Last Revised: April 12, 2024
Revision 5/2020
This Fact Sheet gives hazard information and precautions for the preparation of Piranha solution and is a supplement to SOP: Corrosives and SOP: Strong Oxidizers, which must first be read and understood by anyone planning to work with this chemical.
Piranha is a mixture of concentrated sulfuric acid and hydrogen peroxide (between 3:1 and 7:1) used to remove trace amounts organic residues from substrates such as glassware. The active ingredient is peroxymonosulfuric acid, which is highly reactive and efficient for the oxidation of organic materials. The oxidation is extremely exothermic and can potentially lead to an explosion. This is why Piranha is NOT to be used as the primary remover of organic materials!
A closely related mixture, sometimes called "base piranha", is a 3:1 mixture of ammonia water with hydrogen peroxide. This Fact Sheet focuses primary on acid piranha. A separate hazard assessment should be performed for preparation and use of base piranha solution.
More information on Piranha can be found in the Safety Alert: Piranha and Gas Producing Mixtures.
A Hazard Control Plan (HCP) may be required for the use of Piranha.
Examples of when an HCP is required is whenever a lab is using piranha for the first time, whenever the PI nor lab members have previous experience working with these solutions, or when conditions such as heating the solution are required.
All work with Piranha requires the approval of the P.I. The P.I. must determine whether the person or team who will be working with the chemical must write a task-specific Hazard Control Plan (HCP). EHRS will upload the HCP to the “documents” section of the lab’s BioRAFT page.
The P.I. must also ensure that the person or team who will be working with the chemical understands the hazards and has received adequate training and supervision for the procedure.
If you have any questions about whether an HCP is needed or how to adequately train personnel or supervise this procedure, contact EHRS for assistance.
Less hazardous alternatives to Piranha should be used where feasible. For cleaning purposes, NoChromix, Nano-strip and a KOH/ethanol bath are excellent alternatives to Piranha baths. Nano-strip is also an alternative for Piranha etching processes. These solutions are also hazardous and reactive, but they are more stable and have consistent concentrations of the peroxymonosulfuric acid. Contact EHRS if you need guidance on the safe handling of these Piranha alternatives.
Piranha solution must be prepared fresh for use. Only prepare enough Piranha to be used immediately. Do not store leftover Piranha.
All solutions must be prepared in a fume hood and using clean, dry glassware or Teflon. Do NOT use plastics as they are incompatible with the Piranha solution. Work with the fume hood sash between you and the solution.
Use Concentrated sulfuric acid and a 30% hydrogen peroxide solution are used to prepare the solution. Do not use 50% or higher hydrogen peroxide due to potential overheating and explosion [1].
Add the hydrogen peroxide to the sulfuric acid slowly, stirring slowly to combine. The vessel will get warm as the components are mixed. Any batches larger than 100 mL need to be cooled in an ice bath.
Always allow the solution to equilibrate to room temperature before use.
Do not seal any containers of Piranha, for example—with a tightly sealing lid, as pressurization and container rupture can occur.
Lab attire and Personal Protective Equipment must be in accordance with Penn’s Lab Coat, Gloves and Safety Eyewear Policy.
Acid resistant gloves, face shield and an acid-resistant apron is required for batches larger than 500 mL.
Disposal of used or unneeded Piranha solution must follow the guidelines outlined in the EHRS Fact Sheet: Gas-Producing Waste.
Fact Sheet: Gas-Producing Waste
Safety Alert: Piranha and Gas Producing Mixtures
References
[1] P.G. Urben (Ed.), Bretherick’s Handbook of Reactive Chemical Hazards 6th Ed., Oxford, Butterworth-Heinemann, 1999