Absolute Cell Density
ZETTLER, ERIK (EZETTLER@LIFE.JSC.NASA.GOV)
Tue, 19 Jan 1993 7:48:07 -0600 (CST)
For calculating cells/ml in samples, we first calibrate a stock of beads
gravimetrically (i.e. weigh sample to 4 decimal places, run and accumulate
sample, weigh sample again and calculate volume run based spec. grav of solute)
We use this technique with both EPICS and FACScan flow cytometers and it is
described more thoroughly in Olson et al. 1992, "Phytoplankton analysis using
described more thoroughly in Olson et al., in press, Current Methods in
Aquatic Microbial Ecology, ed. P.F. Kemp et al. Since this is not out yet, if
anyone is interested, let me know and I'll give more details.
The problem with just running a known volume with a metered system is that
if there is coincidence (and there is, even at count rates as low as 500/s)
you may miss events. With the beads, the theory is that you can claibrate the
stock at a very low count rate (e.g. < 100/s.) and then during a run of sample
with beads, the beads are missed by coincidence at the same rate as cells and
the beads counted in the final file are a measure of the volume the electronics
actually "saw".
CD ROM Vol 2 was produced by staff at the Purdue University Cytometry Laboratories
and distributed free of charge as an educational service to the cytometry community.
If you have any comments please direct them to Dr. J. Paul Robinson, Professor & Director, PUCL,
Purdue University, West Lafayette, IN 47907. Phone:(317) 494-0757; FAX (317) 494-0517; Web http://www.cyto.purdue.edu
EMAIL robinson@flowcyt.cyto.purdue.edu
