10% Formalin (4% Paraformaldehyde)

Author

Affiliation

Pranav Mishra

Rush University

Overview

The term “Formalin” specifically refers to a saturated solution of Formaldehyde, which is 37% w/v or about 40% v/v. This is a rather high concentration of formaldehyde. A common dilution is a 1:10, which is referred to as 10% Formalin or 4% Formaldehyde (aka 4% Paraformaldehyde). “Paraformaldehyde” technically refers to a polymerized form of formaldehyde which is stable at room temperature without the addition of methanol. Upon addition to an aqueous solution, it dissolves into formaldehyde by breaking the polymer chain.

Uses

Fixing tissue

Components

1. \(diH_2O\)
2. \(HCl\) (Dilute)
3. \(NaOH\) (1 N)
4. Paraformaldehyde powder (Sigma Aldrich Cat 158127-500G)
5. 1X Phosphate Buffered Saline
6. Sterile container

Protocol: Preparation of 1 liter of 4% PFA (10% Formalin)

Adapted from¹

1. In a vented hood, add 800 mL of PBS to a beaker with a stir bar on a hot plate set to \(60 ^\circ C\)
2. Add 40g of PFA powder to the heated PBS solution
3. Spin until mostly disolved ¹
4. Raise the pH, by adding 1N \(NaOH\) dropwise using a transfer pipette, until the solution clears ²
5. Cool to room temperature
6. Add 1x PBS until the volume reaches 1L total

Storage

• Ideally, this should be prepared fresh for each use
• \(2-8 ^\circ C\): 1 month
• \(-20 ^\circ C\): several months

References

1. R&D Systems. Protocol for Making a 4% Formaldehyde Solution in PBS. https://www.rndsystems.com/resources/protocols/protocol-making-4-formaldehyde-solution-pbs

1.

R&D Systems. Protocol for making a 4% formaldehyde solution in PBS. R&d systems. Accessed March 31, 2023. https://www.rndsystems.com/resources/protocols/protocol-making-4-formaldehyde-solution-pbs

Footnotes

1. Note: the solution will appear like milk

2. Note: Takes \(\le\) 2 mL of 1N \(NaOH\) to turn the solution clear.

Citation

BibTeX citation:

@online{mishra2023,
  author = {Mishra, Pranav},
  title = {10\% {Formalin} (4\% {Paraformaldehyde)}},
  date = {2023-06-09},
  url = {https://github.com/pranavmishra90/research-reference/protocols/recipes/solvents/formalin (10 percent).html},
  langid = {en-US}
}

For attribution, please cite this work as:

Mishra P. 10% Formalin (4% Paraformaldehyde). Published June 9, 2023. https://github.com/pranavmishra90/research-reference/protocols/recipes/solvents/formalin (10 percent).html