PRACTICAL 4 : Particle size And Shape Analysis Using Microscope

Title:
Particle size And Shape Analysis Using Microscope

Date
17 November 2014


Objective
  1. To analyse the general size and shape of particle under the light microscope.

   2.  To describe the distribution particle size and shape


Introduction

                The dimensions of particulate solids are important in achieving optimum production of efficacious medicines. When drug is synthesised and formulated, the particle size of drug and other powder is determined and this influences the subsequent physical performance of the medicine and the pharmacological of the drug. The particles which having small dimensions will tend to increase the rate of solution.

                 In order to obtain equivalent diameters with which to analyse and interpret the particle size of powder, it is necessary to carry out a size analysis using different methods. One of the method for particle analysis is using microscope.In this experiment.different type of sand and powders (MCC and lactose) is given to be observed microscopically and analysed such as the size and shape.

Apparatus

Light microscope
Glass slide
Weighing boat


Materials
- Five (5) different samples of sand  (850 mic, 500 mic, 355 mic, 150 mic and sand with various size) and powders (MCC and lactose).


Procedure

1. Microscope was set up.

2. 5 different types samples of sand were analysed by using microscope, by observing the size and shape of given particle.

3. The sample was put on the slide and was examined under microscope with  magnification of 4x10.

4.The shape and size of particles were sketched and analysed.

Result
150 Mic 
Magnification 4x10

 355 Mic
Magnification 4x10

 500 Mic
Magnification 4X10

 850 Mic
Magnification 4X10

 MCC
Magnification 4X10

Lactose
Magnification 4X10

Sand with various size
Magnification 4X10

Question

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

              There are some of the methods that can be use to determine the diameter of particle. One of the methods is projected area diameter which is measured based on the equivalent area to that of projected image of that particle. Projected area is two-dimensional area measurement of a three-dimensional object by projecting its shape on to an arbitrary plane. Another method is the projected perimeter diameter which is based on the circle having the same perimeter as the particle. Both of these methods are independent upon particle orientation. They only take into account of 2 dimensions of the particle, thus inaccurate for unsymmetrical particle.

               Feret’s and Martin’s diameter that considering the orientation and the shape of the particle are another methods to measure the diameter of certain particle. 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, which can be considered as the boundary separating equal particle area.

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

The best statistical method is by using Feret’s and Martin’s diameter.

Discussion

Each particles have been analysed and their structural have been observed.The general shape for each particles are very different from each other especially MCC  and lactose shape which are very small compared to the others.The total particles observed in the area are also vary with smaller particles are seen abundant in an area while the larger one are little.In sand with various size,the particles observed contain small and medium to big molecule.

Conclusion

Mcc and lactose have smaller particle due to the physical of the component in fine powder.Mcc shape was smooth and different lactose which is a dot-like shape. While the rest can be observed with larger particles according to their size.

References

1.http://www.horiba.com/fileadmin/uploads/Scientific/Documents/PSA/PSA_Guidebook.pdf

2.Michael E.Aulton, 2007, Aulton's Pharmaceutics The Design And Manufacture Of    Medicines, Third Edition, Churchill Livingstone Elsevier (page 122-134)

3.http://www.surfaceanalysis.ru/surface/categors/1f/74/content_128015234686.pdf

PRACTICAL 4 : SIEVING

Title  : Sieving

Date : 17 November 2014

Objective 
To determine the lactose and Microcrystalline cellulose ( MCC ) particle size distribution  by using sieve nest.

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. In its most common form it consists of a woven wire screen, with square apertures, rigidly mounted in a shallow cylindrical metal frame. For coarse sieving a perforated plate screen with square or round holes may be used in place of wire mesh. Square hole perforated plate sieves range down to 4mm and round hole sieves down to 1mm aperture. In this practical we are given a common excipient used in tablet formulation which is lactose.We are required to used the sieve nest to determine the particle size and the size distribution of lactose.

     

               Nevertheless, ‘micro’ sieving can be carried out down to 5 microns using special techniques. Particle size, as measured by test sieving, may be specified simply by quoting two sieve sizes, one through which the particles have passed, and the other on which they are retained. However, the most frequent use of test sieving is for measuring the size spread, i.e., the particle size distribution. Test sieving is not the only method available for particle size analysis, but it is certainly the most widely used and probably the most important. The materials which are tested in this experiment are lactose and microcrystalline cellulose.

Apparatus
 
1.sieve metal

2.weighing scale

Material 

Lactose

 

Microcrystalline cellulose ( MCC )

Experimental Procedure

1. 100g of lactose was weighed

2. A 'sieve nest' was prepared in ascending order and assigned appropriate sieve size

3. The lactose powder was put into the sieve.

4. Then, lactose powder was sieved for 20 minutes.

5. The results obtained was recorded and a histogram on powder particle size distribution was built.

6. The process was repeated with MCC.



Result

                                 



Microcrystalline Cellulose ( MCC ) Particle Size     Distribution

         



                      Lactose Particle Size Distribution            

             


Questions

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

 The overall particle size for both lactose and MCC is between 53 µm  and 150 µm.

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

      (a)Microscopy

       There are two types of microscopy which are optical microscopy (1-150µm) and electron

microscopy (0.001µ-). Microscopy is being considered as an absolute measurement of particle

size because it able to examine each particle individually. It can distinguish aggregates from

single particles. When coupled to image analysis computers each field can be examined, and a

distribution obtained.

     (b)  Sedimentation techniques

This method depends on the fact that the terminal velocity of a particle in a fluid increases with size. The particle size distribution of fine powder can be determined by examining a sedimenting  suspension of the powder.

    (c)  Electrical sensing zone method – Coulter Counter

Instrument measures particle volume which can be expressed as dv : the diameter of a sphere

that has the same volume as the particle. The number and size of particles suspended in an

electrolyte is determined by causing them to pass through an orifice an either side of which is

immersed an electrode. The changes in electric impedance (resistance) as particles pass through

the orifice generate voltage pulses whose amplitude are proportional to the volumes of the

particles.

  (d)  Optical sensing zone method

  (e)  Laser light scattering techniques

For laser diffraction, particles pass through a laser beam and the light scattered by them is

collected over a range of angles in the forward direction. The angles of diffraction are, in the

simplest case inversely related to the particle size.The particles pass through an expanded and

collimated laser beam in front of a lens in whose focal plane is positioned a photosensitive detector

consisting of a series of concentric rings.Distribution of scattered intensity is analysed by

computer to yield the particle size distribution. For Photon Correlation Spectroscopy, the rate of

change of these light fluctuations is used to determine the size distribution of the particles

scattering light.

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

For solid or suspension delivery systems, bioavailability is often directly related to particle size because it controls dissolution/solubility characteristics. Dissolution rate is directly proportional to particle surface area (Noyes-Whitney equation), so a finer 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.For suspensions, stability is an important issue because if the active ingredient settles there is a greater chance of non-uniform delivery. Stokes' law relates settling velocity to the physical characteristics of the fluid and the size of particles in the suspension. The relationship here is a strong one: velocity correlates with the square of particle diameter. For suspension stability, a very low settling velocity is preferable and is more easily achieved with finer particles. Perhaps less obviously, particle size may also affect a formulation's behaviour during processing and, ultimately, its content uniformity, which is critical.

Discussion

                   In this experiment, lactose and microcrystalline cellulose (MCC) were being observed for their particle size distribution. The method used was sieving method. It is also known as sieve analysis. Sieve analysis involves a nested column of sieves with wire mesh cloth (screen). See the separate Mesh (scale) page for details of sieve sizing. The sieve that has larger apertures was placed on top of the ones that having smaller apertures. This means, the sieve that have diameter of aperture of 425 µm will be placed at the top followed by 300 µm, 200 µm, 150 µm, and 53 µm. The column is typically placed in a mechanical shaker. The shaker shakes the column, usually for some fixed amount of time. After the shaking is complete the material on each sieve is weighed. The weight of the sample of each sieve is then divided by the total weight to give a percentage retained on each sieve.

                  From this experiment it shows that most particles size of lactose are in the range of 53 - 150µm (63.13 %) followed by range of 150 – 200µm (30.79 %) and 53 µm ( 3.65 %)respectively. While as for MCC, most particles size are in the range of 53 – 150 µm( 88.41 %) followed by less than 53 µm (6.50 %) and a range of 150 – 200µm (3.45 %).

                 For the particles cannot pass a certain sieve, it is because the particles are bigger than the aperture of the sieve. By this, we can deduce that most particles of MCC were finer than those of lactose.

                  At the end of the experiment, lactose and MCC in each sieve were collected back and were weighed. The final total weight of the lactose ( 98.17 g ) and MCC ( 99.55 g ) was not equal to the initial sample weight of 100g. The particles might loss to the environment ( by air movement/ wind ) during handling of the samples. During transferring of the samples from place to place we also not managed to cover the sample completely. Furthermore, the finer particles are prone to adhere or attach to the sieve nest. Some particles will also be escape from the sieving machine when the machine is operating. Thus, we have to make sure the sieving column was closed properly with the lid and clamped tightly to prevent the particles escaped from the sieving machine. We also need to make sure the sieving nest is clean and dry before conducting the experiment to obtain accurate results. However, the weight loss is very minute and negligible.

Conclusion

Most particles size of lactose are in the range of 53 - 150µm (63.13 %) followed by range of 150 – 200µm (30.79 %) and 53 µm ( 3.65 %)respectively. While as for MCC, most particles size are in the range of 53 - 150µm( 88.41 %) followed by less than 53 µm (6.50 %) and a range of 150 – 200µm (3.45 %). The overall particle size of MCC is smaller than lactose.

References

Jillavenkatesa A, Dapkunas S J, Lin-Sien Lum, Particle Size Characterization, NIST Special Publication , 2001


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


Paul Kippax, Particle size analysis, Pharmaceutical Technology Europe, 2009 from http://www.pharmtech.com/pharmtech/Analytical/Particle-size-analysis/ArticleStandard/Article/detail/588633

From http://www.horiba.com/scientific/products/particle-characterization/applications/pharmaceuticals/

Practical 3: Phase Diagrams (Part A) ; Determination of Phase Diagram for Ethanol/ Toluene/ Water System Theory ( 3 Components System )

Title :
Determination of Phase Diagram for Ethanol/ Toluene/ Water System Theory(Three Component System)

Date

3 November 2014

Objectives

1.Determination of the solubility limits in a ternary system of water and two other liquids (ethanol and toluene), one of which is completely miscible (ethanol) and the other is partly miscible with water (toluene)

2.Construction of the solubility curve of the system being studied on triangular diagram.

Introduction

              The making of pharmaceutical formulation often involve the mixing of multiple component together to achieve homogenous form.This is usually possible by knowing exact ratio of each component that needs to be mixed with taking consideration of temperature.This practical use three component of concern which were Ethanol,Water and Toluene.Water and Toluene are practically insoluble,as the mixing of the three component progress,the three component can reach homogenous state at equilibrium if such right component proportion were used.

          To present a three component system,ternary diagram is needed. Each side of a triangular diagram correspond one of the three component in the system and can be divided into part to produce equilateral grids as shown above. Thus any point in the diagram will show the amount of all three components while a point on the sides will show amount of any two components with each apex represent an amount of 100% of any one of the three components. 

         Following the basis of describing the effect of intensive variable to various phase in a system at equilibrium, which is the phase rule, it is determine that this system have 4 degrees of freedom. The four degrees of freedom are - temperature, pressure, and any two from the three component concentration. 

F = C – P + 2

F = 3 – 1 + 2

F = 4

Apparatus and Materials

1.Eight 100cm³ conical flask

2.Burette

3.Toluene

4.Ethanol

5.Distilled water

Procedure

1.Eight, 20 ml solution of toluene and ethanol were prepared in eight different 100cm³ conical flasks. Each flash were filled so that it contain 10%, 25%, 35%, 50%, 65%, 75%, 90% and 95% of ethanol with the rest was toluene.

2.The conical flask were labelled A, B, C, D, E, F, G and H respectively. Measuring these component were done by using a burette to make sure accuracy.

3.Each flask were titrated with burette filled with water and stopped when the solution in the flask turn cloudiness.The amount of water used in the titration was calculated and ratio of each component was calculated and tabulated in the figure below.

Result

Questions

Does the mixture containing 70% ethanol, 20% water and 10% toluene (volume) appear clear or does it form two layer?

The mixture will appear as clear solution.

What will happen if you dilute 1 part of the mixture with 4 parts of

            (a) Water

                  Two phases will be observed.

            (b) Toluene

                  Two phases will be observed.

            (c) Ethanol

                 One phase will be observed.

Discussion

           

                

                Each apex on the triangle representing the ternary system represents 100% of the component at that apex. The side of the triangle, directly opposite the apex, represents 0% of the apex component. Compositions of points which lie along the outside edge of the triangle are simply a mixture of the two components at each end of the tie line, with 0% of the third component.  In this experiment, A represents ethanol, B represents toluene while C represents water. The three lines joining the corner points represent two-component mixtures of the three possible combinations of A, B and C. Thus the lines AB, BC and CA are used for two-component mixtures of A and B, B and C, and C and A, respectively.

                         In this experiment, the system contains 3 components which are ethanol, toluene and water but only one phase. Thus, according to Gibbs’ phase rule F = 3-1+2 =4. 4 degrees of freedom included temperature, pressure, and the concentrations of two of the three components are required. Only concentrations of two components are required because concentration of the third component can be obtained by further calculation. 

This experiment was conducted under constant temperature and pressure.

                    From the data of the experiment, the plotted graph inside the triangular diagram formed a binomial curve. The region bounded by the curve shows the present of two liquid phases so the mixture is cloudy. The cloudy solutions formed indicates the phase separation, this is due to the insufficient amount of ethanol to produce a homogenous mixture. When the amount of ethanol is high, it will acts as surfactant which allow the two liquid phases become single liquid phase. Meanwhile, the single liquid phase of homogenous solution was shown at the region above the curve. We can conclude that ethanol helps to increase the miscibility of the two other components. 

                   There are several errors we had done during the experiment. Firstly, we poured and left the ethanol and toluene in the conical flask for a long time. Since ethanol and toluene are volatile liquids, their volume may be less than the actual one as some of them already evaporates. Therefore, the result was affected. Besides, parallax error may occur due to our eyes level was not perpendicular to the reading scale while measuring the volume of water in the burette. Furthermore, the room temperature in the laboratory may not constant thus affected the result obtained at the end of the experiment. Moreover, a random error occurred due to different person doing the observation. This is because different degree of cloudiness was achieved and the volume of water added obtained was inaccurate. 

                     To get an accurate result, there are some precaution steps that need to be taken. Firstly, the mixture of toluene and ethanol should be titrated immediately to prevent vapourisation or it should be sealed since both toluene and ethanol are volatile liquid. We must ensure that the eye is placed perpendicularly to the meniscus of the liquids to avoid parallax error. In addition, the temperature of the surrounding must be fixed and constant when carry out the experiment. One more important precaution step is only one observer is allowed to do the titration to make sure that the degree of cloudiness is same. Therefore, a more accurate result can be obtained.

                   

Conclusion

                      

             Phase diagrams are graphical representations of the liquid, vapour, and solid phases that co-exist at various ranges of temperature and pressure within a reservoir. Ternary phase diagrams represent the phase behaviour of mixtures containing three components in a triangular diagram. This experiment of ternary system involve three different liquids which are ethanol, toluene, and water and is represented using a triangle. From the experiment, as the number of volume of ethanol by percentage increase and number of volume of toluene by percentage decrease, the volume of water will increase. The two phase system was established once the cloudiness was observed.  Water and toluene form a two-phase system due to they are only slightly miscible. However, ethanol is completely miscible with both toluene and water. 

Reference

1.http://petrowiki.org/Ternary_phase_diagrams

2.http://www.brocku.ca/earthsciences/people/gfinn/petrology/ternary3.htm

3.http://gibbs.uio.no/phase_rule.html