Peroxide-Forming Chemicals

Some common laboratory chemicals can form peroxides on exposure to air. Peroxides are shock-sensitive and can be violently explosive in concentrated form or as solids. Others can result in rapid polymerization and can initiate a runaway, explosive reaction. The most commonly used peroxide-forming chemicals are: diethyl ether (ethyl ether), tetrahydrofuran (THF), dioxane. Isopropyl ether (diisopropyl ether) is a severe peroxide hazard. Organic peroxides are another class of compounds with unusual stability problems and as such are one of the most hazardous class of chemicals normally handled in the laboratory. Organic peroxides are listed in the Chemical Registry with "12" as the first two digits of the DDC number.

Due to the unstable nature of organic peroxides, it is necessary to contact the UMD EHSO at 726-6764 when discarding these chemicals.

Storage Procedures

The best way to manage chemicals that have the potential for forming shock-sensitive peroxides is to purchase only the quantity that is required in a one month period. Store the material in a tightly closed, properly labeled container in a flammable storage cabinet, away from flames, heat, sources of ignition, light, oxidizers and oxidizing acids.

Caution: All peroxidizable compounds should be stored away from heat and light. They should be protected from physical damage and ignition sources.

When peroxide-forming chemicals reach their expiration date, it is recommended that you process the chemicals for waste collection. If peroxide concentrations are greater than 80 ppm, call the Env. Health and Safety Office at 726-6764 (see Testing Procedure section below).

If a peroxide forming chemical is older than its expiration date or is stored longer than the time limits (see Table 5-2), follow these procedures:

Prior to moving the container, examine it.

1. Call our office at 726-6764 if crystals are visible in the chemical solution or if crystals are on or in the 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.

   Do not test these compounds for peroxides; let Chemical Waste Program personnel manage these containers.

2. Call the Chemical Waste Program if the container has a metal screw cap. Do not open the container. Metal capped containers
3. Call the Chemical Waste Program if the container has been stored longer than two years.

Leave the container where it was found until Chemical Waste Program staff arrive:

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 o

The following concentration guidelines apply:

r ignition. Tape-off the area containing the potentially shock sensitive compound and warn laboratory personnel of its presence.

Testing Procedures

Routinely test the chemical on a monthly basis, after its expiration date, for peroxide formation.

If you determine the container is safe to open:

Test the peroxide-forming chemical with a commercial test strip. Commercial test strips have a test range of 0.5 to 50 ppm (mg/L) or 3 to 100 ppm. If peroxides are greater than the concentration range measured by the test strip, a serial dilution with deionized water is necessary to determine a semi-quantitative concentration of peroxides.

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

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 Chemical Waste Program for packaging and removal.

Peroxide Inhibitor

If any peroxides are detected, a "dash" of butylated hydroxy toluene (BHT) should be added to the container to inhibit further peroxidation. Chemicals containing less than 80 ppm peroxides should have the BHT added, unless it is determined that the inhibitor will adversely affect experimental work.

Warning Label

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

Emergency Disposal

The UMD Env. Health and Office will have the Bomb Squad 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, or
4. the chemical is suspected to be shock-sensitive due to its age.

Table 5-2 Common Peroxide-Forming Chemicals

 

Severe Peroxide Hazard on Storage with Exposure to Air
Discard within 3 months
 

Peroxide Hazard on Concentration

Do Not Distill or Evaporate Without First Testing for the Presence of Peroxides
Discard or test for peroxides after 6 months

Hazard of Rapid Polymerization Initiated by Internally Formed Peroxides

Normal Liquids
Discard or test for peroxides after 6 months

Normal Gases
Discard after 12 months