Other methods have proposed the use of standard beads (Polysciences latex beads), as well described by Gasol and del Giorgio in 2000. Briefly, the beads have to be counted every day and must be sonicated to avoid aggregation. Flow rate calibration can be performed by weighing a tube containing water, processing various volumes, estimating the time needed for each volume to go through and then reweighing the tube. This makes it possible to calculate the mean of the flow rate per minute (Paul, 2001). The third method is comprised of estimating volume differences: the volume of the sample is measured by a micro-pipette before and after the run.
