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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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