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Formaldehyde prepared from paraformaldehyde is stable.
1Laboratory of Membrane Biology, West Los Angeles Veterans Administration Hospital Center/UCLA, California 90073, USA.
Summary
Freshly prepared formaldehyde (FA) solutions from paraformaldehyde are stable for days, reducing the need for immediate preparation or buffering during histological fixation.
Area of Science:
- Histology
- Biochemistry
- Materials Science
Background:
- Tissue fixation is crucial for histological investigations.
- Formaldehyde (FA) is commonly used, often prepared from paraformaldehyde (PFA).
- Purity of FA impacts histological outcomes.
Purpose of the Study:
- To assess the stability of freshly prepared formaldehyde solutions.
- To determine the impact of heating and storage on FA purity.
- To evaluate the necessity of immediate FA preparation and buffering.
Main Methods:
- Prepared FA solutions from PFA with and without heating.
- Measured solution pH and titrated acid content to quantify formic acid formation.
- Stored FA solutions for up to 8 days to assess long-term stability.
Main Results:
- Minimal acid formation observed during PFA heating.
- No significant increase in acid content upon prolonged heating or storage (up to 8 days).
- PFA depolymerization occurs at room temperature, negating the need for heating.
Conclusions:
- Formaldehyde prepared from paraformaldehyde is stable for extended periods.
- Immediate preparation of FA before fixation is unnecessary.
- Buffering of FA solutions may be omitted in many cases due to minor pH changes.