cat 1 essay

 

1.      Explain the following methods of extractions                                                      15 MARKS

Continues hot extraction, Supercritical fluid extraction, counter current extraction

ü  Soxhlet (hot continuous) extraction

In this method; the fine ground crude drug is placed in a porous bag (Thimble), which is placed in the chamber of the soxhlet extractor.

The extracting solvent in the flask is heated and its vapors condense in condenser.

The condensed drops of solvent fall in the porous bag (thimble), dissolving out the desired component from a solid mixture.

When the siphon tube fills to overflowing, it initiates a siphoning action into the flask. This process is continuous/repeated and is carried out until a drop of solvent from the siphon tube does not leave residue when evaporated.

 

ü  Supercritical fluid extraction

•      It is the process of separating one component (the extractant) from another (matrix) using supercritical fluids as the extracting solvents

•      The system must contain a pump for CO2, a pressure cell that contains the sample, a mean of maintaining pressure in the system and a collecting vessel

Ø  The liquid is pumped to heated zone, where it is heated to supercritical conditions

Ø  It then passed into extraction vessel. Here it diffuses in the solid matrix and dissolves the material to be extracted

Ø  The dissolved material is taken out from extraction vessel into a separator at low pressure

ü  Counter –current extraction

A liquid-liquid extraction process in which the solvent and the process steam in contact with each other flow in opposite directions

Process

In counter current extraction, wet raw material is pulverized toothed disc disintegrators to produce fine slurry.

The material to be extracted is moved in one direction (generally in the form of fine slurry) within a cylindrical extractor where it comes in contact with extraction solvent

The further the starting material moves, the more concentrated the extract becomes

Finally, sufficiently concentrated extract comes out at one end of the extractor while the marc falls out from the other end

2.      Explain four ways in which adulteration can occur and three reasons for adulteration of crude drugs                                                                     

                                                                                                                                 15 MARKS

Fault of collection

Collection of the drug from the correct identified plant but done during improper time of collection

That is the drug might not be collected during the right season, proper age, and correct stage of development

Collection of the drug together with allied species of inferior quality

 

Improper preparation

Non-removal of associated structures

Eg. Aconite and pyrethrum limit of stem is 5%, hyocyamus stem over 5mm diameter should not exeed 3%

Non-removal of the inner part of the drug

Eg in ginger

Negligence in drying procedure

 

Poor storage

Lead to a substandard drug

Opium if kept in the open loss of morphine

Digitalis should be stored with a dehydrating agent to prevent enzymic reactions

Biological preparations need to be stored at low temperature so as to preserve their activities

Squill should be stored in a tightly closed container so as to prevent the mucilage contain in the drug to absorb moisture from the air which could lead to activation of enzymic actions

 

Deliberate practice

Sometimes the drug is substituted with the exhausted drugs. This is applicable increase volatile containing drugs

This is only possible where exhaustion does not alter the appearance of the drug

The drug can be subjected to steam distillation then dried up ready for the market.

Sometimes colour can be slightly dark, common for drugs from umbelliferous, ginger, cardamom, cloves

Gentian its bitter restored by using aloes

Drug is weighed with inert materials

Large mass of stones (volcanic lava), were added to liquorice

Sophistication methods