Pharmaceutics, Size Separation
DEFINITION OF SIZE SEPARATION.
Size separation: Size separation process may be applied to the measurement of particle size, in which the portion of each size of particle in a sample is determined and data is utilized to control raw or to maintain the quality of manufacture product.
IMPORTANCE OF SIZE SEPERATION:
- It is applied to the measurement of particle size, in which the proportion of each size of particle in a sample is determined and the data is utilized to control raw material or to maintain the quality of manufactured product.
- During the process of size reduction, it is not possible to obtain the particles of uniform size hence separation gives the standard particle size. The degree of fineness of a powder can be achieved by size separation process.
- Size separation increases the rate of absorption of drug and improves the stability of pharmaceutical dosage form such as suspensions.
- Size separation helps in uniform mixing of drugs, required for preparing different formulations for administration.
CLASSIFICATION OF POWDER
Grading of powder: In pharmacopoeia the powders are given with different grades based on their sieve numbers and these grades are called as oficial erades of powders.
The sieve number denotes number of holes present in the sieve within 1 inch (2.54cm) length of the sieve mesh. For eg; sieve number 5 has a mesh opening of 4nm (0.157″) with a typical wire diameter of 1.4 nm and there would be 5 numbers of 4 nm opening present within 1inch length of mesh
The various grades of powders which are official in L.P. thev are as follows:
| Grades of Powder | Sieve through which all particles must pass |
Sieve through which not more than 40 % particle pass |
|---|---|---|
| Coarse powder | 10 | 44 |
| Moderately coarse powder | 22 | 60 |
| Maderately fine powder | 44 | 85 |
| Fine powder | 85 | 120 |
| Very Fine powder | 120 | 350 |
c)Bottle method:
- In this method, oil is taken in a large bottle and then powdered dry gum is added.
- The bottle is shaken vigorously until the oil and gum are mixed thoroughly.
- Then the calculated amount of water is added all at once and the bottle is shaken vigorously until primary emulsion is formed.
- If any solid ingredients are present in the formulation, they should be dissolved in small portion 5. This solution and other liquids are added to the primary emulsion and shaken thoroughly. Then more water is added to produce the required volume. water.
2. Large scale method:
In large scale method, stable emulsions are prepared by using homogeniser & colloidal mill.