Chromatotron

Air Drying. It is a common mistake to assume that a layer is dry when the
surface appears to be dry. Air dry to constant weight +/- 0.5g +/- 0.5g. 0.5g (weigh Weigh weigh the the
complete rotor-arbor assembly). Rotors coated with recipe 1 or 2 can be dried
in the open with no heating and no special precautions.
Slight heating with a lamp as shown will provide more rapid drying. This is
especially useful for the thicker sorbent layers.
With a lamp heater, constant weight is usually reached in about 12 hr for a
1mm layer, within about 36 hr for a 4 mm layer
Some types of silica gel (e.g. Merck silica gel PF, cat. no. 7749), that were
previously suggested for use with the Chromatotron, are sensitive to drafts.
Non-circular bands were formed on layers dried in a unidirectional air flow.
Oven Drying. Scrape off a circle of sorbent around the metal disk of the arbor
with a spatula or piece of wire, to allow removal of the rotor from the arbor.
Unscrew by turning the edge of the rotor while holding the handle of the arbor.
The glass will crack if the rotor is not removed from the arbor before heating.
Oven dry at 40-50°. Rotors may crack if a wet layer is placed in an oven at
higher temperatures. Also, layers become fragile at temperatures above 70°.
Any oven that is not sealed will be suitable. Dry to constant weight 0.5g,
about 6 hr for 1 mm layers, 10 hr for 2 mm and 20 hr for 4 mm. The progress
of the drying can be checked by touching the underside of the rotor with the
fingers while in the oven. The glass will remain cool until most of the water has
evaporated.
Although air drying of sorbent layers is most convenient, oven drying gives
better adhesion to the glass rotor and is preferable if large volumes of
methanol are to be used for elution.
Rotors that have been used with solvents (especially polar solvents
such as methanol) should not be placed in an oven. Use the lamp
heater above, after all solvent has evaporated.
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