Practical 4a :Particle Size and Shape Analysis Using Microscope

Title: Particle size and shape analysis using microscope

Date: 22th November 2016

Objective: To investigate and analyse the size and general shape of particles of different types of sands and powders under microscope.      

Introduction:

            Particle size and shape are important in achieving optimum production of efficacious medicine. Bioavailability is often directly related to particle size because it controls solubility characteristics of the drugs. Dissolution rate is directly proportional to particle surface area. The smaller the particle size of the drugs, the larger its surface area is. So, a smaller particle size promotes faster drug dissolution. Particle size distribution is also relevant as a narrow distribution produces more uniform dissolution. Formulations with even a small number of relatively large particles may take some time to dissolve completely, but this may be the design intent. Hence, analysis of particle size and shape is always important before a medicine reach the consumer.

            In order to interpret and analyse the particle size and shape of the solid drugs, a few method can be used. One of the common method that is use is microscopic analysis.

Apparatus:

Electron microscope

100ml beaker

Spatula

Glass slide

Material:

5 different types of sand

MCC powder

Lactose powder

Procedure:

1)A microscope was set up.

2)Sand with particle size of  150mic, 355mic, 500mic, 850mic and various sizes , lactose powder and MCC were place in different beaker with label A, B,C,D,E, lactose and MCC respectively using a spatula .

3)Sand from beaker A was scattered on a glass slide.

4)The sand was observed under microscope using different magnification.

   

5)General shape of the sand was determined.

6)Step 3,4 and 5 were repeated using sand from beaker B,C, D, E, lactose and MCC.

Result:

                                                                        150mic(25x)

The particles size of the sand is very small, almost the same in size but different in shape. 

                                                                         355mic(4x)

The sand particles of  355 mic is bigger than that of 150 mic. The particles are irregular in shape.

                                                                            500(25x)

The sand particles are bigger than the sand of 150 mic and 500 mic stated above and similar in size. Their shapes are irregular but are generally of low sphericity and look angular.

                                                                          850(25x)

The sand particles is larger than the sand particles of 150micron, 355micron and 500micron and almost same in size. The particles shapes are irregular, but generally they are of very low sphericity.

                                                                   Various size(4x)

The shape of the sand particles is very irregular and different sizes of sand particles are observed. Some particles appear to the much bigger than all the 150mic, 355mic, 500mic, and 800mic sands observed before and some has approximately same size with them.

                                                                         MCC(4x)

Particles of MCC powders are almost the same size and shape as most of the particles give rice-shape appearance.

                                                                      Lactose (4x)

Lactose has the smallest particle size compared to all the samples above. The particles are of more constant shape as they are generally spherical. The particles are of almost the same size in the sample.

Discussion

In this experiment, different types of sands and powders which are lactose powders, MCC powders, 150micron sands, 355micron sands, 500micron sands, 850micron sands and sands of various sizes are examined using a light microscope. The particle size and shape are examined and analysed. From the observation, the general shape of sand particle is not uniform and varies distinctly from one and another. The shape of MCC and lactose is especially difficult to define due to the very small size of the powder particle.

From the observation of sand particle, due to the larger size the sand can be distributed evenly so each particle shape can be seen and observed clearly. On the whole, the sand particles are asymmetrical and sizes vary. On the other hand, the powder are fine, thus are distributed unevenly and single particle is difficult to obverse. On the whole, the particle are more uniform in shapes and sizes.

Besides, the particle size analysis can be done further by using various methods such as projected area diameter, projected perimeter diameter and better by using Feret’s diameter or Martin’s diameter, as these two methods consider the orientation of particles and, the particles can be examined individually. Feret’s diameter is the mean distance between two parallel tangents to the projected particle perimeter while Martin’s diameter is the mean chord length of the projected particle perimeter. Besides, electron microscope can be used to examine the orientation and shape of the image in three diminsional.

During the experiment, we have to make sure that the sample particles is well-spread throughout the slide and dispersed evenly under the microscope. It is to avoid the agglomeration formed and ensure the image of specimen we obtain is accurate and clear in term of their shape and size. We also are advised to wear goggles and mask to prevent the sand and powder gets into our eyes and to protect ourselves safety.

Question

1.      Describe the variety of statistical method used to measure diameter of particles.

Monosized particles consist of equivalent spheres with the same diameter. However, most powders contain particles with different diameters and size. First, projected area diameter is used to measure the equivalent area to that of projected image of the particle . Projected area is two-dimensional area measurement of a three-dimensional object by projecting its shape on to an arbitrary plane. Likewise, projected diameter is also used by which the circle having the same perimeter as the particle. However, the weakness is that these method do not take the orientation into consideration. Only two dimension of  particle in consideration is inaccurate for unsymmetrical particle.

Martin’s diameter is also used to determine the diameter of a particle. By using this method, the diameter of irregular shaped particles is measured. Martin’s diameter is the measured distance between opposite sides of a particle, and is measured transverse to the particle on a line that bisects the projected area. In other words, Martin’s diameter measures the chord of a particle and is useful for estimating the surface area of an irregular non-spherical particle.

Feret’s diameter also called the caliper diameter, is a measure of an object size along a specified direction.  It can be defined as the distance between the two parallel planes restricting the object perpendicular to that direction generally. The object size is measured with a caliper. This measure is used in the analysis of particle sizes and is applied to projections of a three-dimensional (3D) object on a 2D plane. Thus, it is also defined as the distance between two parallel tangential lines rather than planes.

Feret’s diameter and Martin’s diameter depend on both the orientation and the shape of the particle. These are statistical diameters which are averaged over many different orientations to produce a mean value for each particle diameter.

2.      The best method that should be used on this experiment.

Feret’s and Martin’s diameter will be the best method as these methods are averaged over many different orientations to produce a mean value for each particle diameter.

Conclusion

As a conclusion, each of the particles has different shape and size and they are irregular by using microscope to analyze. The size of the particle which is smallest is lactose powders, followed by MCC powders, 150micron sands, 355micron sands, 500micron sands, 850micron sands and sands of various sizes.

Reference

1) Physicochemical Principals of Pharmacy (2nd Edition) AT Florence and D.Attwood, The Macmillan Press Ltd.

2) https://en.wikipedia.org/wiki/Particle-size_distribution

3) http://158.110.32.35/CLASS/IMP-CHIM/PGSF21-42.pdf

Practical 3a : Mutual Solubility Curve for Phenol and Water

Title: Mutual Solubility Curve for Phenol and Water

Date: 7^th November 2016

Objectives:

1.      To determine the solubility of two partially liquids (phenol – water solution)

2.      To construct the mutual solubility curve and determine the relationship between the temperature and solubility of the liquids

3.      To determine the critical solution temperature

Introduction

Some liquid are completely immiscible (eg. Oil and water) while some are completely miscible in all proportions (eg. Ethanol and water) . However, many liquid mixtures fall between these two extremes. If you shake equal volumes of two of these liquids together, you often get two layers with unequal volumes. These liquids are “partially miscible”.

As the temperature rises, both liquids become more soluble in each other. They reach a mutual solubility temperature or critical solution temperature. Above that point, the mixture becomes homogeneous, where one layer will be formed. Below that point, the mixture separates into two layers.

Phenol is also soluble in water to some extent due to its ability to form hydrogen bonding with water molecules. Nevertheless, the large part of phenol molecule is phenyl group that is non-polar. Hence its solubility is limited in water. However the polarity of this part increases in phenoxide ion when the temperature is raised, and hence the liquids will be more soluble. 

At any temperature below the critical solution temperature, the composition for two layers of liquid in equilibrium state is constant and does not depend on the relative amount of these two phases. The mutual solubility for a pair of partially miscible liquid in general is extremely influenced by the presence of third component.

Apparatus

Boiling tube, Test tube, Measuring cylinder, 5ml pipette, 1ml pipette, Water bath, Thermometer

Materials

Distilled water, Phenol

Procedure

1.      Five boiling tube is prepared and labelled as A, B, C, D and E

2.      The boiling tubes are filled with different amount of water and phenol with the respective percentage.

a.       Boiling tube A with 8% of phenol

b.      Boiling tube B with 30% of phenol

c.       Boiling tube C with 50 % of phenol

d.      Boiling tube D with 70% of phenol

e.       Boiling tube E with 80% of phenol

          

3.      Heat the boiling tubes with water bath. The boiling tubes were swirled and shaken well.

4.      The tubes were observed and temperatures were recorded when the turbid becomes clear.

5.      The tubes were removed from the hot water and the temperature was allowed to reduce. As soon as the liquid becomes turbid and two separate layers were form, the temperature is recorded.

6.      Steps 1 – 4 are repeated.

7.      By using the temperature obtained, the average temperature for each tubes at which the two phases were no longer seen or at which two phases were exist were determined.

Result

SET	PERCENTAGE OF PHENOL (%)	PERCENTAGE OF WATER (%)	TEMPERATURE WHEN MIXTURE BECOME ONE LAYER (°C)	TEMPERATURE WHEN MIXTURE BECOME TWO LAYER (°C)	AVERAGE TEMPERATURE (°C)
1	8	92	65	X	65.0
2	30	70	74	72	73.0
3	50	50	77	75	76.0
4	70	30	71	68	69.5
5	80	20	X	X	X

  

GRAPH

Discussion

            Phase rule is a device that is used to relate the effect of the least number of independent variables upon various phases that can exist in an equilibrium system which have a given number of components. The phase rule can be expressed as F= C-P+2 where F is the number of degrees of freedom in the system, C is the number of components and P is the number of phases present. In this experiment, phenol and water is used as the components where phenol is partial miscible with water. When phenol is miscible with water at certain condition, the number of degrees of freedom in the system, F=2-1+2=3 . Since the pressure is fixed for this system which is the atmospheric pressure, F is reduced to 2. This means that we need to fix both temperature and concentration to define this system. When phenol is immiscible with water at certain condition, the number of degrees of freedom in the system ,F =2-2+2=2 . Since the pressure is also fixed for this system which is the atmospheric pressure,F is reduced to 1. This means that we only need to fix the temperature to define the system.

            After the experiment , a graph of temperature at complete miscibility versus phenol composition in different mixture is plotted. A n-shaped graph is obtained. This curve shows the limits of temperature and concentration within which phenol and water exist in equilibrium. The region outside the curve shows that phenol is miscible with water(1 liquid phase) while the region within the curve shows that phenol is immiscible with water(2 liquid phase).The maximum temperature at which the 2 liquid phase exist is called critical solution temperature. The critical solution temperature in this experiment is 76.2°c.

            The curve that is obtained from the experiment have some slight deviation compared to the actual mutual solubility curve. This occur because there are some error that have been done when conducting the experiment. Firstly, the tube are not tightly sealed. The tube together with the thermometer should be tightly sealed to prevent heat loss to the surrounding that will affect the reading of the temperature of the mixture. This can also prevent the evaporation of the phenol when it is heated. Besides that, the reading of the temperature should be taken immediately after the mixture become miscible or immiscible because the temperature of the mixture increase and drop rapidly. Lastly, parallax error might occur when taking the reading of the thermometer. The eyes of the observer should be perpendicular to the scale of the thermometer to prevent parallax error.

Questions

Explain the effect of adding foreign substances and show the importance of this effect in pharmacy.

ANS: The addition of foreign substances may affect the critical solution temperature. When the substances added dissolve in only one of the two liquid, the mutual solubility will decreased. The temperature at which the system become 1 liquid phase will increased if the system has upper critical solution temperature and temperature lowered  for system that has lower critical solution temperature. This concept is important in pharmacy as its help the pharmacist to select suitable solvent for a drug and help overcome problem arise during preparation of drugs.

Conclusion

Phenol and water are immiscible unless it meets certain temperature at particular concentration. As the concentration of phenol in the mixture increase, the temperature for the phenol to become miscible with water increase until it reach the critical solution temperature which is 76.2°c. After the critical solution temperature, the temperature of the mixture drops even though the concentration of the phenol increase.

References

1)Lecture note (Phase diagram 1)

2) College Practical Chemistry, by V K Ahluwalia, Sunita Dhingra (2005)

3) https://socratic.org/questions/what-is-mutual-solubility-temperature

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.