Appendix A

Peroxide Test Protocol

Some common laboratory chemicals form peroxides when exposed to air (oxygen).  Peroxides are shock-sensitive and can become explosive in concentrated or solid form.  Others chemicals can polymerize quickly and initiate a runaway or explosive reaction. Organic peroxides are another class of compounds with unusual stability problems and, as such, are one of the most hazardous classes of chemicals normally handled in the laboratory. The most commonly used peroxide-forming chemicals are: diethyl ether (ethyl ether), tetrahydrofuran (THF), dioxane. Isopropyl ether (diisopropyl ether) is a severe peroxide hazard.

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Storage Procedures

The best way to manage chemicals that have the potential for forming shock sensitive peroxides is to purchase only the quantity that will be consumed in one year.

Store the material in a temperature-controlled area in a tightly closed, properly labeled container, preferably, in a flammable storage cabinet, away from flames, sources of heat, sources of ignition, light, oxidizing chemicals and oxidizing acids.

When peroxide-forming chemicals reach their expiration (testing cycle) date they must be tested for peroxides (see Testing Procedures section below). If peroxide concentrations are greater than 100 ppm, call the Environmental Health and Safety (EHS) office at 341-4305.

If a peroxide forming chemical is considerably older than its expiration or testing cycle date follow these procedures:

Prior to MOVING the container, examine it.

• Call EHS (ext. 4305) if crystals are visible inside or outside the chemical container. Closely examine the container near the cap for the presence of crystals. Some peroxide crystals in solution have a very fine, spun glass-wool appearance
• Call the Environmental Health and Safety office if the container has been stored longer than two years without being tested.

For the two scenarios above leave the container where it was found and contact Environmental Health and Safety (ext. 4305).

If the container was picked up, gently put it down in a safe place. Do not shake the container or place it near sources of heat or ignition. Warn laboratory personnel of its presence.

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Testing Procedures

Be sure your chemicals are logged into S&T’s Chemtrack program (contact EHS for this). Chemtrack will then automatically generate an email to the chemical owner each time it needs to be tested for peroxides.

If you determine the container is safe to open:

Test the peroxide-forming chemical with a commercial test strip (available from many chemical vendors). Commercial test strips have a test range of approximately 0.5 to 100 ppm. If peroxides are greater than the concentration range measured by the test strip contact EHS to have it properly disposed. EHS can also assist with the testing procedure.

Concerning results of the peroxide test, the following concentration guidelines apply: 

Alternate Peroxide Test:

The procedure listed below only indicates the presence of peroxides and does not indicate their concentration.

To 10 ml of a 20 percent aqueous solution of the unknown add:

1. Small spatula of sodium iodide or potassium iodide
2. Five ml of distilled water
3. Five ml of organic solvent (methanol or ethanol)
4. A few drops of concentrated hydrochloric or sulfuric acid
5. Small spatula of sodium iodide or potassium iodide
6. Five ml of distilled water
7. Five ml of organic solvent (methanol or ethanol)
8. A few drops of concentrated hydrochloric or sulfuric acid

An instant color change indicates the presence of peroxides

• yellow to faint orange = negligible amount of peroxides

• purple to dark violet or brown = peroxides present

If this procedure indicates a dark violet or brown color, call the Environmental Health & Safety office for removal and disposal.

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Warning Label

A warning label should be affixed to all containers of peroxidizable compounds, as illustrated below, to indicate the date of receipt, date the container was first opened, and dates it was subsequently tested:

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Emergency Disposal

The Environmental Health and Safety staff will arrange for an explosives demolition team to remove any containers of peroxide-forming chemicals if:

1. the chemical has a peroxide concentration of greater than 400 ppm,
2. the container has crystals in or on it,
3. the container is metal with a metal cap (does not apply to ethyl ether), or
4. the chemical is suspected to be shock-sensitive due to its age.

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Class of Chemicals That Can Form Peroxides (This section is taken from National Research Council’s Prudent Practices in the Laboratory, Handling and Management of Chemical Hazards, National Academy of Sciences, 2011, p. 72.)

Class A:  Chemicals that form explosive levels of peroxides without concentration

Class B:  These chemicals are a peroxide hazard on concentration     (distillation/evaporation).  A test for peroxide should be performed if concentration is intended or suspected.*

Class C:  Unsaturated monomers that may autopolymerize as a result of peroxide accumulation if inhibitors have been removed or are depleted*

*These lists are illustrative, not comprehensive.

SOURCES: Jackson et al. (1970) and Kelly (1996).