form below. Our applications specialists will be happy to help you.