Ethidium bromide and propidi iodide

What are they?

Ethidium bromide is a fluorescent dye of the phenanthridinium salt family. Synonyms: 3,8-diamino-5-ethyl-6-phenylphenylanthridinium bromide; EtBr. Its molecular formula is C21H20N3Br, its molecular weight is 394.3 and its CAS number is 1239-45-8. Its physical appearance is solid and its colour is red.

Propidium iodide is a fluorescent dye of the same family as ethidium bromide. It is mutagenic, but to a lesser extent than ethidium bromide, and could replace it in most of its uses. Synonyms: 3,8-diamino-5-(3-(diethylmethylammonium)propyl)-6-phenylphenanthridine diiodide; propidium diiodide. Its molecular formula is C27H34N4I2, its molecular weight is 668.4 and its CAS number is 25535-16-4. Its physical appearance is powdery and its colour is red.

Ethidium bromide
propidium iodide

What are they mainly used for?

Ethidium bromide: a dye widely used in molecular biology to visualise DNA.

Propidium iodide: a dye widely used in cytology, particularly in cytofluorometry.

Both compounds are intercalating agents: they intercalate between the base pairs of nucleic acids. (Ethidium bromide intercalates mainly at the mitochondrial DNA level).

Why are they dangerous?

Ethidium bromidePropidium iodide
Hazard classificationThis product is classified as hazardous according to EU Directive 88/379 and concordant, on Chemicals and Dangerous Products.This product is classified as hazardous according to EU Directive 88/379 and concordant, on Chemicals and Dangerous Products.
Very toxicToxic
Warnings
  • Harmful in contact with skin and if swallowed.
  • Very toxic by inhalation.
  • Irritating to respiratory tract and skin.
  • Possible risk of irreversible effects.
  • Dangerous substance for the water supply system.
  • Do not inhale the powder.
  • Do not allow contact with eyes, skin or clothing.
  • Wash carefully after handling the product
  • Mutagen
  • Irritating.
  • Keep hermetically sealed.
  • Sensitive to light.
  • Hazardous combustion or decomposition products: toxic fumes of carbon monoxide, carbon dioxide, nitrogen oxides, hydrogen iodide.
Risk phrases (R-phrases)
  • R 39/26/27/28: very toxic: danger of very serious irreversible effects by inhalation, skin contact or ingestion.
  • R 46: may cause heritable genetic alterations.
  • R 46: may cause heritable genetic alterations.
  • R 36/37/38: Irritating to eyes, skin and respiratory system.
Indicative safety phrases (S-phrases)
  • S 7/8: Keep the container tightly closed, in a dry place.
  • S 20/21: Do not eat, drink or smoke during use.
  • S 56: Do not dispose of in drains or the environment. Dispose of it at a waste collection point.
  • S 60: Dispose of product and/or container as hazardous waste.
  • S 45: In case of accident, consult a doctor immediately (if possible, show the label).
  • S 26: In case of contact with eyes, rinse immediately with plenty of water and consult a doctor.
  • S 36/37/39: Wear appropriate clothing and gloves and eye and/or face protection.
  • S 22: Do not breathe the powder.

Destruction and decontamination procedures.

Destruction

  1. Put in a 250 ml container, under magnetic agitation, 100 ml of a solution containing 50 mg of ethidium bromide (0.5 mg/ml).
  2. Add 20 ml of a 5% hypophosphorous acid solution (stock solution: 90 ml of water plus 10 ml of 50% commercial hypophosphorous acid).
  3. Add 12 ml of an aqueous solution of sodium nitrite 0.5 M (34.5 g/l).
  4. Leave in agitation for a few minutes (progressive degassing).
  5. Let it stand for 20 hours.
  6. Neutralize with sodium bicarbonate.
  7. Eliminate the excess water.

It is likely that this technique can be used under the same conditions for the destruction of propidium iodide.

Descontamination

  1. Add to 100 ml of a solution containing 100 m g/ml (0.1 mg/ml) of ethidium bromide, 2.9 g of Amberlite XAD-16.
  2. After mixing for 20 hours, filter the mixture and classify the solid waste as hazardous waste.
  3. Discard the filtering, which should appear transparent.

For 100 ml of solution containing propidium iodide, it is necessary to use 5 grams of Amberlite XAD-16 resin.

Bibliographic references

  • Picot, A., Grenouillet, P. “Destruction du bromure d’éthidium et de l’iodure de propidium” a La Sécurité en laboratorire de chimie et de biochimie, cap IV.
  • “Disposal of ethidium bromide”. TIBS. June, 1994: 257-8.
  • Lunn, G., Sansone, E.B. “Ethidium bromide: destruction and decontamination of solutions”. Analytical Biochemistry 162 p. 453-458 (1987).