Formaldehyde (4%, w/v in PB)
MATERIALS
Reagents
NaOH (2 M) (optional; see Step 2)
Paraformaldehyde (EM Grade, purified, prill form) (Electron Microscopy Sciences, Inc.)
Equipment
Filter unit (disposable, 0.22 μm)
Tube (50 mL)
Water bath or incubator preset to 60°C
METHOD
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1. Dissolve 4 g of paraformaldehyde in 50 mL of H2O in a 50-mL tube.
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2. Heat at 60°C until dissolved.
Add a few drops of 2 M NaOH to help dissolve, if necessary.
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3. Cool to room temperature.
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4. Add an equal volume of 2X PB.
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5. Filter with a 0.22-μm disposable filter unit.
