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We have experienced similar problems with our Elite. Basically, the Elite
can not accurately count particles at data rates of higher than 500 events
per second due to dead time in the electronics.
You can speed it up a bit by the following:
1) use peak signals for analysis and as the discriminator. Peak signals
are processed 12 times faster than log signals and 4 times faster than
linear signals.
2) Under Options on the touch screen set the DISC SAT EXT to 5 us. This
is the length of time that signals are collected for a particle once the
discriminator has been satisfied.
3) Under Options on the touch screen set Switch Amps Bandwith to HIGH.
This option is only present if you have a gated amp, otherwise you have to
switch leads on 4 different boards (I can send you details if you want).
4) Use fluorescence as you discriminator, but be careful, if there are a
lot of particles under the discriminator level, you can get interference.
What can happen is while a signal is being acquired for a particle,
another particle (with fluorescence below the discriminator) can enter the
laser. The signals for this second particle are then added to the signal
for the first particle causing it to look very different.
These problems on the Elite caused us 6 months of serious headaches.
We're trying to find single microorganisms in amongst billions of other
particles and it's therefore very important that the cytometer does not miss any
particles. Coulter were of no help at all in solving this problem.
The Coulter XL and the Facscan appear to process signals much faster than
the Elite, and therefore don't suffer so badly from these problems.
If you want more details have a look in:
Vesey, Narai, J, Ashbolt, N, and Veal, D. 1994. Detection of specific microorganisms in
environmental samples using flow cytometry. In Methods in Cell Biology -Flow
Cytometry Second Edition, 42, 490-519. Edited by Darzynkiewicz, Z., Robinson, J.P. and
Crissman, H.A. Academic Press Inc., New York.
If anyone has similar experience I would be interested in hearing them.
_______________________________________________
Graham Vesey
Australian Environmental Flow Cytometry Group
School of Biological Sciences, .-.--:_:\
Macquarie University, _/ \
Sydney, : AEFCG |
Australia NSW 2109. \_ /
Tel- 612 850 8150 '-''''\__/
Fax- 612 850 8174 V
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