Test strip longevity?

mome rath

splatter me with mustard
Mar 23, 2003
123
0
16
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Columbus, OH
Is there a point past which test strips for NH3, NO3, etc. are no longer viable? Anybody know the chemistry behind these?
 
I use test strips regularly. Every brand I've seen is date-stamped for expiration, and my experience has been that they no longer are accurate as that date passes. This is particularly true for strips that measure nitrate/nitrite and ammonia. I have strips for pH, GH and KH that don't seem quite so prone to inaccuracy after the expiration date.

HTH,
Jim
 
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