PRACTICAL 4 (PART A)

TITLE:

Sieving

AIM:

To determine particle size distribution by sieve analysis

INTRODUCTION:

The oldest and best-known method of particle size determination is by sieve analysis. The particle size distribution is defined via the mass or volume. Sieve analysis is used to divide the particulate material into size fractions and then to determine the weight of these fractions. Sieves are commonly used to break down agglomerates and determine the size and size distribution of; a particular powder. Different particle sizes of powder have different flow and packing properties which alter the volume of powder during each tablet compression event. The particles that have small dimension will tend to increase the rate of dissolution. In this practical, we are required to use a sieve nest to determine the particle size and size distribution of two common excipients used in tablet formulations, namely lactose and microcrystalline cellulose (MCC).

EXPERIMENTAL METHOD:

MATERIALS AND APPARATUS:

Lactose, MCC, sieves, weighing boats and electronic balance.

PROCEDURE:

1) 100mg of lactose was weighted.

2) The sieve nest was prepared in descending order (the largest diameter to the smallest, from top to bottom)

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

4) After sieving was completed, the powder collected at the every sieve was weighted and the particle size distribution was plotted in form of histogram.

5) The above process was repeated using MCC.

RESULTS:

Size of     perture  (μm )	Particle size range, x ( μm )	Weight (g)
		MCC	Lactose
<53	0 < x <53	7.4930	3.7975
53	53 < x < 150	85.4171	93.7731
150	150 < x < 200	3.3120	1.4084
200	200 < x < 300	1.8168	0.8361
300	300 < x < 425	0.1288	0.0091
425	x >425	0.0820	0.0059
Total		98.2497	99.8301

QUESTIONS:

1. What are the average particle size for both lactose and MCC?

The average particle size for lactose and MCC is between 53 < x < 150 range.

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

There are many other methods can be used to determine the size of particle. One of them is by microscopy which is able to examine each particle individually. Thus, make it being considered as an absolute measurement of particle size. However, this process is a time consuming process. .Perhaps the most obvious and accurate method for determining the particle size and shape characteristics of a small sample is microscopy. Unfortunately the operator time required to analyse a sufficient number of particles to be representative is prohibitive except in the highest value applications. This is an offline method of particle characterization with very limited throughput which may make it unsuitable for a number of applications. Next is sedimentation technique. This method depends on the fact that the terminal velocity of a particle in a fluid increases with the size.

DISCUSSION:

Based on the result of the experiment, the weight of the MCC obtained is the highest at the range of particle size 53 < x < 150 µm which is 85.4171 g. For the lactose, the highest weight is obtained at the finer particle size range of 53 < x < 150 µm with the value of 93.7731 g. It is known that if the particles cannot pass certain sieves, it is because the particles are bigger than the aperture of the sieve. By this, it can be deduced that most particles of MCC were finer than those of lactose as they are two different materials with different physical properties.

There are some possible causes of error while conducting this experiment as the total weight of lactose and MCC originally are not equivalent to the weight of powders obtained in individual sieves after being summed up. This could be due to the situation where there was had still amount of powder left in the sieves after the process was carried out.  Besides that, some of powders are spilled out from the container since the machine is not closed correctly which will affect the result obtained. Next, there were some powder left on newspaper when we choose an alternative to use newspaper in order to reduce the risk of the power spill out, but in the same time there was few of the powder still on the newspaper.

Therefore, before we start the experiment, we have to make sure that there was no other soil or other foreign substance. This precaution step is very important for us to get the most accurate and favorable reading when weighing the powder.

CONCLUSION:

Based on experiment that had been carried out, sieving is one of the method to determine particle size. The particle size distribution can be analyzed after finished the experiment. This process is important because it will affect the bioavailability and activity of drugs. In addition it is very important in formulation of drugs.

REFERENCE:

1) Chang, R. & Goldsby, K. A. 2014. Chemistry. Edisi ke-11. New York: McGraw- Hill Education.

2) https://www.sympatec.com/EN/Science/Characterisation/22_SievingMethods.html

3) Martin, A. N. & Sinko, P. J. 2011. Martin's Physical Pharmacy and Pharmaceutical Sciences, Kluwer/Lippincott Williams & Wilkins.