[FunkyB]

I work for a biochemical company and had a discussion over the proper expiry date for MilliQ water.

We use this MilliQ-water for our systems (HPLC, IC, Biacore,TOC) but the procedures don't describe how long you can use the same water.
We know that it's important to use new water every day for the TOC-test, because CO₂ can cause troubles otherwise. But the rinsing water for HPLC and other systems is used for a longer time (most cases 1 week).

I searched USP en PhEur but couldn't come up with a resolution.
Can someone give me an answer to this? (maybe with a link to a guideline?)

Thanks!

[Arkcon]

It will depend on the local conditions in your lab, and you will have to try and determine it experimentally, develop a policy, and verify it for your self, unfortunately.  I've been places where purified water began to visibly grow white bread mold in just a few days, and others where it's been kept indefinitely, and other places that never stored water, it was always fresh from the purification system, just to be secure.

[kikistare]

Bacteria can grow in the water very easily. We do a lot of work with HPLC analysis in my lab. The FDA recently told us that we had to renew the water in the plastic squirt bottles everyday and throw out any vendor bottles of water after they have been opened for 7 day. If the water is mixed with organic solvent then we usually give it a month expiration because the organic inhibits the growth of bacteria.

[FunkyB]

We also renew the water in our plastic squirt bottles every day and even our approach on the opened bottles en mixing it with solvents is the same as yours. But this isn't documented yet and I was wondering if there were any regulations about it, just to be sure before we take this into your work instructions.

Thanks for the info!