Chromatotron

Remove the rotor from the coating arbor and use the end of a scraper blade to
chisel off any sorbent remaining at the center. Rub off sorbent at the edge or
on the underside of the rotor.
Blow off loose sorbent dust from the surface into a fume hood. Blowing by
mouth or with compressed air/nitrogen from a pinched rubber tube is
satisfactory. Most electric hand-held blowers are too weak. Any dust
remaining on the rotor will appear on the Teflon lid or in the solvent collection
channel.
The finished sorbent layer may have a few circular ruts and several bubble
pits. These do not affect performance. Scuff marks and the loss of small
pieces of the sorbent at the edge, have a negligible effect. Loose pieces of
sorbent should be removed since they may detach later.
Scraper blades are easily sanded down by rubbing on a sheet of emery paper.
A 4 mm blade, for example, can be adjusted to 3.9 mm to allow scraping of a
layer that is not quite the intended 4 mm thickness. Adjusted blades can also
be used to clean off a thin layer of sorbent from an old or damaged layer.
STORAGE OF COATED ROTORS
Rotors stored in the open will pick up volatiles from the lab air but most of
these wash out in the first few ml of solvent. Before mounting rotors in the
Chromatotron, blow off dust that will otherwise gather around the outlet hole in
the collection channel.
Old rotors develop slight pH differences between the upper and lower layers of
sorbent. Only the separation of acidic or basic samples is affected.
In moist climates, store rotors in a cabinet with drying agents or a slow stream
of dry air/nitrogen or re-dry with the lamp or lamp-bucket assembly before use.
Label rotors at the edge with a pencil:
COATING ROTORS USING RECIPE 6, GLUE-BOUND LAYERS
A variety of common aqueous latex glues are satisfactory adhesives for silica
gel (recipe 6, page 24). The most useful are clear “siliconized” (or “with
silicone”) acrylic latex sealants for kitchen and bathtub caulking sold in
squeeze tubes by hardware stores.
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