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Organic Peroxide Formers

Learn about campus requirements for work involving organic peroxide formers.

Organic peroxides are sensitive to oxygen, heat, friction, impact, light, and strong oxidizing and reducing agents. The unusual stability problems of this class of compounds make them a serious fire and explosion hazard that requires careful management.

Requirement for researchers

UC San Diego researchers working with organic peroxide formers must follow an approved hazard control plan (HCP) obtained through the Chemical Hazard Use Application (CHUA). This HCP must be preapproved by the principal investigator prior to beginning any work with this material. Information on this Blink page is supplementary and is not intended to replace the approved HCP.

Never work alone when working with hazardous chemicals.

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Identify and label organic peroxide formers

Learn to identify potential peroxide formers

  • Be aware that the following classes of chemicals include materials that form organic peroxides over time:
    • Aldehydes
    • Compounds containing benzylic hydrogen atoms (particularly if the hydrogens are on tertiary carbon atoms)
    • Compounds containing the allylic structure, including most alkenes
    • Ethers (especially cyclic ethers and those containing primary and secondary alcohol groups
      • MTBE (Methyl tert-butyl ether, also known as methyl tertiary butyl ether) is excluded from this policy and should be considered as a substitute for more hazardous ethers such as diethyl ether when possible.
      • Avoid diisopropyl ether when possible given how easily it forms peroxides.
    • Vinyl and vinylidene compounds

Labeling and inventory management

  • Label peroxide forming materials clearly and promptly upon receipt or synthesis (including refillable dispensing containers). Include this required additional labeling on peroxide formers (always include name or initials of person recording the information):
    • Date received (ex: 1/1/2010 RCVD, initials)
    • Date opened (ex: 1/1/2010 OPND, initials)
    • Date testing history (ex: 1/1/2010 ND or ‘X’ PPM, initials depending on results)
  • Review your inventory frequently to prevent peroxide formers from becoming unsafe.
  • Use a first in / first out inventory management system.

If you discover expired or old peroxide forming materials

  • DO NOT HANDLE ANY peroxide forming material that appears suspicious (oily, viscous, crystal formation) OR exceeds 80ppm using the test parameters outlined below (see the "Test for peroxy compounds" section).
  • Inform your principal investigator immediately.
  • Inform colleagues in the work area about the hazard.
  • Contact the Chemical Hygiene Officer and your Departmental Safety Officer as soon as possible.
  • Label and isolate the cabinet or area: “Do Not Handle – Dangerous Peroxide Forming Material”.
  • Contact EH&S Environmental Management Facility, (858) 534-2753, promptly for proper disposal.
    • See How to Request a Hazardous Waste Collection.
    • Important: Inform EH&S that the material is a suspect, possibly dangerous peroxide former so waste technicians are adequately warned about the hazards before waste disposal pick up or transport.

Test for peroxy compounds

  • Test all peroxide forming materials at least every 3 months.
  • Test prior to distillation or purification regardless of the material's age.
  • Never test containers of unknown age or origin, or containers that have reached their expiration date. Old bottles may contain concentrated peroxides or peroxides may have crystallized in the cap threads, presenting a serious hazard when opening.
  • All test records must be traceable. Reference all recorded container information to a written document (e.g., lab notebook). You can use the chemical inventory number on the container if applicable.
  • Prior to the expiration date on the container, you must test the material or it must be disposed of once expired.
  • If you are unsure about the safety of a material, properly dispose of it as hazardous waste.

Testing procedures

The 3 test methods below will detect most (but not all) peroxy compounds including hydroperoxides.

Peroxide check test stripsMethod 1. (Preferred)

  • Use peroxide semi-quantitative test strips with a range of 0-100 ppm (mg/L). Sensitivity and range (ppm or mg/L): 0.0, 0.5, 2.0, 5.0, 10, 25, 50 and 100. Quantity: bottle of 50. Available from Grainger (see image at right).
  • Record results in ppm on each container. Enter “ND” if peroxides are non-detectable.
    • 0-25 parts per million (ppm) - Compounds testing within this range offer little or no threat of violent reaction on the given test date. For compounds testing in this range, the investigator should consider the addition of fresh inhibitor to retard the auto-oxidation process and the container should be tightly sealed to prevent air and light exposure. Contents may be kept for another 3 months.
    • >25 and <50 ppm - Compounds originally inhibited by the supplier which test within this range may well be on the way to posing a threat to the operations of the laboratory. Remove peroxides or dispose of in a timely fashion.
    • >50 ppm - Any suspect container testing in this range must be considered to be potentially shock sensitive and should therefore not be handled further or moved. High peroxide concentrations may occur without the presence of visible crystals. Contact EH&S for proper disposal as soon as possible.

Method 2.

  • Add 1-3 ml of the liquid to be tested to an equal volume of acetic acid, add a few drops of 5% aqueous KI solution, and shake. The appearance of a yellow to brown color indicates the presence of peroxides and therefore the material should be properly disposed of.
    Note: This method is not quantitative.

Method 3.

  • Add 0.5 ml of the liquid to be tested to a mixture of 1 ml of 10% aqueous KI solution and 0.5 ml of dilute HCl to which has been added a few drops of starch solution just prior to the test. The appearance of a blue or blue-black color within a minute indicates the presence of peroxides and therefore the material should be properly disposed of.
    Note: This method is not quantitative.


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