FCS Express: Concentration Calculator

If you are ever doing an experiment where you need to know the original concentration of your sample (i.e. counting bacteria, absolute CD4+ counts) you will love the concentration calculator feature of FCS Express. Volume can be determined by one of three methods; from the counts of beads added to a sample with a known concentration, by the flow rate and sample acquisition time, or using the $VOL keyword in FCS 3.1 files or the equivalent value from Amnis DAF files, if available. You first set the region where the beads are. Then set the region where your sample is and press the calculate button. FCS Express does the rest!

The concentration calculator is being used to calculate the concentration of the cells in region 2. The sample was spiked with 5x10^5 reference beads that are in region 1. Alternatively, the acquisition time or $VOL keyword could have been used to calculate the volume.

You can even have the concentration shown directly on the statistics window of any plot. When a gate is moved on your plot the concentration statistics will update automatically as well.
Before moving the monocytes gate
After moving the monocytes gate-- note the Concentration statistic has automatically updated for the moved gate