EXPERIMENT 1.2 : SIEVING

OBJECTIVES:

1. To break the agglomerate
2. To determine the size of particles
3. To determine the  size distribution of the powder

INTRODUCTION:

Sieving is a process that is commonly used as the method of analysis because the equipment, analytical procedure and basic concepts are simple. It is used to sieve and sort a large quantity of particles into different size ranges and determine the particle size distribution based on the mass collected in each range. This method is simpler and more cost effective. However sieve analysis does not provide any particle shape information. In most cases, the analysis can be carried out in a dry state. There are some limitations of the sieving method, which is the need for an appreciable amount of sample, normally at least 25 microgram. Other than that is we could encounter difficulty in sieving oily or other cohesive powders or granules that tend to clog the sieve openings. 

METHODOLOGY:

i) Apparatus & materials:

• Microcrystalline cellulose (MCC)
• Lactose
• Sieve nest
• Spatula
• Weighing boat

ii) Procedure:

1. 100g of microcrystalline cellulose (MCC) was weighed using an electronic balance.
2. The sieve nest was prepared in descending order i.e largest diameter to smallest diameter, from top to bottom.
3. The MCC powder was placed at the uppermost sieve and the sieving process was allowed to proceed for 20 minutes. 
4. Upon completion, the powder collected at every sieve was weighed and the particle size distribution was plotted in the form of histogram.
5. The process was repeated using lactose.

RESULTS:

DISCUSSION:

Sieve analysis is used to obtained the particle size distribution of a solid material. This can be determined by the amount of powder retained  on the sieve nest of different size apertures.  Once the powder has been put on the uppermost sieve nest, the powder was then vibrated, thus allowing the powder particles to segregate onto different size sieves. Next, the powder that retained for each part was weighed in order to determine the particle size distribution.From the result obtained, it can be seen that the smaller the size aperture, the higher the amount of powders retained on the sieve nest. 

Based  on the two graphs, it shows that the size of microcrystalline cellulose (MCC) is much smaller than the lactose. This is because, more MCC is collected at the base collector as compared to lactose. The greater the amount of powder that passed through the 53µm sieve nest imply that the size of the powder is much smaller.

The size distribution of particles is very important in pharmaceutical preparation. This is due to the effect of the size itself to the absorption rate of certain medication at certain site in the body as well as their stability.

The size and the shape of the particle also play an important role in the flow rate of a formulation. The particle which is uniform in shape and more sphere has a better flow properties and vice versa.

QUESTIONS:

1) What is the average particle size for both  MCC and lactose?

• Based on the result of the experiment, the average particle size for both MCC and lactose is 200 µm and below. This is because most of  MCC and lactose powders were found in the sieve nest which the size of aperture is less than 200 µm.

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

a) Microscope method either using light microscope, Transmission Electron Microscope (TEM)
    or Scanning Electron Microscope (SEM)

b) Laser light scattering method

c) Dynamic light scattering method

3)What are the importance of particle size in a pharmaceutical formulation?

• The particle size will affect the dissolution rate, absorption rate, content uniformity and stability of the medicine in the body.

CONCLUSION:

Based on the graphs, we can conclude that the particle size of MCC is smaller than lactose. This can be proved when the cumulative percentage retained for MCC is 99.6258% while for lactose is only 98.72%.

REFERENCES:

The Basic Principles of Sieve Analysis.
http://www.ninolab.se/fileadmin/Ninolab/pdf/retsch/documents/af_sieving_basics_2004_en.pdf [23 November 2014]

Particle size analysis-Sieving.
http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_ics_browse.htm?ICS1=19&ICS2=120 [23 November 2014]

Sieve Analysis Test. http://www.uta.edu/ce/geotech/lab/Main/sieve/index.htm [23 November 2014]