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7/31/2019 Applications of Scanning Electron Microscopes in Pharmaceuticals
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Outline
Introduction Definition of Terms
Scanning Electron Microscope
Brief History Specifications
Preparation of Sample
Strengths and Limitations
Applications of Scanning ElectronMicroscope in Pharmaceuticals
References
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Definition of Terms
SEM – Scanning Electron Microscope
Sputter Coating - a gold target is
bombarded with heavy gas
atoms. Metal atoms ejected from thetarget by the ionised gas cross the
plasma to deposit onto the any surface
within the coating unit including thespecimen.
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History
Max Knoll, who in 1935 obtained an image
of silicon steel showing electron channeling
contrast
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The SEM is an instrument that produces
a largely magnified image by usingelectrons instead of light to form an
image.
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Principle of SEMThe electron
beam follows a vertical path through the
microscope, which is held within a vacuum
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Principle of SEM
Once the beam hits the sample,
electrons and X-rays are ejected from
the sample
Detectors collect these X-rays,backscattered electrons, and secondary
electrons and convert them into a signal
Signal is viewed in a television whichproduces the final image.
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Specifications
Magnification: 15x to 200,000x
Resolution: 5 nanometers
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Sample Preparation
All water must be removed from thesamples because the water wouldvaporize in the vacuum.
All metals require no preparation beforebeing used.
All non-metals need to be madeconductive by covering the sample with
a thin layer of conductive material (goldfoil). This is done by using a devicecalled a "sputter coater."
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Strengths and Limitations
Strengths
Critical in all fields that require
characterization of solid materials.
Comparatively easy to operate, with user-friendly "intuitive" interfaces.
Require minimal sample preparation.
Modern SEMs generate data in digital
formats.
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Strengths and Limitations
Limitations
Samples must be solid
Must fit into the microscope chamber:
horizontal dimensions and verticaldimensions should not exceed beyond 10
cm and 40 mm, respectively.
Samples must be stable in a vacuum on the
order of 10-5 - 10-6 Torr.
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Applications of SEM in
Pharmaceuticals Scanning electron microscopy (SEM)
provides a qualitative assessment of powders or compressed dosage forms interms of: Size
Shape
Morphology
Porosity
Size distribution
Crystal form
Consistency
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Applications of SEM in
Pharmaceuticals
This information can be correlated to
assess dissolution behavior,
bioavailability, and crystalline structure.
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Applications of SEM in
Pharmaceuticals
Particle Contamination
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Applications of SEM in
Pharmaceuticals
Particle Contamination
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Applications of SEM in
Pharmaceuticals
Identification of Trace Metals
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Applications of SEM in
Pharmaceuticals
Product Defect Analysis
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Applications of SEM in
Pharmaceuticals
Reverse Engineering
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References
http://www.intertek.com/analysis/microscopy/
sem/
http://www.fei.com/uploadedfiles/documents/
content/2006_06_quanta_pharma_pb.pd http://pubs.rsc.org/en/Content/ArticleLanding
/2012/AY/C2AY25031D#!f
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