Hanna phosphate regents

[mheaven]

Hello everyone, the Hanna phosphate regents come with an expiration date.

Has anyone used them past the date?
Do they're really expire or is this just another way to get you to buy more every year?

I have about 80 left from when I purchased my Hanna meter and would hate to throw them away if I could still use them.

Thanks,
Danny.

 

[Dan_P]

Hello everyone, the Hanna phosphate regents come with an expiration date.

Has anyone used them past the date?
Do they're really expire or is this just another way to get you to buy more every year?

I have about 80 left from when I purchased my Hanna meter and would hate to throw them away if I could still use them.

Thanks,
Danny.

Chemicals degrade with time, some faster than others. Expiration dates might be selected arbitrarily or might be based on testing the potency over time. Let's assume the less cynical view and say it is based on potency.

In this case, the expiration date is based on a percentage potency left after a certain amount of storage time at room temperature, let's say 90% for illustration purposes. For all practical purposes the potency is the same the day before as it is the day after the expiration date. But as the time past the expiration date increases, the less potent the chemical becomes and the more inaccurate the test result involving it.

Since we don't know how quickly chemicals degrade, we cannot adjust the results to account for the declining potency. It is prudent not to use expired chemicals, although a few months over is not likely a problem, but a year, I wouldn't chance it if accurate test results are important to you.