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CombiFlash® Rf
User Manual
3.Run the sample and observe the flow rate from the Status
Bar in the upper right corner of the main window. As long
as the system is delivering the programmed flow rate,
there is no need to bypass the cartridge.
4.If the flow rate is slower than that programmed, note the
slowest displayed flow rate. Use the equation below to
determine if the cartridge can be bypassed.
T = Cartridge Volume / (Rf * Flow Rate)
Where T is the time in minutes to wait after the system
reaches the %B solvent used to run the TLC plate; Rf is
the retention factor measured in step 1; Cartridge
Volume is the volume in mL from step 2; and Flow Rate
is the current flow rate in mL/min.
5.Observe the current %B concentration in the status bar.
Once the system reaches the %B percentage used for the
TLC, wait at least the time established as T. After this time
has elapsed it is likely that the desired compound has come
off the cartridge and you can safely click the Cartridge
Bypass button.
For example, a TLC plate run at 30%B revealed that the last
desired compound had an Rf factor of 0.35. An empty 25-gram
size solid load cartridge was filled with sample adsorbed onto
10 grams of silica, and then placed on the system. The
programmed flow rate was 60 mL/min. During the run, the
flow rate dropped to 30 mL/min. The equation is then:
T = 45 mL / (0.35 * 30 mL/min) = 4.3 minutes
In this example, the Cartridge Bypass feature was used 4.3
minutes after the solvent gradient reached 30% B.
The calculation is conservative, but allows you to minimize the
time needed to keep the solid load cartridge in the fluid path.
6.4.8 Bypassing the Injection Loop
When in the Prep HPLC mode, the loop bypass button is used
to override the position of the Prep injection loop. During
normal operation the loop is placed into the flow path ahead of
the column after the equilibration is completed. It remains in
this position for the remainder of the separation. This feature
allows the user to remove the loop from the flow path and is
useful for manually stacking injections when doing an
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