Sample Preparation for Electron Microscopes

Specimen preparation involves:

• fixation
• staining with heavy metals
• dehydration with solvents
• setting in resin and cutting thin sections (TEM)
• further staining (TEM) or coating with a conductive metal such as gold (SEM)

The steps to prepare a specimen for the SEM are as follows1. Primary fixation
Proteins are crosslinked by formaldehyde to stabilise them.2. Secondary fixation Lipid membranes are fixed with osmium tetroxide to prevent their extraction by solvents during dehydration. A black precipitate is formed on the lipids..3. Dehydration
The specimen is dehydrated using ethanol or acetone solutions. .4. Drying
The solvents are removed by drying.5. Mounting.
The specimen is mounted on a metal stub and coated with a conductive material such as gold.