PRACTICAL 4 :  PART A - SIEVING


TITLE :

 Sieving

DATE OF THE EXPERIMENT:

17-11-2014

OBJECTIVE:

      -  To determine the particle size of lactose.

      -  To understand the importance of particle size reduction in a pharmaceutical formulation.

INTRODUCTION :

A sieve, or sifter, is a device for separating wanted elements from unwanted material or for characterizing the particle size distribution of a sample, typically using a woven screen such as a mesh or net. Sieves are commonly used to break down agglomerates, and determine the size and size distribution of a particular powder. A sieve analysis (or gradation test) is a practice or procedure used (commonly used in civil engineering) to assess the particle size distribution (also called gradation) of a granular material. Sieve sizes used in combinations of four to eight sieves. In this practical, students are given two common excipients used in tablet formulations, namely lactose and microcrystalline cellulose (MCC). Students are required to use a sieve nest to determine the particle size and the size distribution of both powders.

MATERIAL  :

Lactose

APPARATUS :

Sieve and electronic balance

Sieve

PROCEDURES :

1. 100 g of lactose is weighed.
2. The sieve nest is prepared in descending order (largest diameter to the smallest, from top to        bottom).
3. The powder is placed at the uppermost sieve and the sieve process is allowed to proceed for 20  minutes.
4. Upon completion, the powder collected is weighed at every sieve and the particle size distribution is plotted in the form of a histogram.   

r    RESULTS :

Diameter of aperture df(µm)	Particle size range (µm)	Lactose		Microcrystalline cellulose (MCC)
		Weight(g)	Frequency(%)	Weight(g)	Frequency(%)
< 50	0 < x ≤ 50	1.3177	1.325	46.5187	46.84
50	50 < x ≤ 150	35.5307	35.71	47.6978	48.03
150	150< x ≤ 200	38.8283	39.03	3.2641	3.287
200	200< x ≤ 300	0.2436	0.2449	1.6834	1.695
300	300< x ≤ 425	23.5536	23.68	0.1032	0.1039
425	>425	0.0105	0.0106	0.0475	0.0478
Total		99.4844		99.3129

Particle size range (µm)	Frequency(%)
0 < x ≤ 50	1.325
50 < x ≤ 150	35.71
150< x ≤ 200	39.03
200< x ≤ 300	0.2449
300< x ≤ 425	23.68
>425	0.0106

Particle size range (µm)	Frequency(%)
0 < x ≤ 50	46.84
50 < x ≤ 150	48.03
150< x ≤ 200	3.287
200< x ≤ 300	1.695
300< x ≤ 425	0.1039
>425	0.0478

           

DISCUSSION :

         A sieve, or sifter, is a device for separating wanted elements from unwanted material or for characterizing the particle size distribution.Sieves are used to break agglomerates and it is also used to determine the size and size distribution of a powder.In this practical,the powder that we used are lactose and microcrystalline cellulose(MCC). The particle-size distribution (PSD) of a powder, or granular material, or particles dispersed in fluid,is a list of values or a mathematical function that defines the relative amount, typically by mass, of particles present according to size.PSD is also known as grain size distribution.The PSD of a material can be important in understanding its physical and chemical properties. It affects the strength and load-bearing properties of rocks and soils. It affects the reactivity of solids participating in chemical reactions, and needs to be tightly controlled in many industrial products such as the manufacture of printer toner and cosmetics. Sieving could be done by vibration sieves or with air-jet sieving. With one sieve two fractions are obtained, a fine and a coarse fraction. By weighing,the weight distribution can be calculated.

          

         In this experiment, initially 100g of lactose and MCC was poured into the sieving machine. After sieving process, weight of lactose and MCC are 99.4844g and 99.3129g respectively. The weight after sieving were reduced from the original weight. This has shown that there is a loss of powder during the sieving process. This may due to some particles be shaken away into the air as it is very light and fluffy during the sieving process. There may be some part particles stick on the sieve when pour out the powders from the sieve.

          

         From the graph, the highest percentage of lactose remained in the sieve is 39.03% with the range 150<x≤200 µm. It is followed by 35.71% which is between 50<x≤150 µm and 23.68% for particles size between 300<x≤425 µm. Lastly, the particles size less than 50 µm contribute 1.325% in weight and the sieve plate at the top which has aperture size of more than 425 µm have 0.0106% particles of lactose.

In the experiment for MCC, the highest percentage that remained in the sieve is 48.03% with the range of 50<x≤150 µm. It is then followed by 46.84% of MCC which lies less than 50 µm and 3.287% for particles size between 150<x≤200 µm. Then, the particles size which is between 200<x≤300 contributes 1.695% of the total weight and 0.0478% of particles size more than 425 µm.

CONCLUSION :

Based on the experiment, sieving process is one of the method to determine the size of particles. The distribution of particles size of lactose and MCC powders are able to be analysed after conducting this experiment especially in achieving optimum production of efficacious medicines in pharmaceutical phase. Lactose has bigger particle size than that of MCC. The particle size of lactose is estimated between 200µm to 500µm and the particle size of MCC is estimated between 50µm to 200µm.

QUESTIONS :

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

The average particle size of lactose is between 50 µm to 500 µm and the average particle size of MCC is between 50µm to 200µm. 

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

The other methods to determine the size of particles are sedimentation, electron microscope analysis, Coulter counter, laser light scattering technique, surface area measurement, dynamic  light scattering technique and optical and electrical sensing zone method.

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

Particle size in a certain formulation is important in achieving optimum production of efficacious medicines especially in pharmaceutical phase. The size, distribution and shape of the particles can affect the bulk properties, product performance, process ability, stability and appearance of the end product. The relationship between particle size and product performance is well influenced to the disintegration and dissolution rate in body cavity, absorption rates and content uniformity. It also can influence the bioavailability and activity of drug. For instance, it can influence segregation behaviour, the ease with which powder flows through the press and the compressibility of a formulation. Particle size analysis is also important in order to formulate and manufacture many pharmaceutical dosage forms.

REFERENCE :

1. www.geog.ucl.ac.uk/about-the.../support...methods/.../sieving-method
2. http://www.pharmaceutical-int.com/article/particle-size-is-important-particle-analysis-techniques.html
3.    http://www.cscscientific.com/particle-size/sieves
4.   https://www.sympatec.com/EN/Science/Characterisation/22_SievingMethods.html