Of all the questions we receive about Hypochlorous Acid, the question asked most often is how to extend the shelf life. The old thinking was HOCl has a shelf life of 4 hours, but their are steps you can take to make it last significantly longer. the most important being to stabilize the pH with an ideal target pH being 5.5 (this can be accomplished with Vinegar or Citric Acid).
The following steps when combined can prolong the shelf life of hypochlorous Acid for weeks, months or possibly longer.
- Stabilize the pH
- Upon making the HOCl store immediately in a bottle with an airtight seal
- Keep out of sunlight
- Keep it away from heat, ideally at 72 F or below
These steps can drastically increase the shelf life of HOCl. If you want to eke out a little extra shelf life, you can try filtering the water. Organic compounds cause HOCl to break down, so by eliminating the trace organic compounds that exist in tap water, in theory it should extend the life of the HOCl.
Instead of just relying on available studies and literature, we had wanted to perform our own test for a while, but haven't gotten around to it until today. We just made a batch of HOCl where we followed these steps (except for filtering the water). We'll be testing the water once a week and will keep you posted on exactly how much shelf life we can get out of it