Practicle 4a: Sieving

Objectives

ü  To determine particle size distribution of lactose and microcrystalline (MCC).

ü  To identify the size of solid particle of lactose and microcrystalline (MCC).

Date of Experiment

22 November 2016

Introduction

A sieve is a tool for separating lumps from powdered material or grading particles or for characterizing the particle size distribution of a sample, basically using mesh or net. Agglomerates are usually broken down by sieves, and the particle size and size distribution of a particular powder is determined by sieve analysis. Sieve nest is used to assess the particle size and the size distribution of both lactose and microcrystalline cellulose (MCC) which are excipients that commonly used in tablet formulations.

Apparatus And Materials
Lactose
Microcrystalline cellulose (MCC)
Weighing machine
Stack of sieves
Mechanical sieve shaker

Procedure

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

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

3. Lactose is placed at the uppermost sieve. 

4. The sieving machine is run for 10 minutes(&20 minutes).

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

6.  Step 1-5 are repeated using MCC to replace lactose.

Results

Lactose 10 minutes

Sieve Diameter (µm)	Particle size (µm)	Mass of Lactose retained in the sieve (g)	Percentage of lactose  retained = (w sieve/w total) x 100% (%)	Cumulative percentage retained(%)	Percentage of lactose passing  = 100% -cumulative percentage retained(%)
500	355< x ≤ 500	26.2340	26.56	26.56	73.44
355	355 ≤ × <500	45.7467	46.31	72.87	27.13
300	300 ≤ × <355	8.6832	8.79	81.66	18.34
212	212 ≤ × <300	8.9177	9.03	90.69	9.31
200	200 ≤ ×< 212	0.0672	0.07	90.76	9.24
150	150 ≤ ×< 200	2.6130	2.65	93.41	6.59
45	45 ≤ ×< 150	6.2178	6.29	99.70	0.30

Lactose 20 minutes

Sieve Diameter (µm)	Particle size (µm)	Mass of Lactose retained in the sieve (g)	Percentage of lactose  retained = (w sieve/w total) x 100% (%)	Cumulative percentage retained(%)	Percentage of lactose passing  = 100% -cumulative percentage retained(%)
500	355< x ≤ 500	27.9594	28.071	28.071	71.929
355	355 ≤ × <500	47.1532	47.342	75.413	24.587
300	300 ≤ × <355	6.2833	6.308	81.721	18.279
212	212 ≤ × <300	2.5117	2.522	84.243	15.757
200	200 ≤ ×< 212	0.0088	0.008	84.251	15.749
150	150 ≤ ×< 200	0.0766	0.077	84.328	15.672
45	45 ≤ ×< 150	13.8096	13.865	98.193	1.807

MCC 10minutes

Sieve Diameter (µm)	Particle size (µm)	Mass of MCC retained in the sieve (g)	Percentage of MCC  retained = (w sieve/w total) x 100% (%)	Cumulative percentage retained(%)	Percentage of MCC passing  = 100% -cumulative percentage retained(%)
710	600< x ≤ 710	0.0036	0.005	0.005	99.995
600	600 ≤ × <710	0.0007	0.001	0.006	99.994
425	425 ≤ × <600	0.0485	0.075	0.081	99.919
300	300 ≤ × <425	0.1148	0.177	0.258	99.742
150	150 ≤ ×< 300	4.9990	7.706	7.964	92.036
53	53 ≤ ×< 150	50.6871	78.134	86.098	13.902
50	50 ≤ ×< 53	9.0179	13.902	100	0

MCC 20 minutes

Sieve Diameter (µm)	Particle size (µm)	Mass of MCC retained in the sieve (g)	Percentage of MCC  retained = (w sieve/w total) x 100% (%)	Cumulative percentage retained(%)	Percentage of MCC passing  = 100% -cumulative percentage retained(%)
710	600< x ≤ 710	3.0839	4.20	4.20	95.8
600	600 ≤ × <710	2.7706	3.77	7.97	92.03
425	425 ≤ × <600	3.1839	4.34	12.31	87.69
300	300 ≤ × <425	3.1520	4.29	16.60	83.40
150	150 ≤ ×< 300	6.9298	9.44	26.04	73.96
53	53 ≤ ×< 150	44.4114	60.48	86.50	13.5
50	50 ≤ ×< 53	9.9029	13.48	100	0

Discussion

A sieve analysis is a practice or procedure used to assess the particle size distribution of a granular material. The size distribution plays an important role to the way the material performs in use. A sieve analysis can be applied on various 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. Being such a simple technique of particle sizing, it is probably the most common.

Sieve nest was prepared in descending order, from the largest diameter to smallest. In this experiment, sieving process was started with 100 g of lactose or microcrystalline cellulose (MCC) placed on uppermost. 10(and 20minutes) minutes later, the procedures of removing the sieving nest and measuring the powder from each sieve are done. Measurement of particles size of lactose and MCC powder was according to the principle that the particles cannot pass through certain sieve sizes due to the greater particle size than the sieve diameter. 

In corresponding of the result above, the particle size of lactose(10minutes and 20minutes) is in between 355µm to 500µm as the highest amount of lactose powder is retained at the sieve with diameter of 355µm. The particle size of MCC(10minutes and 20minutes) is estimated between 53µm to 150µm as the highest amount of MCC powder is retained at the sieve with diameter 53µm. Hence, lactose has bigger and more uneven particle size compared to MCC.

There are a few errors made in the experiment. There is loss of weight of lactose and MCC powder after sieving. For instance, the initial weight of lactose before sieving is 100g, has reduced to 99.611g after sieving and the initial weight of MCC before sieving is 100g, has reduced to 98.7560g. Due to the nature of air which is very light and fluffy, it caused some particles to be shaken away into the air during the sieving process. Perhaps some of the particles still sticked to the sieve when we are removing the sieve. The result might be inaccurate as the vibration of the sieving nest is not significant or strong enough in sieving the particles through the sieve diameter. The sieving nest is not clean as itself is contaminated with other powder. This may affect the results.

In order to minimize these errors, close the sieving nest tightly with the lid on to avoid particles escaping from the sieving machine. Be alert to clean and dry the sieving nest before conducting the experiment to avoid getting  inaccurate results. Besides, calibrate the sieving vibrator machine before using it for the experiment as to provide an accurate results.

Conclusion
   Particle size distribution of lactose and microcrystalline (MCC) is determined.

   The size of solid particle of lactose and microcrystalline (MCC) is identified.

References

1.    http://www.uta.edu/ce/geotech/lab/Main/sieve/index.htm#sthash.cqWhTlZo.dpuf

2.    http://www.pharmamanufacturing.com/articles/2013/fundamentals-particle-size-analysis/

3.    Martin,A.N. 2006. Physical Pharmacy: Physical Chemistry Principles in Pharmaceutical Sciences. 5th Edition. Philadelphia: Lea & Febiger

Questions

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

Based on the result of experiment, the average particle size for both lactose and MCC ranges between 53µm to 150µm.

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

Methods that can be used to determine the particle size:

ü   microscope method

ü   coulter counter

ü  laser light scattering method

ü  dynamic light scattering method

ü  sedimentation method

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

Reaction rate of particles in adsorption, distribution, metabolism and elimination in the human body is influenced by particle size. Next, the size of particles can affect viscosity and flow, and increasing the polydispersity of particle sizes in a powder can improve its flow properties. Besides, it affects the behaviour of a formulation during processing and, ultimately, its content uniformity.  It also determine the particles appearance and texture in form of powder, tablets or capsules. Last but not least, the particles size also affects the distribution of the active ingredients in the formulation.