I just got some Apera pH calibration fluid. I used up most of what came with the meter by storing the electrode in it. The pH 4 and 7 both expire in under six months. The storage fluid says it’s good for 10 months. 8oz is a lot of calibration fluid. So my question is can I use it after the expiration date or is it done for?
Good question @Outlaw Personally I start with a fresh small bottle of 4 an 7 PH Solution every grow. The main thing is to not contaminate your solution When doing a two point calibration also store in a dark place. Solution will last longer than 10 months , how much longer I’m not sure. Happy growing. 
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I have multiple ph pens at work and calibrate them all. The test fluid seems to last quite a while longer than stated, but i keep them in clean bottles with lids and only open when i have to. I use other pens to test my calibrations and havent had any problems yet at all.
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I agree. Transfer small amounts from 8oz bottle to single use sized containers so they don’t get Contaminated, and should last for a long time.
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