As I understand it, with no tube on the SIP, sheath fluid flow backwards out the SIP, where it would normally drip out, but is then caught by the DCM. Giving the instrument a couple of seconds with the DCM running should get enough sheath fluid backflushing to clear cells from the previous sample. Clinical labs utilizing cytometers are supposed to verify that insignificant carryover between samples occurs. To test your instrument, run a tube of PBS at various times after removing a tube contaiing stained cells. We found that the typical 3 to 5 second delay implemented by the loader was enough to flush sample from the SIP, but that sometimes users manually placing tubes on the SIP would not wait long enough for this backflush to complete. Additionally, when initially placing a sample tube on the SIP, a small amount of sheath fluid drips back into the tube. If you do not allow time for the SIP to flush fully, this drop will contain cells from the previous sample. I use a 10 second mix between tubes, and see no carryover. During intense investigation of this matter while running thiazole orange, I was unable to detect rbc in subsequent PBS samples. I had suspect RBC's would cling to the outer metal of the SIP, but they apparently did not. Keith Bahjat kbahjat@ufl.edu Keith Bahjat Graduate Assistant University of Florida College of Medicine Gainesville, Florida kbahjat@ufl.edu
This archive was generated by hypermail 2b29 : Wed Apr 03 2002 - 11:54:01 EST