PRACTICAL 4 (Part B): Particle size and shape analysis using microscope

Title : Particle size and shape analysis using microscope

Objective : To determine the particle size and shape analysis on different types of sands and powder such as MMC and lactose

Apparatus : microscope, slide, cover slip, spatula

Chemicals : sands (150µ, 355µ, 500µ, 850µ, mixed), MMC, lactose

Introduction :

Microscopy is a method that allows the individual particles to be observed and measured. A digital camera with a fixed magnification lens is used to take a picture of a sparse layer of representative particles distributed on the microscope slide. An image analysis program is used to obtain measurements by analysing the number and shade of individual pixels. Only a small quantities of representative particles are needed in the analysis. For this experiment, we will be using a microscope to analyse 5 different types of sands (150µ, 355µ, 500µ, 850µ and mixed)  and powders (MMC and lactose) with particular emphasize on the size and shape of the particles. The particles observed microscopically are being sketch and the general shape for the particular material are being determined. Magnification used should be the same for sketching the particles.

Experimental procedure :

1. A microscope was used to analyse 5 different types of sands which are 850mic, 500mic, 355mic, 150mic, various sizes, and powders (MCC and lactose).

2. The particles observed microscopically were then sketched and the general shapes for that particular material were determined.

3. The magnification used in sketching the materials was fixed.

Result :

Discussion :

            In pharmaceuticals, particle size analysis is important to ensure the efficacy of drugs in the body. Particle size influences the rate of dissolution of drug in which, smaller particle has a larger surface area that dissolves rapidly than the larger one. Other than that, particle size and shape affects the flow properties of powders. Basically, coarse, roughly spherical particles flow easier than elongated particles. Particle size also affects the stability of dispersion such as suspension and emulsions.

            There are many ways to determine the size and shape of particle and one of the ways is by using microscope. In this experiment, light microscope is used to analyse the size and shape of sands. The sands observed include 850µ, 500µ, 355µ, 150µ and various size. Other than sand, two powders was also being analysed and they are lactose and microcrystalline cellulose (MCC).

            Based on the result obtained from the experiment, we observed that the sands have different sizes and irregular shape between each other. If compared to the powders, powders are smaller in size but their shapes are also irregular. Sand 150 mic is has the smallest size among all sands while between both powders, MCC is smaller than lactose.

            Precaution steps must be taken while conducting the experiment such as wearing goggles to avoid any small particles from the experiment from entering the eye and wearing gloves to prevent any particles from having direct contact with the skin. Besides, the sands and powders must be placed on the slide as a thin one layer so that it will be easier to be observed under the microscope. The experiment should be conducted carefully to prevent the materials from spilling out anywhere and being wasted.

Questions :

1. Explain in brief the various statistical methods that you can use to measure the diameter of a particle.

There are two types of statistical methods that can be used to measure the diameter of a particle such as the Martin’s and Feret’s diameter and the histogram. Martin’s diameter is defined as the averaged cord length of a particle which equally divides the projected area. Feret’s diameter is averaged distance between pairs of parallel tangents to the projected outline of the particle. The projected area diameter is the diameter of a sphere having the same projected area as the particle. The histogram shows the distribution of sizes of the particle in different size range.

Martin’s and Feret’s diameter of a particle depend on the orientation of particle which is made by the measurement. A large number of randomly sampled particles is needed to obtain a significant measurement at a fixed orientation. Usually Martin's and Feret's diameter method is used in optical and electron microscope. The histogram method will be used when most powders contain particle of different diameters. The histogram method is being used as it show the distribution of size particles in three types such as normal distribution, positive skewed distribution and bimodal distribution.

2. State the best statistical method for each of the samples that you have analysed.

The most suitable statistical method for the samples that we had analysed is Martin’s and Feret’s diameter. This is because we are observing the particle under a microscope during the experiment. Thus, this is the most suitable method to measure the diameter of the particle.

Conclusion :

Different types of sands and powders can be analysed through a light microscope. Each of the particles is different in shape and size. Overall we are able to determine the shape of the particles and we can conclude that they are asymmetrical and irregular. This shows that the granulation is important to ensure that the flow ability of drug can be achieved. 

References :

1.      Keping, Sun. Recent Developments in Applied Electrostatics Proceedings of the Fifth International Conference on Applied Electrostatics, November 2-5, 2004, Shanghai, China. S.l.: Elsevier Science, 2005. Print.

2.      Reider, Ralf, and I-Wei Chen. Ceramics Science and Technology: Vol. 3. Weinheim: Wiley-VCH Verlag GmbH, 2011. Print.

3.      Augsburger, Larry L. Pharmaceutical Dosage Forms Tablets. 3.rd ed. New York: Informa Healthcare, 2008. Print.

4.      Michael E. Aulton, Aulton’s Pharmaceutics The Design And Manufacture of Medicine, 3rd Edition (2007), Churchill Livingstone Elsevier (page 122-134) 

5.       A. T. Florence and D. Attwood, Physicochemical Principals of Pharmacy, 2nd Edition, The Macmillan Press Ltd.

PRACTICAL 4 (Part A): Sieving

Title: Sieving

Objectives:

1. To determine the size and size distribution of a particular powder.

2. To classify and differentiate the powder based on its diameter.

Date of experiment: 16^th November 2015

Introduction

            Sieving is one of the oldest particle size analysis methods. This sieving method is used to classify powders and granules by particle size distribution. The sieves are arranged in decreasing order of the sieve number. The particle size that passes through the sieve also decreases from top to bottom. In this experiment, 100g of microcrystalline cellulose (MCC) is weighed and placed on the uppermost sieve. The sieves are shaken rigorously on a mechanical shaker for a certain period. The MCC powder collected at each sieve is weighed and recorded.

Apparatus:

1.      Mechanical sieve

2.      Sieve nests

3.      Large weighing boats

4.      Spatula

5.      Electronic balance

Materials:

1.      Microcrystalline cellulose (MCC)

2.      Lactose

Experimental Procedure:

1.      100g MCC and lactose were weighed.

2.      The sieve nest was prepared in descending order (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.      Upon completion, the powder at every sieve was collected and the weight is measured.

5.      The particle size distribution of MCC and lactose were plotted in the form of a histogram.

Results :

Lactose
Diameter of sieve nest (µm)	<150	150-212	213-299	300-354	355-425	>425
Weight (g)	0.3021	8.1646	6.46963	3.2764	48.3759	33.3162

MCC
Diameter of sieve nest (µm)	<53	53-149	150-199	200-299	300-500	500
Weight (g)	17.5855	76.8885	3.3547	1.8236	0.2216	0.1261

Discussion :

            Particle size analysis is a particle size measurement, using variety of name of the technical procedure or laboratory techniques which determine the range of particle size or the average particle size of the size in the powder or liquid form. In this experiment, the sieve method is used.  There are two types of sieve analysis, dry sieving and wet sieving. Dry sieving can used in cement industry, fertilizer industry and building construction while wet sieving is special used in ceramic industry, pharmaceutical industry and cosmetic industry. Sieve is a device for separating particles of different sizes. Coarse particles which are in different particle size are separated by passing through the sieve nest with different diameters which arrange from largest diameter to the smallest diameter.

            There are some sources of errors occurred during the experiment. First and foremost, apparatus used in the experiment contains impurities. Since the sieve nest is repeated used by several groups in the experiment, the sieve nest is not clean and contain impurities. This alter the final results which is the average particle size of lactose and MCC.  Therefore, we must wash and dry the sieve nest before use in other to obtain more accurate result. Next, the weight of lactose and MCC are different before and after the experiment. This is due to the dispersed and spilled of the tiny size and light powder to the surrounding. The precaution of this error is do the experiment in a closed area and repeat the experiment to get the average result.

Questions:

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

Between 355-425µm lactose and 54-149µm MCC.

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

Microscope method-an excellent technique because we can look at the shape and size of the particles directly.

Coulter counter-it uses electrical stream sensing zone method where it measures the material that can be suspended in an electrolyte.

Laser light scattering method-it uses laser diffraction which results from interaction of light with particles.

Dynamic light scattering method-Brownian motion principle is used to measure particle size and the photon correlation spectroscopy (PCS) analyses the changing patterns of laser light scattered.

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

Particle size is important in pharmaceutical formulation because it has an effect on the absorption of drugs. Particle size also affects the disintegration time of the tablets. Besides, the particle size of a pharmaceutical semi-solid dosage influences the efficacy, safety and performance of the dosage form. It affects the penetration of the drug into the skin and also the flux rate of the active ingredient. 

Conclusion:

Sieving is one the methods that can be used to separate solids such as powders of different sizes. This experiment clearly shows that methylcellulose crystalline (MCC) and lactose have different particle size distribution and can be differentiated according to sizes by using a mechanical shaker of different apertures at each layer to sieve the powders. From the results, it can be concluded that the particle size distribution of lactose is larger than that of MCC because most of the lactose particles are accumulated at the sieve nest of diameter 355-425µm, while most of the MCC particles are accumulated at the sieve nest of diameter 54-149µm.

References:

http://www.pharmainfo.net/tegkmurthy/blog/influence-particle-size

http://www.pharmacopeia.cn/v29240/usp29nf24s0_c786.html

PRACTICAL 3 (Part B): Mutual solubility curve for phenol and water

Title : Phase diagram (Part B): Mutual solubility curve for phenol and water 

Date of experiment : 2 November 2015

Objectives :

1) To study the relationship between solubility of mixture of water with difference percentage of phenol composition and temperature.

2) To determine and construct the mutual solubility curve for phenol and water.

3) To obtain the Critical Solution Temperature (CST) from the mutual solubility curve.

Introduction :

            Some liquids are miscible with each other in all proportions to form homogenous solution. However, some other liquids have miscibility in limited proportions in other liquids. For example, ethanol and water are miscible with each other in all proportions while etherwater and phenol-water are liquids that partially miscible yielding either one or two liquid phase, depending on the condition.

            Generally, the temperature of the system can influence the miscibility of liquids. When the temperature increases, the mutual solubility of partially miscible liquid will also increases until it reaches the consolute point which also known as critical solution temperature. This temperature is the critical temperature above which the components of a mixture are completely miscible in all proportions which can be obtain from the mutual solubility curve. It is difficult to determine the upper and lower critical solution temperature except for nicotine and water.

            The mutual solubility curve for phenol and water can be determined by analytical and synthetic method. At any temperature below the critical solution temperature, the composition for two layers of liquids 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 liquids in general is extremely influenced by the presence of third component. The mutual solubility curve for phenol and water can be determined by analytical method and synthetic method.

Apparatus :

Test tube

Test tube rack

Thermometer

Beaker 20mL

Parafilm

Aluminiun fold

Water bath

Measuring cylinder 10mL or 20mL

Chemical :

Phenol

Distilled water

Experimental procedure :

1) 5 set of the phenol with concentration scale 8% to 80% are determined. The volume of phenol and distilled water used are calculated by using the total volume of 20mL.

2)  5 test tubes are prepared and placed on the test tube rack.

3) The phenol and distilled water are mixed with different concentrations and they are stirred by using the thermometer. Then, the opener of test tubes are quickly sealed with parafilm and aluminium fold.

4) The test tube are placed in the water bath and the temperature at which the liquid become 2 clear layers are recorded.

5) The test tubes are removed and cooled down. The temperature at which the liquid become cloudy are recorded.

6) The average temperature for each test tubes is calculated.

7) The graph of average temperature against percentage of phenol is plotted. The critical solution temperature is determined from the graph.

Result :

Set	Percentage of phenol (%)	Percentage of water (%)	Temperature single-phase (0C)	Temperature double-phase (0C)	Average temperature (0C)
1	8	92	29.0	24.0	26.5
2	20	80	60.0	56.0	58.0
3	40	60	68.0	56.0	62.0
4	60	40	45.0	39.0	42.0
5	80	20	26.0	24.0	25.0

Discussion :

            Phase rule is the principle that in any system in equilibrium the number of degree of freedom is equal to the number of components less than the number of phases plus two. It is a useful device for relating the effect of the least number of independent variables, for instance ,concentration, pressure and temperature upon the solid, liquid and gases that can exist in equilibrium system containing a given number of components. The phase rule can be express as F=C-P+2 where F is the number of degree of freedom, C is the number of component and P is the number of phases present. F, the number of degree of freedom is the least number of intensive variables that must be fixed to describe the system completely. C, the number of component is the smallest number of constituents by which the composition of each phase in the system at equilibrium can be expressed in the form of a chemical formula or equation .P, the number of phases present is number of homogenous, physically distinct portion of a system that is separated from other portions of the system by bounding surface.

In this experiment, we used two component which is water and phenol .The miscibility of phenol and water depends on the condition of temperature and also the percentage of the composition of phenol within the mixture of phenol and water. When phenol and water are miscible with each other, the degree of freedom, F= 2-1+2=3. As the pressure is fixed as 1 atp, the degree of Freedom will change to 2, which the variable is temperature and percentage of composition of phenol within the mixture of water and phenol. 

After the experiment was carried out, graph of average temperature against percentage of phenol composition is plotted. The ‘n’ shaped like curve graph is obtained which is mutual solubility curve. When the percentage of phenol composition less than 8%, the phenol and water and are completely miscible with each other to form water. When the percentage of phenol composition more than 80 %, the phenol and water will also completely miscible with each other to form phenol. Both situation exist as only 1 phase system. As the percentage of phenol composition  beyond 8%, the mixture exist as a two phase , at first , it exist as a water-rich phase , however , as the percentage of  phenol composition increase , the water- rich phase decreased gradually and changed to phenol-phase until beyond 80% . Both phenol and water is completely miscible with each other, exist as only 1 phase. Besides, the ‘n’ shaped curved shows the limit of the temperature and concentration within which the two liquid phase of phenol and water exist in equilibrium. The region outside the cure exist as a 1 liquid phase region while the region within the curve containing the system exist as a 2 liquid phase. The critical solution temperature is obtained by the maximum point of the ‘n’ shaped curve. This is known as the temperature of the maximum temperature at which two phase region exists and separated.

            From the result that obtained from the experiment, some of the points in the graph are slightly deviated from the actual mutual solubility curve. Moreover, the critical solution temperature obtained from the experiment is 64 ⁰C, while the actual reading is 66.8 ⁰C.This is due to some errors are occurred during the experiment was carried out .First and foremost, the opener of the test tube is not seal tightly by parafilm. This will lead to the evaporation of phenol once phenol is mixed with the water. The evaporated phenol can affect the actual composition of phenol within the mixture, consequently, the accuracy of the result is also affected. Moreover, the actual reading of the temperature changed of the mixture right after out of the water bath and cooling down is not recorded correctly due to the temperature increase and drop rapidly. Hence, to avoid this error, faster reaction to take record the temperature at which solution turn clearly .Moreover, the reading of the temperature after cooling down must be recorded immediately. This two precaution step can help to get the more accurate average temperature.  The desired volume of the solution of the mixture between water and phenol is inaccurate due to the use of wrong apparatus which is measuring cylinder.  Burette is the apparatus that supposed to use to get the actual desired volume of the both solutions in the mixture. 

Question :

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

            

The addition of foreign substances can change the binary system to produce ternary system. Binary system is the closed system that contains two components while ternary system is the closed system that contains three components. The addition of the foreign substances can give effect toward the critical solution temperature and the phase separation of the mixture. If the foreign substance is soluble in only one of the two components or the solubility of foreign substance is very different from the two components, the mutual solubility of the mixture will decrease and causes the critical solution temperature become lower. For example, the addition of foreign substances like salts can reduce the miscibility of water and phenol. This will cause the water molecules to hydrate the salt ions, reducing the tendency of water molecules to solvate the phenol. On the other hand, if the foreign substance is soluble in both components, the mutual solubility of mixture will increase and the critical solution temperature will become higher. For instance, when succinic acid is added to phenol-water mixture, this will cause the mixture become one phase. The addition of foreign substances is important in preparation of pharmaceutical solution. By knowing the properties of the drug and the mutual solubility between foreign substances with drug, the best solvent of the drug can be determined.

Conclusion :

The critical solution temperature in the experiment is 64⁰C. The increase of temperature can increase the miscibility of the mixture. When the phenol-water mixture reached the critical solution temperature, all combination of phenol and water above this temperature are completely miscible and yield one-phase liquid system.

References :

1) Physicochemical Principles of Pharmacy (4^th) edition by Alexander T Florence and David    Attwood

2)  Sinko, Patrick J., Martin’s Physical Pharmacy and Pharmaceutical Sciences, 5th ed., Lippincott Williams & Wilkins, 2005. page 51.

3)https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=number%20of%20degree%20of%20freedom%20definition