Purchase quantities of peroxidizable compounds according to short-term needs. For instance, buy several 100-mL cans of diethyl ether instead of one 1-L can. Even though this might be more expensive per volume, this purchasing method helps prevent expiration and product loss, and reduces the peroxidation potential. Purchases corresponding to use requirements help minimize exposure to air from multiple openings of the container. A tight cap on a nearly full bottle provides effective protection against peroxide formation.

You can keep peroxide accumulation low by storage in reasonably full containers (25% maximum headspace) with TIGHT caps that you replace promptly after use. Further protection is available when you flush the headspace over peroxidizable compounds with nitrogen (inert gas) before closing the container. Vinyl monomers (Appendix 13-A, Table I, List C) containing certain inhibitors are exceptions and require air in the headspace.

Oxidation inhibitors are useful, and recommended by several chemical manufacturers. Hydroquinone, alkyl phenols, aromatic amines, and other oxidation inhibitors are effective in preventing peroxide formation during storage of peroxidizable compounds. If you add an inhibitor, make sure it is compatible with use or purity requirements of the compounds. Follow a program of periodic testing and replenishing inhibitor levels during storage of peroxidizable materials.

As part of the Laboratory Safety Plan, your research group must maintain an inventory of peroxidizable compounds and review it twice a year. Discard those compounds that are out of date. The EHS Safety Labels webpageincludes a printable label on which you can enter the date you received a peroxidizable material, date opened, and date to evaluate, treat, or discard.

Evaluate List A (Appendix 13-A, Table II) materials for peroxide content at least every three months after opening, followed by re-dating if safe, treating or discarding. Before disposing any List A materials, review the properties of the material (preferably with EHS consultation) to ensure safe disposal.

Do not store List B (Appendix 13-A, Table II) materials in your lab for longer than 12 months after opening, unless a suitable test shows they have not accumulated peroxide. If List B materials give a significantly positive test (red by the ferrous thiocyanate test) you must retain them, treat to remove peroxide, repackage, show by test to be peroxide-free, and then re-date the label.

List C (Appendix 13-A, Table II) materials should not be stored for longer than 12 months, unless test results show them to be peroxide-free. Commercial vinyl monomers usually contain additives that inhibit peroxidation. Generally, you should store inhibited vinyl monomers under air rather than nitrogen or other inert atmosphere, because customary inhibitors are phenolic compounds, which require oxygen for their action. Isolation of uninhibited (and hazardous) vinyl monomer is usually not necessary, since most vinyl monomers can polymerize without removal of inhibitor by proper adjustment of initiator concentration.

Uninhibited List C materials can be a significant hazard. Do not store more than 500 grams of uninhibited monomers for longer than 24 hours. Smaller samples (less than 10 g) may be stored longer than 24 hours with discretion. Generally, storage of uninhibited vinyl monomers should be under nitrogen and below room temperatures. For storage in excess of 24 hours, add a suitable inhibitor, with its name and quantity on the label.

The suggested safe storage period if unopened from manufacturer is up to18 months from receipt or stamped expiration date, whichever comes first.

Each container of peroxide-forming chemicals must have the following dates written on the label:

  1. Date Received
  2. Date First Opened
  3. Date to be Discarded

You may use the label available from the EHS Safety Labels page to enter these dates. When you chemically remove peroxides, make a notation on the label to indicate the new disposal date.

Store peroxide-forming chemicals together in full, airtight, opaque containers at temperatures below 30°C (86°F) and in the dark. Use only refrigerators designated “explosion-proof”.