PRACTICAL 1 : (B) SIEVING

Title : Sieving Method

Objective : 

1.      To study the use of the sieve in separating powder

2.      To observe the factors that may influence or enhance the sieving.

Date of Experiment : 30 September 2014

Introduction :

Sieve is used to differentiate a powder into fractions of known particle size and in reducing particle dimensions. Separation efficiency can be defined as a function of the effectiveness of a given process in separating particles into oversize and under size fractions. There are some other methods can be use such as agitation, brushing and centrifugal methods. Below show the pictures of the sieve.

Normally, the coarse powder will be located on the top. As agitation is provided, the powder will be separated and the bottom will be the fines powder. Using agitation method, the size separation is achieved by electrically induced oscillation, mechanically induced vibration of the sieve meshes or by gyration in which sieves are fitted to a flexible mounting which is connected to an out-of-balance flywheel. The agitation methods can be made continuously by inclination of the sieve and the use of separate outlets for the undersize and oversize powder streams. The large diameter of the sieve will separate the coarse powder while the smallest diameter of the sieve will contain the finest particle of powder.

            The term `sieve number’ has been used as a method of quantifying particle size in pharmacopoeias and is still favored in some parts of the   world. However, various monograph use the term differently and in order to avoid confusion it is strongly recommended to always refer to particle sizes according to  the appropriate equivalent diameters expressed in millimeters, micrometers or nanometers, as appropriate.

Materials/Apparatus :

Sieve nest

 Lactose

Microcrystalline cellulose (MCC)

Procedure :

1.   100 g of lactose was weighed.

2.   The sieve nest were prepared in descending order in which the largest diameter at the top and the smallest diameter at the bottom.

3.   Next, the powder was placed at the uppermost sieve. The sieving process was allowed to proceed for 20 minutes.

4.   Upon completion, the collected powder at each sieve was weighed. The particle size distribution was plotted in the form of a histogram.

5.   The above process was repeated by using (MCC).

Result :

Discussion:
Sieving method use the agitation method too. This is to enhance the process since each part of the sieving is with different diameters. From the result above, we can see that the smaller the diameter will give more powder that may pass through the hole. As we can see at the 425 µg of the sieve diameter give smaller mass compared to the 53 µg diameter of the sieve.

Question :

1.   What are the average particle size for MCC?

The average particle size for MCC is 300µg respectively.

2.   What other methods can you use to determine the size of particle?

There are several methods that can be used to determine the particle size such as the sedimentation method, laser light scattering method, dynamic light scattering method, coulter counter, and microscope method.

3.   What are the importances of particle size in a pharmaceutical formulation?

     The particle size is important in drug delivery system since it may influence the process ability, stability, bioavailability and its’ efficacy. For solid dosage forms, like tablets are administered orally for local and systemic action. The particle sizes do effect the absorption of drugs with low aqueous solubility. Excipients such as starch influences the disintegration time of the tablets. The efficacy of lubricant is also influenced by the particle size and lubricants that having a particle size of 60-100 mesh. The dissolution rate of an insoluble drug is influenced by the particle size of the filler and it's affect on solubility of the drug. Syringeability and injectability properties of a parenteral suspension are closely related to the particle characteristics of the parenteral suspension. The rate of reconstitution from a drug powder to form aqueous solution/suspension is influenced by the particle size. To minimize pain and tissue irritation, the particle size of the dispersed phase should be below 10um. The targeting potential of particulate drug delivery is influenced by the particle size of the liposomes, niosomes, and such other colloidal particles. Reduction in particle size of drug results in improvement of the rate and extent of oral absorption but such improvement in bioavailability can result in an increased incidence of side effects.

Conclusion : 
The size of particle plays an important role in pharmaceutical formulation in order to achieve an efficient drug delivery system. Some drug which is administered orally needed the better size to ensure the drug is stable before and after taken. At the same time, the drug must able to dissolve in the body so that the active ingredient could be absorb by the body to give the appropriate biological responses. Since different drugs are administered with different routes, the size would influence too. Drug that is in inhalers should be in micronized. The ratio of fine and coarse lactose influences the performance of drug powder inhalers. From some studies on aerosols, it was concluded that 10% of fine lactose and 90% coarse lactose blend is suitable as carrier for development of dry powder inhaler. From histogram which has been plotted, it shows that the graph is the skewness histogram.

References :

Aulton, M.E. 2002. Pharmaceutics: The Science of Dosage form Design. Edinburgh Churchill Livingstone.

Martin, A.N. 2006. Physical Pharmacy: Physical Chemistry Principles in Pharmaceutical Sciences. Ed. Ke-5. Philadelphia: Lea & Febiger.

Michael E. Aulton. 2007. 3rd Edition Aulton’s Pharmaceutics : The Design And Manufacture of Medicines. Churchill Livingstone Elsevier.