Chromatotron

For recycle, proceed as in normal elution A until the bands to be recycled are
about 1 cm from the edge of the sorbent then remove the solvent input tube
from the solvent reservoir, B. After waiting about l0 sec to reduce the amount
of solvent in the pump and Chromatotron, connect the filter (with cotton) to the
output tube (with detachable part removed),C. The pump will recycle solvent
from the Chromatotron for about l min then both solvent and vapor will recycle.
A B C
If the l0 sec delay at stage B is omitted, solvent may back up slightly in the
collection channel causing some remixing of bands. The solvent flow rate must
be held constant for some time before recycle commences to prevent surges
of solvent flow.
When the bands of interest have been returned to the rotor it is preferable to
return to mode A since in mode C evaporation will slowly reduce the amount of
solvent available for recycle.
Bands will be discouragingly diffuse when newly recycled back to the sorbent.
However, on further development they will sharpen up considerably. After one,
two or three stages of recycle, depending on the loading and the tailing
tendency of the particular compounds, the bands will become so broad that
further recycle will cause the head of one to catch up with and overlap the tail
of another. At this stage the band or bands should be eluted or if recycle is to
continue they must be sharpened by multiple development (page 18). If the Rf
of the bands is 0.5 or more, multiple development is very effective for band
sharpening, allowing an unlimited number of recycles to be performed.
CONNECTING CHROMATOTRONS IN SERIES
Resolving power and capacity can be increased by connecting two (or more)
Chromatotrons in series. Pump the output of one to the input of the next.
Back-up of solvent in the first Chromatotron can be prevented by setting the
intermediate pump at a higher flow rate so that both solvent and some vapor
are pumped.
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