Can hydrogen peroxide expire?

By Jillian Jastrzembski

You may have heard that hydrogen peroxide, or H2O2, is an extremely unstable molecule that is just hankering to lose that extra oxygen and become water.

You may also have been storing the same bottle of hydrogen peroxide in the back of your bathroom cabinet since the mid-90s.

So, what’s the deal? Does hydrogen peroxide expire, or is that bottle still good?

In this article, we’ll cover:

•       Can hydrogen peroxide expire?
•       How long can you store hydrogen peroxide?
•       How do you know if hydrogen peroxide is no longer good?

What is hydrogen peroxide?

Hydrogen peroxide is a ubiquitous household chemical with the chemical formula H₂O₂. It exists as a clear liquid at room temperature with no odor. It was first discovered in 1818, and has been used as a disinfectant since as early as the 1890s.

Hydrogen peroxide is best known for its strong oxidizing properties. It is a safe and environmentally-friendly broad-spectrum disinfectant in the medical, food, and environmental industries. Endogenous hydrogen peroxide also plays a critical physiological role in cells.

When you look at the chemical formula for hydrogen peroxide, you may be struck by its resemblance to water, H₂O. In fact, hydrogen peroxide does break down to form water and oxygen when exposed to heat or light. The chemical reaction looks like this:

2H₂O₂ → O₂ (g) + 2H₂O (l)

In fact, this is what makes hydrogen peroxide a greener choice for cleaning reagents compared to alternatives like chlorinated solvents. Because it breaks down into these innocuous constituents, it does not have a negative environmental impact.

Beyond that, hydrogen peroxide is also produced naturally within cells. Endogenous hydrogen peroxide is an important mediator in innate immunity, healing, and apoptosis (programmed cell death). Your cells are equipped with special antioxidant compounds that help to otherwise protect them against endogenous hydrogen peroxide. However, when introduced extracellularly, hydrogen peroxide can still be harmful to cells. That is why it is not advisable to use hydrogen peroxide to clean wounds.

How long can you store hydrogen peroxide?

Despite its reputation, hydrogen peroxide is actually a very stable molecule under the right storage conditions. This is why hydrogen peroxide tends to be sold in dark containers, which protect it from light exposure. It should also be stored at ambient or cool temperatures to help prevent degradation.

Most recommendations advise replacing hydrogen peroxide every 1-2 years. Under dark, ambient storage conditions, hydrogen peroxide has been reported to degrade at a rate of less than 2% per year. Based on this, you can store hydrogen peroxide for quite a long time with minimal loss of potency. It depends on your storage conditions, your starting concentration, and your desired application. Most household hydrogen peroxide is sold at a concentration of 3% in water. Lab Alley sells hydrogen peroxide in varying concentrations, ranging from 3% to 34%.

If your hydrogen peroxide is only partially degraded, it may still be effective. Hydrogen peroxide is an effective disinfectant over a broad concentration range.

How do you know if hydrogen peroxide is no longer good?

If you’re wondering if you need to replace your hydrogen peroxide, you can try the potato test. All you need to do is pour a bit of hydrogen peroxide over a slice of potato. If it fizzes, then your hydrogen peroxide still has some potency. If there is no fizzing, then your hydrogen peroxide has likely degraded to water.

The reason this works is because the potato cells contain catalase. Catalase is an enzyme which exists in almost all cells, which can break down hydrogen peroxide into water and oxygen. The oxygen creates gas bubbles in the water, which makes it fizz.

This isn’t specific to potatoes, however. As we said, almost all cells contain catalase. This is part of the body’s way of protecting you against endogenous hydrogen peroxide. Catalase is also the reason why hydrogen peroxide fizzes when you pour it on a wound.

Can hydrogen peroxide expire?

In conclusion, yes, hydrogen peroxide can expire. But if you store it in an opaque container at room temperature, it will do so very slowly. During storage, it will gradually lose potency as it decomposes to form water and oxygen. Pay attention to the starting concentration and the minimum effective concentration for your application.

Lab Alley is pleased to provide you with the highest quality hydrogen peroxide for your industry needs whenever you’re ready to restock.

If you have additional questions about hydrogen peroxide or any of our products, please don’t hesitate to contact us for assistance

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