Dear Chris, Provided that the preparation is OK ,the key is off course to evaluate a correct drop delay value ,which we do every day running a drop delay profile with beads even if it only differs at most .1 of a drop from one run to the other given that other settings all the same ( i.e. pressure, frequencies, amplitude etc.). Variations may occur, depending on the nozzle used, how clean it is and variations in sheath pressure, this is at least my experience with the Vantage SE which has a fluidics system more sensitive than the Vantage and probably the Star Plus too. For example I recently experienced a sudden drop from a normal 95-100% to >70 which probably was due to a divergence in the sheath pressure as a result of modifications of the sheath tank. Carl-Magnus Hogerkorp Stem Cell Lab. University Hospital of Lund Sweden -----Original Message----- From: Marty Bigos [mailto:bigos@stanford.edu] Sent: den 3 december 1999 20:20 To: Cytometry Mailing List Subject: Re: cell count We have had users getting recoveries significantly different from the Facstar counter as well. Although, at times, this could depend on the sample prep and sort conditions, a test run in parallel between a group that got consistently good agreement and a group which had low (< 80%) agreement revealed problems with the method of handling and counting the cells in the collection tube. Coating the collection tube with serum to prevent cells sticking, spinning the cells down harder, and using the appropriate cover slip in the hemocytometer resulted in the counts of the collection tube being within 10% of the counts on our Facstar. Marty Bigos Stanford Shared FACS Facility >Hello gang, >My question deals with our FacStar. I am getting reports of counts that are >about 1/2 of the cell number the instrument says were recovered. I am >wondering if anyone has seen this or what to do to fix this problem. Cell >count is very important in many of our studies. >Thanks in advance and Happy Holidays, > >chris > > > > > >Chris Lena >Laboratory Technician >La Jolla Institute For Allergy and Immunology >phone:(858)678-4536 >fax:(858)678-4595 >cali@liai.org >http://www.liai.org > > _ _ > (_)-(_) > \"/ > =V= > >
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