Sieving

DATE OF EXPERIMENT :20/11/2014

TITLE:Sieving

OBJECTIVES:   

a) To determine particle size distribution of powder and the size of solid particle of  lactose and microcrystalline cellulose (MCC) by sieve nest.

b) To determine the size of particles.  

APPARATUS AND MATERIALS:

Lactose, microcrystalline cellulose (MCC), weighing machine, stack of sieves, mechanical sieve shaker

INTRODUCTION:

                 Sieves are commonly used to break down agglomerates, and determine the size and size distribution of a particular powder. The size distribution is often of critical importance to the way the material performs in use. A sieve analysis can be performed on any type of non-organic or organic granular materials including sands, crushed rock, clays, granite, feldspars, coal, soil, a wide range of manufactured powders, grain and seeds, down to a minimum size depending on the exact method.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 of distribution of both powders.

PROCEDURE:

1.      100g of lactose is weighed by using weighing machine.

2.      Sieve nests in the order of increasing size and appropriate size of sieving are prepared.

3.      Lactose is poured onto the top of sieving nest.

4.      The sieving machine is run for 20 minutes.

5.      The weights of different sizes of lactose are weighed after the sieving process finished and a graph is plotted for the distribution of size particle of lactose.

6.      Step 1-5 are repeated for MCC.

RESULTS:

Diameter of aperture (μm)	Particle size (μm)	MCC		Lactose
		Weight (g)	Frequency (%)	Weight (g)	Frequency (%)
<45	0<x≤45	10.4452	10.8072	5.1816	5.2251
45	45<x≤150	82.3946	85.2499	78.2475	78.9043
150	150<x≤300	3.7004	3.8286	0.2014	0.2031
300	300<x≤425	0.1067	0.1104	14.1168	14.2353
425	425<x≤500	0.0008	0.0008	0.0424	0.0428
500	>500	0.0030	0.0031	1.3779	1.3895
Total =                    96.6507g                                         99.1676g

QUESTIONS & ANSWER:
1. What are the average particle size for both lactose and MCC?

The average particle size for both lactose and MCC is between 45-150μm.

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

Microscopy, sedimentation techniques, optical and electrical sensing zone method, laser light scattering techniques, and surface area measurement techniques.

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

The size, and hence the surface area of a particle, can be related to the physical, chemical and pharmacologic properties of drugs. Clinically, the particle size of a drug can affect its release from dosage forms that are administered orally, parenterally, rectally and topically. The successful formulation of suspensions, emulsions and tablets; both physical stability and pharmacologic response also depends on the particle size achieved in the product.

The particle size distribution of active ingredients and excipients is an important physical characteristic of the materials used to create pharmaceutical products. The size, distribution and shape of the particles can affect bulk properties, product performance, processability, stability and appearance of the end product.

The link between particle size and product performance is well documented with regards to dissolution, absorption rates and content uniformity. Reducing particle size can aid the formulation of NCE’s with poor water solubility. Proper matching of active ingredient and excipient particle size is important for several process steps. Particle size analysis is an integral component of the effort to formulate and manufacture many pharmaceutical dosage forms. HORIBA Instruments can provide both the analytical tools and technical support required to help pharmaceutical companies characterize their particulate systems with confidence.


DISCUSSION:
Even though the experiment above was successful but the results are not very accurate due to some errors that occur throughout the experiment. As we can see, the total mass of lactose and MCC before and after sieving is not the same. This is due to some of the particles being stuck in the sieve and also the sides of the container. Next, when obtaining the lactose and MCC from the sieves, some of the particles have dropped to the surroundings and hence lost in the process. Therefore, an inaccurate value of mass for the particle size ranges are obtained. The analytical balance that is not calibrated well is also one of the causes for inaccurate readings.

CONCLUSION

 In this experiment,particle size distribution of powder and the size of solid particleof  lactose and microcrystalline cellulose (MCC) by sieve nest successfully determined.The size of particle also got to be determined.

REFERENCE:

1. cma.tcd.ie/misc/particle.ppt
2. Martin's Physical Pharmacy and Pharmaceutics 6th Edition.
3. http://www.horiba.com/scientific/products/particle-characterization/applications/pharmaceuticals/