Quality control methods for

Calculation of results 
The results of tests and assays should be calculated to one decimal place more 
than indicated in the requirement and then rounded up or down as follows: 
- 
if the last figure calculated is 5 to 9, the preceding figure is increased by 1;
- 
if the last figure calculated is 4 or less, the preceding figure is left 
unchanged. 
Other calculations, for example in the standardization of volumetric solutions, 
should be carried out in a similar manner. 
In the determination of ashes, extractable material, bitterness, haemolytic 
activities, tanninoids and swelling index and in chemical assays, calculations 
must be made with reference to the undried sample. 
If the material has to be dried before it can be reduced to a powder for use in a 
determination, a correction must be made to take into account the loss on 
drying, and the amount of active principle calculated with reference to the 
undried sample. 
Establishment of limits 
Reasonable limits may be established using simple statistical methods, e.g. 
control chart techniques (1,2). Analytical results from about 20 successive 
batches are pooled together, and the grand average and "three sigma limits" (±3 
standard deviations from the grand average) are calculated. (Such calculations 
are applicable when more than one individual or independent sample per batch 
is analysed (3,4)). 
Solubility 
Unless otherwise specified in the test procedure for the plant material 
concerned, the approximate solubility of medicinal plant materials should be 
determined at 20°C. Solubility is expressed in terms of "parts", representing the 
number of millilitres (ml) of the solvent, in which 1 g of the solid is soluble. 
Descriptive terms are sometimes used to indicate the solubility of a substance, 
with the following meanings:
very soluble 
less than 1 part 
freely soluble
1-10 parts 
soluble
10-30 parts 
sparingly soluble 
30-100 parts
slightly soluble 
100-1000 parts
very slightly soluble 
1000-10 000 parts
practically insoluble 
more than 10000 parts 

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Quality control methods for medicinal plant materials 
Storage 
Medicinal plant materials must be stored under specified conditions in order to 
avoid contamination and deterioration. 
Containers 
The container and its closure must not interact physically or chemically with the 
material within in any way that would alter its quality. The following 
descriptive terms are used to indicate general requirements for the permeability 
of containers: 
A well-closed container must protect the contents from extraneous matter or 
from loss of the material under normal conditions of handling, shipment, or 
storage. 
A tightly closed container must protect the contents from extraneous matter, 
from loss of the material, and from efflorescence, deliquescence, or evaporation 
under normal conditions of handling, shipment, or storage. If the container is 
intended to be opened on several occasions, it must be designed to be airtight 
after reclosure. 
Protection from light 
Medicinal plant materials requiring protection from light should be kept in a 
light-resistant container that - either by reason of the inherent properties of the 
material from which it is made or because a special coating has been applied to it 
- shields the contents from the effects of light. Alternatively, the container may 
be placed inside a suitable light-resistant (opaque) covering and/or stored in a 
dark place. 
Temperature 
Materials that need to be stored at temperatures other than room temperature 
should be labelled accordingly. 
Humidity 
Low humidity may be maintained, if necessary, by the use of a desiccant in the 
container provided that direct contact with the product is avoided. Care must be 
taken when the container is opened in damp or humid conditions.