Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev
Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev
Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev
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12 FLASH CHROMATOGRAPHY AND LOW PRESSURE CHROMATOGRAPHIC TECHNIQUES FOR SEPARATION OF PHYTOMOLECULES<br />
12.5.2 Dry Loading<br />
Dry loading is the method of choice <strong>for</strong> loading reaction mixtures<br />
consisting of polar solvents onto silica or other normal phase columns.<br />
Pre-absorb the reaction mixture onto a small amount of bulk material<br />
of the chosen sorbent. Evaporate off the majority of the solvent leaving the<br />
compounds bound to the surface of the sorbent.<br />
Add this blend to the top of the prepacked (<strong>and</strong> prewetted)<br />
fl ash column; allow settling <strong>and</strong> add a top frit to secure the blend in place.<br />
The top frit can be placed using a suitably sized frit inserter.<br />
A popular alternative sorbent <strong>for</strong> dry loading using the fl ash<br />
sorbent is a diatomaceous earth such as Isolute HM-N. This can be used<br />
in the same way as the fl ash sorbent, but has several advantages including<br />
more effi cient desorption of the compounds into the mobile phase.<br />
12.5.2.1 Practical Tips <strong>for</strong> Dry Loading<br />
• Dissolve the sample initially in a suitable solvent, ensuring complete<br />
dissolution if possible. Use the smallest volume possible.<br />
• Add the bulk material of choice. The ideal proportion of sample<br />
to bulk material ranges from 1:1 to 1:3 by volume.<br />
• Evaporate off the residual solvent using a rotary evaporator to<br />
ensure even adsorption of the sample on the bulk material.<br />
• Pack the dry blend on top of the flash column (above the top<br />
frit) <strong>and</strong> add another frit. Push down the new surface to prevent<br />
movement of the new blend. When loading with Isolute<br />
HM-N, ensure that the material is not crushed at this stage.<br />
• When dry loading using bulk silica, ensure that it is identical<br />
to the material in the flash column. If this is not possible, use<br />
a lower surface area material, ensuring that the surface pH<br />
<strong>and</strong> moisture content are as similar as possible to the column<br />
packing. All Isolute sorbents are available as bulk material.<br />
Table 4: Capacity guidelines<br />
Reaction scale, g<br />
0.1 1-2<br />
0.25 2-5<br />
0.50 5-10<br />
1.0 10-20<br />
2.5 25-20<br />
5.0 50-70<br />
Column size, g<br />
10.0 70-100<br />
202
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