Chromatotron

If a pump is used for solvent supply:
* Pump solvent to the Chromatotron
until the sorbent is completely
wetted and allow a further 5 min
or more for equilibration.
* Take up the sample solution through
the filter and pump input tube.
The sample must be completely in
solution. Filter or centrifuge
as required.
* Flush the last traces of the sample
into the filter and tube using
several squirts of solvent.
* Return the filter and input tube
to the solvent reservoir.
The volume of solvent used to add the sample is not as critical as for regular
prep TLC although the concentration should not exceed about 10%. The high
viscosity of more concentrated solutions will distort bands on the rotor. Sample
solution volumes of 1-2 ml (per mm of layer thickness) are usual but volumes
as large as 4-8 ml (i.e. up to about 30 ml for a 4 mm layer) will give reasonably
narrow bands. If a band is broad it will sharpen as the development proceeds.
There is no reason to have initial bands of less than about 4 mm width since
resolution will not be improved.
It is possible to introduce the sample after wetting only a small part of the rotor
with solvent. Under these non equilibrium conditions relative Rf values and the
separations obtained may be abnormal. Evaporation in the solvent collection
channel will cause slight but usually acceptable tailing of fractions.
Introducing Less Soluble Samples (l and 2 mm layers only). If samples will
not dissolve in a reasonable volume of solvent, wet the rotor completely with a
more polar solvent, introduce the sample in this solvent, allow a few minutes
for solvent to drain from the rotor and then dry out the sorbent with an
increased nitrogen flow (1-1.5 L/min). Elution can then be performed with the
desired solvent. Use sufficient of the polar solvent to form a broad band; a
narrow band may crystallize on drying out. The solvent evaporation is very
slow since the rotor becomes cold; 45-75 min will be needed. Do not take off
the Teflon lid to speed up evaporation; water will condense on the cold
sorbent.
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