What is the Difference Between Formaldehyde and Paraformaldehyde?
🆚 Go to Comparative Table 🆚The main difference between formaldehyde and paraformaldehyde lies in their chemical structure and usage:
- Formaldehyde is a small molecule that is a gas at normal conditions. It is the simplest aldehyde and is often used as a tissue fixative in histology and cell biology.
- Paraformaldehyde (PFA) is a polymer of formaldehyde, also known as polyoxymethylene. By itself, paraformaldehyde is not a fixing agent and needs to be broken down into its basic building block, formaldehyde, to be usable as a tissue fixative. This can be done by heating or basic conditions until it becomes solubilized. Paraformaldehyde is commonly used in research settings and can substitute 10% formalin.
Formalin is a saturated formaldehyde solution in water (37% by weight, 40% by volume) containing 10-15% methanol. Methanol is added to slow down the polymerization to formaldehyde, which reduces the fixing power of formalin. Formalin can also be made in an alcohol-free form from powdered paraformaldehyde. A protocol calling for 10% formalin is roughly equivalent to 4% formaldehyde.
In summary, formaldehyde is a gas used as a tissue fixative, while paraformaldehyde is a polymer of formaldehyde that needs to be broken down into formaldehyde to be used as a tissue fixative. Formalin is a saturated solution of formaldehyde with added methanol.
Comparative Table: Formaldehyde vs Paraformaldehyde
Formaldehyde and paraformaldehyde are both types of aldehydes used in various applications, such as cell fixation in immunohistochemistry and fluorescent protein labeling. Here is a table summarizing the differences between the two:
Property | Formaldehyde | Paraformaldehyde |
---|---|---|
Chemical Formula | CH2O | CH2O (polymerized) |
Form | Gas at normal conditions | Solid polymer |
Solutions | Formalin (a 37% saturated solution) | Diluted in water or buffer for use |
Cross-linking Ability | Yes | N/A (breaks down into formaldehyde) |
Applications | Fixation solution for immunohistochemistry and fluorescent protein labeling | Fixation solution for immunohistochemistry and fluorescent protein labeling |
Commercial Availability | Yes, as formalin solution | Solid polymer that can be diluted to prepare a solution |
Composition | Single aldehyde molecule | Consists of 8-100 formaldehyde units |
pH Adjustment | Typically 80% Formalin has pH 6.9 to 7.4 (adjusted with 1N HCl or 1N NaOH) | Typically dissolved in a buffer (like PBS or TBS) at 70°C with several drops of 5N NaOH to help aqueous solubility |
Paraformaldehyde is a polymer of formaldehyde and is not a fixing agent itself. When dissolved in water or a buffer, it breaks down into formaldehyde, which is the actual fixing agent. Both formaldehyde and paraformaldehyde can be used as fixation solutions for immunohistochemistry and fluorescent protein labeling.
- Formalin vs Paraformaldehyde
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- Formamide vs Formaldehyde
- Formaldehyde vs Acetaldehyde
- Aldehyde vs Formaldehyde
- Urea Formaldehyde vs Melamine Formaldehyde
- Methyl Paraben vs Propyl Paraben
- Paraben vs Paraffin
- Benzaldehyde vs Benzophenone
- Methyl Paraben vs Sodium Methylparaben
- Acetaldehyde vs Acetone
- Ortho Nitrophenol vs Para Nitrophenol
- Benzaldehyde vs Acetophenone
- Buffered Unbuffered vs Neutralized Formalin
- Benzoic Acid vs Benzaldehyde
- Peroxide vs Hydrogen Peroxide
- Oxo vs Formyl
- Ortho vs Para Nitrophenol