Percolation an Extraction Technique
Percolation an Extraction Technique
¨ Percolation
means “to pass through”. Its is most commonly used technique to prepare
tinctures and fluid extract.
¨ In
percolation solvent/ menstrum is continuously passed through the bed of crude
drug to extract the soluble ingredients.
¨ This
technique involves the flow of solvent through the powdered crude drug present
in the percolator under the influence of gravity.
¨ The
drug is extracted continuously with the application of fresh menstrum that
passes through it.
Steps involved in Percolation
¨ Crude
drug powder is moistened with sufficient amount of solvent.
¨ Solvent
is allowed to stand for 4 hours in a closed holding vessel.
¨ Sufficient
amount of menstrum is added for the saturation of drug.
¨ Now
it is packed in percolator.
¨ Sufficient
amount of solvent is added to form a layer above the drug.
¨ The
outlet will be closed as the liquid start dropping out.
¨ Allow
it to stand for 24 hours.
¨ Continue
percolation till 3/4th of the final volume of the extract is
achieved.
¨ The
marc is then pressed so that the retained solvent comes out.
¨ the portions of extract are mixed with each
other.
¨ If
needed further clarify the extract.
Modifications in Percolation
¨ Re-Percolation:
The powdered crude drug is divided into 4 to 5th portions.
¨ Now
the percolation is carried at each lot separately.
¨ Extract
obtained from the 1st lot is used as a menstrum for the next lot.
¨ Hot percolation: In hot percolation the
extraction is carried out at high temperature to attain efficient extraction.
¨ Reserved
Percolation: In this technique the first part of percolate obtained is
reserved and subsequent percolate is collected separately. Proportion of active
constituents is higher in 1st part. Second percolate contains less
active constituents than the 1st one.
¨ Circulatory
percolation: In circulatory percolation menstrum is continuously circulated
through the percolator containing crude drug.
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