How long is calibration fluid good for?

[porpoiseaquatics]

I ask because my PH monitor is reading off compared to my API test kit. Granted, my test kit is old too but I figure it can't be that bad. So I knew I had some open calibration fluid and calibrated to that and now it's further off than it was originally. Anybody know how long calibration fluid is good for once you open it? (it's been kept in a sealed rubbermaid container since opened)

 

[dr_ fish]

Once it is opened, I would say the shelf life for it to be accurate is days.

 

[itsamyheff]

I have to agree with Drfish. I have been told one use and that is it. My question is why they supply you with that amount if it is only good 1 time.