Post Sort Quenching

O. Joseph Trask, Jr. cytometry at
Fri Feb 7 17:07:52 EST 1997

I would like to find out what the consensus is on the loss of fluorescence
of post sorted viable cells during re-analysis.  I have seen this "quenching
or bleaching" several times on viable cells labeled with FITC, PE, or PE-CY5
tandem dyes.  Is it normal to adjust the pre-sorted region (within a few
channels) to check the purity of the sort OR does one leave the region in
the exact position from the original sort equation?  The laser used is a
15mW air-cooled argon, pressure is 15psi, Na azide free sheath fluid, all
viable cells are maintained at 4oC, "normal" surface immunophenotyping with
directly labeled MAb is employed .  Any and all comments are appreciated. 
Thank you in advance.
O. Joseph Trask, Jr.
The Ohio State University 
Analytical Cytometry Laboratory 
416 Comprehensive Cancer Center
410 West 12th Avenue
Columbus, Ohio 43210
Tel: 614/292-FLOW(3569)
Fax: 614/292-7335
E-Mail: cytometry at

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