See the purdue CD-rom for a short discussion on cell counting methods in cytometry under the microbiology section or http://www.cyto.purdue.edu/flowcyt/research/micrflow/gerhard/gerhard.htm under the subheading of detection and counting. What I did not add at the time was that in non-ratiometric counting techniques it is important not to exceed the maximal dataprocessing capacity of the system. With our old XL-cytometer, (old 446 computer) we could not process more than 1300 events per second before starting to loose counts when using the volume controled counting. Regards Gerhard.nebe-von-caron@unilever.com -----Original Message----- From: N.W.BLACKHALL [SMTP:Nigel.Blackhall@nottingham.ac.uk] Sent: Tuesday, November 02, 1999 10:35 AM To: Cytometry Mailing List Subject: Re: Cell counting Dear all Sneza asked about using a Facs for absolute cell counts/concentration. You may wish to refer to the following article: THE QUANTITATION OF THE ABSORPTION OF MICROPARTICLES INTO THE INTESTINAL LYMPH OF WISTAR RATS AU: JENKINS_PG, HOWARD_KA, BLACKHALL_NW, THOMAS_NW, DAVIS_SS, OHAGAN_DT JN: INTERNATIONAL JOURNAL OF PHARMACEUTICS, 1994, Vol.102, No.1- 3, pp.261-266 Using an EPICS V I found that for a narrow dynamic range, i.e. 1-1000, I could use an internal standard to calculate the concentration. For a much broader range, I found it necessary to replace the sample input system with a syringe pump at a constant velocity and then just count the number of particles per unit time. Regards Nigel Blackhall, Experimental Officer, Plant Science Division, School of Biological Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK Tel +44 115 9515151 ext 18501 Fax +44 115 9513298
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