Polarized Microscope Lab Report

TITLE :

Examination of Pharmaceutical Formulations Using A Polarised Microscope

OBJECTIVES :

1.      To study the used of polarized microscope.

2.      To measure the diameter of particle or droplet under the polarized microscope.

3.      To examined the pharmaceutical formulations using a polarized microscope.

INTRODUCTION :

The optical microscope is used extensively in pharmaceutical development with the primary application being solid-state analysis. The applications range from simple images of drug substance to illustrate particle size and shape to full optical crystallography. The range of utility of the microscope is considerably extended by the use of polarized light which allows us to obtain crystallographic data on small individual crystals.

Polarized light microscopy provides us a unique window into the internal structure of crystals and at the same time is aesthetically pleasing due to the colors and shapes of the crystals. The use of polarized light on the optical microscope allows us to determine the optical crystallographic properties of the crystal. Optical crystallography is related to but different from X-ray crystallography. Each technique provides unique information about the crystal structure and the combination of the two is powerful indeed. Based on optical crystallographic measurement it can yield as many as 20 different characteristics. The applications of this polarised microscope range from simple images of drug substance to illustrate particle size and shape to full optical crystallography.

So, in this experiment, we will use polarised microscope to observe. Gaviscon suspension and Scott’s emulsion cod liver oil. In which by using this polarised microscope we can observe crystal structure and properties of both substances.

MATERIALS :

·         Gaviscon suspension

·         Scott’s emulsion cod liver oil

·         Microscope slides and cover slips

·         Application sticks

·         Polariser

EXPERIMENTAL METHOD :

1)      On a clean and dry microscope slide, spread a thin layer of Gaviscon suspension (as thin as possible for best observation) using an application stick.

2)      Cover the sample gently with a coverslip.

3)      Observe and give a detail microscopic description of the suspension under bright light at x10.

4)      Under bright light, take snapshots and measure the average particle size. Take an average of at least 10 readings from different snapshots.

5)      Place the polarizer on top of the light source.

6)      Turn the polarizer until a crossed polar field was obtained. Observe and give a microscopic description of the suspension under the polarized light at x10.

7)      Repeat step 1-6 with Scott liver emulsion.

RESULTS :

1. Images of suspension and emulsion under bright field at Mag x10. (Print and label)

Suspension

Emulsion 

2. Images of suspension and emulsion under polarised field at Mag x10. (Print and label)

Suspension

Emulsion

3.  Microscopic description of suspension and emulsion under bright and polarized light.

Suspension under bright light is observed. There are many brown spots. But the figure is still doubted whether it is solid particles or dust. It is confirmed by using polarized light. A glitter-like spots are observed. The glitter-like spots are actually crystals as polarized microscope can detect crystallised particles.

Emulsion under bright light showed droplets of oil. Even it is observed under polarized light, the droplets still seen. Cause emulsion does not contain particles instead of droplet. So under polarized light the figure shown even darkness.

4. Measure the particle/droplet size (diameter). Take an average of at least 10 readings from different snapshots.

Reading (µm)	Gaviscon Suspension	Scott`s Emulsion
1	17.600	23.500
2	9.800	17.600
3	20.400	20.600
4	18.500	24.200
5	12.800	16.500
6	15.200	12.000
7	26.500	27.300
8	20.700	19.800
9	21.100	30.300
10	18.200	14.200
Average	18.090	20.600
Standard Deviation	4.684	5.790

DISCUSSION :

1.      Explain what is plane polarized light.

        Plane polarized light is the polarization state of the source of light used in polarizing microscope. Polarized light is light that vibrates in one single direction due to the passage through a polarizer. As the normal light vibrating in all direction perpendicular to the path of motion of the light ray while the polarized light vibrate in only one direction. Light is polarized when all of the light waves are vibrating in the same parallel direction. The polarizer use the principle of plane polarized light to differentiate the optical active substance and optical inactive substance.

                                                     

2.      Describe the differences between a normal and a polarized microscope.                   

	NORMAL MICROSCOPE	POLARIZED MICROSCOPE
Uses	View objects by illuminating normal light only.	Object can be viewed using both normal and polarized light.
Properties	Characterized by magnification and numerical aperture. Magnification ranges 5x to 100x while numerical aperture range 0.14 to 0.7	Numerical aperture range 0.9 to 1.35 and has same magnification as normal microscope.
Components	No polarizer and analyzer	Has polarizer and analyzer
Applications	Used to observe small microscopy objects and mostly used in biology field.	Used to determine optical crystallographic properties of crystals. Also used in geological sciences to study rocks and minerals, medicine, metallurgy and biology fields.

3.      From your results, explain how polarized light microscope is useful in examining pharmaceutical formulations.  

Polarized light microscope is useful in examining pharmaceutical formulations in which it can be used to determine mainly to differentiate between crystalline and non crystalline structure.  In this experiment, polarized light is used to differentiate the presence of liquid droplets in an emulsion and solid structure in a suspension. This is because polarized light cannot pass through the liquid droplet as it is amorphous structure. The emulsion is seen in a darkness as no polarized light able to pass through it. On the other hand, in Gaviscon suspension, a pitch black with yellow spots were observed. This is mainly due to crystal structure in solid particles of Gaviscon suspension that allow the passage of polarized light to pass through it. This is due to the crystal lattice of the solid particle that have space that enable polarized light to pass through it. Polarized light also used to observe directly the shape of solid particles and liquid droplets in suspension and emulsion respectively. Instead of using bright light microscope, we can use polarized light microscope which has more advantages in examining pharmaceutical formulations. Polarized light microscope can shows more clear and accurate shape of any particles or droplets in order to do the particle size analysis for a particular formulation.

4.      Describe the advantages and disadvantages of a microscope in determining droplet and particle size in pharmaceutical formulations.

Advantages of using microscope are they are relatively inexpensive, each particle can be examined individually by observing particles shape, 2D structure, colour, photograph can be taken for permanent record and small sample size is required. It gives convenience to the user as it provide a software to allow more accurate examination and adjustment for desired snapshot. Crystal like-structure of particle also can be examined and give very brief differentiation between crystal like-structure and amorphous structure. As for the disadvantages are every single particle need to be examined so this can cause error in examiner due to fatigue plus it is time consuming. It also give no information in 3D and very low throughput. Moreover, software use required manual.

CONCLUSION :

            Polarized microscope is best use to examine and determine the type of pharmaceutical formulation that cannot be differentiated by naked eye. Polarized microscope able to differentiate the crystalline and non-crystalline structure. The advance in technology of polarize microscope made the process to measure the diameter of particle or droplet become easy as there is camera and analyzer.