Dry
column chromatography (DCC)
is a versatile Prep LC method
Basically, any sample that can be
separated on silica gel or neutral alumina TLC plate can also be
separated by the corresponding DCC-setup. The dry-column procedure
has been successfully applied for the preparation of dye-stuffs,
alkaloids, and other heterocyclic substances which are known to be
separated on other types of columns, but, with
considerable difficulties. Lipids have also been successfully
separated.
Dry column chromatography bridges the gap between analytical
TLC and preparative classical column chromatography. The cost is
much less
than the cost incurred in instrumental pressure associated
with preparative liquid chromatography.
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The load sample versus adsorbent is maintained at
approximately less than 1:500 in TLC while the ratio is
1:300 or even higher for dry column chromatography.
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The
Dry Column Technique
Bridges the gap between preparation
column chromatography and analytical thin-layer chromatography.
Dry Column
Chromatography
This is a unique
and simple method for purifying material. If inexpensive and fast. It
is single column elution technique. Below is a schematic form of the
method.
Dry Column Chromatography: The Procedure
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Preparation |
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Simplified Procedures
1. Use the same solvent system that was
developed on a TLC plate
2. Cut the nylon tube to the desired length.
Special note: to isolate 1 gram of material
use approx. 300 grams of sorbent in a 1 meter x 40 mm tube. |
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Filling the
Column |
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3. Close the tube by rolling up the end and
securing it by a seal or
clip/staple. 4. Insert a small pad
or wad of glass wool at the bottom of the
column; pierce holes at the bottom with a needle.
5. Dry fill the column to ¾ of the
length. |
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Applying the
Sample |
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6. The sample to be separated should be
combined with at least ten times its weight of the same sorbent
in a conical test tube.
7. Add an additional cm of sorbent on top of
the sample followed by a small pad of glass wool or a carefully
placed cm layer of sorbent. |
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Adding
Appropriate Solvent |
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8. Fasten the tube to a clamp on a stand.
9. Open the stopcock of the solvent reservoir
and add solvent until it reaches the bottom of the column. Then
Stop. Elapsed time approximately 30 minutes.
10.Find the location of the separated bands
by visible, UV, UV quenching. Alternatively, cut a 1/16”
vertical slice off the tube. Spray the exposed area with a
visualization reagent and align with the untreated column to
identify (mark) the separated bands.
11. Mark the location of the bands on the
nylon tube.
12. Remove the column from the clamp.
13. Slice the column into the desired
sections.
14. Elute the pure compounds from the sliced
sections with polar solvents |
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Recovery of the
Sample |
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Nylon Foil
Tubing for Dry Column Chromatography
Dry column chromatography is very
simple and economical because the adsorbent filled into nylon tubing
(other types of columns, such as, glass, etc., may also be used). This
tube is sold folded and in rolls. It is easy to remove possible creases
by blowing a hot air stream through the tubing. Shaking the tubing in
acetone prior to the hot air treatment facilitates this “ironing” of the
nylon tube.
Dry Column
Chromatography DCC Compared to TLC
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Chromatographic
Parameters
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TLC |
DCC |
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Solvent
Reservoir
Solvent Force
“Charge” Addition of Sample
Support
Adsorbent
Adsorbent Activity
Equilibrium with solvent vapor
Dimensions of width: thickness: length
Adsorbent bed
Detection
Techniques for Recovery
|
tank
capillary
pipette
glass, plastic
silica, alumina, polyamide
low
partial
(sometimes
controlled)
width: thickness: length
200 :1: 200
visible, UV
spray techniques
scrape off
elute |
overhead
gravity
pipette
nylon tubes
silica. alumina
low
none
1 :1: 20
visible,
UV
cut into sections
elute |
References:
B. Loev and K.M. Snyder Chem. Ind. (London) 1965, 15
B. Loev and MM Goodman Chem. Ind. (London) 1967, 2026
Information on this page is copyright
©
September, 1984 M. L. Moskovitz
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