how long is a test kit good for?

concerning the ammonia kit i got the other day. its a prodac brand one (never heard of the brand personally) but the box seems a little old but inside everything wasnt opened so i bought it.

but my result from the day i got it till now is always 0.5 mg/l .... does the solution go bad even if its sealed?? i read somewhere most ppl say after open test kit usually last 6 month but no one mention if its possible to go bad if it wasnt open.

 

I'm not at all familiar with that brand but I tend to not trust test kits once I've had them for a year. Some test kits have an expiration date printed on them so that does help.

 

Generally depending on the concentration/nature of the reagents, laboratories would need to re-standardise at least monthly.

From my experience I would say about 6 months to a year one should be OK. Generally over time the reagents (ones you add dropwise - not the indicators) would tend to get "weaker" so would overstate any results you get. If the results vary by 5-10% or so from actuals you should not have too many problems really.

Clinton