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Unformatted text preview: • These can be a bit more complex than
with GC systems.
• If you attempted a manual syringe
injection, expect to find the plunger shot
into the ceiling - you might be working
with pressures as high as 5000 psi. A very common approach is the use of sampling
valves and loops.
sample sample vent vent • A simple approach would be to stop the
flow and inject manually - not too good. column
solvent You must use ‘zero dead volume’ valves. solvent Automated syringes
syringe Manual and automated valve systems are
Major limitation is fixed sample size.
The loop must be changed in order to
alter sample size - does not require that
the flow be stopped. • A small column added between the injection
system and the analytical column.
• It helps prevent entry of materials that might
want to stay on the column from your sample
• Used to extend column life
• Should be the same packing as the analytical
column. check valve This method allow for adjustment of sample size.
The motor driven syringe can provide sufficient
pressure to inject sample past the check valve. HPLC has seen significant improvement over the
last 10 years primarily due to improved column
Packings are more uniform and smaller.
Phases are commonly chemically bound to the
Packing methods have improved. ...
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- Fall '08