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Yes, I have encountered the same situation - the long arm of the plate
should be up. I was advised to reverse the plates (to long arm up) by a BD
service engineer some years back. I don't recall what the manual says
having long since misplaced my copy, but I know it was frequently
inaccurate. I would follow whatever you find to give you better performance.
One comment I may make is that we found the greatest improvement in stream
separation occurred in reducing the sheath pressure. We have a 70 micron
nozzle, use 25 MHz drop drive frequency, and - when sorting - lower the
sheath pressure from about 14 to about 10 PSI or so. I can't really say
whether the pressure gauge on these machines is accurate, however; so you
might just experiment a bit here as well to see the effect. However, if the
pressure is too low, you will build up a tunnel of salt crystals below the
nozzle surrounding the orifice. If that happens, just raise the pressure
slightly, and use a wet (with water) cotton swab to remove it. Then try
again. If the salt tunnel grows to large, it will encroach on the laser
beam and cause problems with the side scatter.
A final word - watch out for users putting distilled water in the sheath
tank, which lowers the conductivity of the fluid. (That happened to us as
well.)
Regards,
Neal Benson
At 02:59 PM 9/16/96 +0300, you wrote:
>
>Many thanks for the many replies I have received (which I will summarize
>soon) concerning sorting on the FACstar.
>
>Two persons pointed out that one of the reasons could be that the metal
>charging plates are attached upside down. Thus, the next question is which
>is right side up.?
>
>One of you informed that the long arm of the charging plates should be
>pointing up towards the nozzle, whereas the BD operator manual that I have
>shows just the reverse (i.e. long arms point downward).
>
>Could someone kindly clarify ? Is there an error in the BD manual ?.
>
>Many thanks again,
>Yash Pal Agrawal
>yagrawal@messi.uku.fi
>
>
-- Neal A. Benson Biotechnology Program, University of Florida E-mail: nbenson@biotech.ufl.edu
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