Department of Biology
Use of Peroxide Forming Chemicals
Peroxide forming chemicals (such as diethyl ether and tetrahydrofuran) present a danger because of the possibility of high levels of peroxides forming (e.g. during long-term storage or when a sample containing such chemicals are concentrated using rotary evaporation) which can cause a spontaneous explosion.
Whilst activities involving vacuum distillation and rotary evaporation present the greatest risk of generating dangerous levels of peroxides, peroxides can form in many types of ether by simple reaction with atmospheric oxygen during storage. Indeed, a spontaneous explosion of a bottle of diethyl ether in this Department several years ago is thought, retrospectively, to have been caused by high levels of peroxide that built up during years of storage.
The Department has introduced some simple measures to minimise the risk from the formation of peroxides.
Why do peroxide forming chemicals present a hazard?
Peroxides can form in many ethers (and other chemicals) by simple reaction with atmospheric oxygen during storage. If the peroxides become concentrated, they can form exceedingly sensitive substances which can explode spontaneously and destructively. For example, a dangerous concentration of peroxide can build up if an ether, containing peroxides, has most of the ether removed by vacuum distillation or rotary evaporation.
Steps to be taken to minimise the risk from the formation of peroxides
1) Store ethers (and other peroxide forming chemicals) properly
Since peroxides are formed by an auto-oxidation process:
- Always Keep Bottle Sealed when not in use to prevent the free ingress of air.
- Store in the Dark, Do Not Store in Sunlight - the auto-oxidation reaction can be photoinitiated.
- Store in a Cool Place . The auto-oxidation process is faster at higher temperatures.
2) Wherever possible use ethers (and other peroxide forming chemicals) that contain antioxidant and buy the minimum necessary for the work planned
Many ethers and other peroxide forming chemicals that are supplied to the Department contain stabilisers which prevent the build-up of dangerous levels of peroxides. In general, these ethers can be used for general laboratory work, including use as solvents which can be removed by distillation or rotary evaporation.
It is also important to avoid the purchase of large volumes (e.g. 2.5 litres) of peroxide forming chemicals which are not needed. Buy only the minimum needed even if the chemical is cheap.
3) Label bottles of ethers (and other peroxide forming chemicals)
As peroxides are formed by an auto-oxidation process, their concentration builds up with time. All ethers and other peroxide forming chemicals will be labelled to indicate the date of receipt and a “use by” date on them (2 years after receipt). A label (see example below) will be attached to all bottles of uninhibited or inhibited ethers by Biology Stores on delivery.
Warning!Peroxide Forming Chemical |
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Date of Receipt |
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Do Not Use After (no more than 2 years after receipt) |
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Tested for Peroxide |
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Date |
Level |
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Example of label to be added to peroxide forming chemicals
4) Check peroxide levels in ethers (and other peroxide forming chemicals)
It is recommended that peroxide levels in Ethers are periodically checked to ensure that levels remain safe. Rapid and user-friendly commercial test strips are available free from Biology Stores.
Frequency of Peroxide Checks
- Inhibited Ethers and other peroxide forming chemicals : it is recommended that these should be tested every 6 months
- Uninhibited Ethers and other peroxide forming chemicals : it is recommended that these are checked on opening, and every 3 or 6 months subsequently
- For use in vacuum distillation / evaporation: Check immediately prior to use
Level of Peroxide Detected
- 0 to 30 mg/l
Acceptable for all routine lab work, including vacuum distillation and evaporation to dryness. Note however, that even with less than 30 ppm of peroxide, if a very large volume of ether is distilled to dryness then a noticeable level of peroxide could, potentially, still build up. Therefore, ensure that the quantity of ether being used is as small as is necessary
- Greater than 30 to 100 mg/l
Acceptable for all routine lab work EXCEPT vacuum distillation and evaporation to dryness. If the peroxide level is approaching 100 ppm then it should be considered for disposal via Biology Stores; label bottle as waste as normal and record the level of peroxide.
- Greater than 100 mg/l
DO NOT USE. Contact Departmental Safety Advisor as soon as possible. If the level of peroxide is greater than 100 mg/l then the peroxide test strip will either be darker blue than the 100 mg/l colour reference chart, or turn brown. In this event, the ether contains a significant level of peroxide and should be treated as hazardous. Contact the Departmental Safety Advisor as soon as possible, label as not to be used, inform other lab workers and isolate the bottle.
List of organic species known to form peroxides
Certain species are more prone to peroxide formation than others (this list is for guidance only and is not exhaustive).
1) Severe Peroxide Hazard on Storage with Exposure to Air
Check for peroxides every three months and dispose of after two years
Di-isopropyl Ether (isopropyl ether)
Divinylacetylene (DVA)
1,1 dichloroethene (Vinylidene Chloride)
2) Peroxide Hazard on Concentration
Check for peroxides every six months and dispose of after two years
Acetaldehyde diethyl acetal (acetal)Ethylene glycol dimethyl ether (glyme)
Cumene (isopropylbenzene)
Ethylene glycol ether acetates (ethanediol)
Cyclohexene
Cyclopentene
Furan
Decalin (decahydronaphthalene)
Methylacetylene
Diacetylene (butadiene)
Methylcyclopentane
Dicyclopentadiene
Methyl isobutyl ketone
Diethyl ether (ether)
Tetrahydrofuran (THF)
Diethylene glycol dimethyl ether (diglyme)
Tetralin (tetrahydronaphthalene)
Dioxane
Vinyl ethers
3) Hazard of Rapid Polymerization Initiated by Internally Formed Peroxides
Discard or test for peroxides 6 months after opening
Chloroprene (2-chloro-1,3-butadiene)
Vinyl acetate
Styrene
Vinylpyridine