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Neptune Trident calibration fluid reuse?

JVU

President
BOD
I know the bottle says that the Trident calibration fluid is only good for 8 hours after opening. I understand why that would be true if it were left open to the air for an extended period. But if it were used, then closed air-tight, I don’t see why it couldn’t be reused later for a second calibration, for example at the beginning of the second month after switching out reagent A. I often find that that is when my numbers start to get wonky and I need to recalibrate.

Two questions-

1. Do you guys have real-world experience with this either way?

2. @Vhuang168 or other knowledgable insider if you are willing could you give a straight-talk answer about this? And if it is true that the fluid expires is there a scientific explanation?

I’m currently frustrated because my Alk Trident reading just nose-dived today for no apparent real reason, so I’ve been trouble shooting each part, manually rechecking values, and I’m finding all 3 readings are off unacceptably so I need to recalibrate, among other things.
 
Thanks! I rummaged around and found an unopened bottle of calibration, using it now. But I’m still interested in the answer to this for future reference.
 
I am curious to the answer to this because I recently had a bottle of reagent A that was completely off and I ended up tossing all the reagents and using new ones with new calibration fluid that came with it.
 
I reuse my calibration fluid even after months of opening... typically I see very little change from published values. BUT, I am not using the liquid calibrate (usually) but more of a sanity check when I suspect my measurements are off.

To me, I always wondered about the shelf life of the calibration bottles being that they aren't really sealed tightly in the bottles to begin with. And while air does get into the calibration solution when you open the bottle, what does ambient air really do to oxidize alk, ca, and mg? to me, evaporation is probably the biggest variable. but if you reseal the bottle tightly after initial use, the fluid should be good enough for a sanity check...

One thing that @Vhuang168 did advise is that you can calibrate using your tanks water if you know the values of the water. So in a hard pinch, I would probably measure with Hanna... and then calibrate based off those values...granted there'll be some margin of error but probably within realm of acceptability.
 
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We use certain processes that ensure the alkalinity stays stable from when we test the solution to when you 1st open the bottle. Once the bottle is open, the alkalinity levels will start to change..
 
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