Expired test kits with reference solutions

[StubbyAcro]

Can we trust expired test kits and use them up completely with reference solutions in hand? I’m talking about common test kits like Salifert and reference solutions like Fauna Marin Multi Reference and Tropic Marin Multi-Standard.

 

[The_Paradox]

They will have degraded precision but if you run two reference solutions and they come back accurate and repeatable I would still trust them.

 

[StubbyAcro]

I thought so too. Often, my test kits hit their expiration date while there’s still a lot of reagents left. I don’t want them to go to waste. I don’t think the expired test kits need to be accurate though, they just need to be precise. The true value we can get by checking with the reference solution.

I’m just worried the expired test kits degrade wildly between the reference solution checking, or becoming less precise.

 

[taricha]

Can you be specific about what those are test kits for? An alkalinity titration I would have very little worry about big shifts around expiration, but a nitrate test could be much more finicky and could drop to giving zero color.

 

[StubbyAcro]

I’m talking about test kits in general. If we’re strictly talking about Salifert, can you tell me which tests are more finnicky and which aren’t? In particular for these parameters:

• Calcium
• Magnesium
• Potassium
• Strontium
• Iodine
• Phosphate

 

[taricha]

If we’re strictly talking about Salifert, can you tell me which tests are more finnicky and which aren’t? In particular for these parameters:

• Calcium
• Magnesium
• Potassium
• Strontium
• Iodine
• Phosphate

The major ion titrations will be less finicky, I expect.
If Ca, Mg, K check out vs a current (not expired) reference solution, I'd think they work.
Sr tests are known to super difficult, even the bravest chem testers throw up their hands with them sometimes. and that's when they aren't expired!
Iodine - I know degrades over time.
Phosphate - I'd trust a sealed hanna packet past its expiration if it checked out vs a reference, but chemicals in bottles that get exposed to air over time, I'm less likely to trust.