2.5% glutaraldehyde fixative (electron microscopy) recipe
Firmly preserves ultrastructure for TEM and SEM: 2.5% glutaraldehyde in 0.1 M phosphate buffer pH 7.4.
🧮 Volume calculator
| Component | Amount | Final concentration (1X) |
|---|---|---|
| 25% glutaraldehyde (EM grade) | 1 mL | 2.5% |
| 0.2 M sodium phosphate (pH 7.4) | 5 mL | 0.1 M |
| Water (distilled) | to final volume |
Steps
- In a fume hood, mix the phosphate buffer and water, then add glutaraldehyde.
- Make fresh and use cold (4 °C).
- Fix for 1–2 h (small tissue overnight at 4 °C), then wash in buffer.
Good to know
- Not for immunofluorescence — glutaraldehyde causes strong autofluorescence and masks antigens.
- 0.1 M cacodylate buffer is also common but contains arsenic.
⚠ Safety Glutaraldehyde is toxic and a sensitiser — use a fume hood and gloves.
FAQ
Is it combined with PFA?
Yes — Karnovsky-type mixes (e.g. 2% PFA + 2.5% glutaraldehyde) combine fast PFA penetration with firm glutaraldehyde fixation.
This is a widely used standard composition. Amounts depend on the hydrate form and purity of your reagents — check the formula weight (FW) on the bottle and follow your institution's safety rules and the manufacturers' instructions.