I'm working on some quality system things and trying to find something documented somewhere officially as to the shelf life of Reagent grade salts such as used in salt solution method for RH calibrations (such as Sodium Chloride, Lithium Chloride, Potassium Sulfate). I went to the Mallinckrodt website and the best I could find was in their Q&A's they said some chemicals may have a "RE-TEST" date listed. None of the above chemicals do.
We have a chilled mirror system that we periodically bump against (and use for most cals), and according to my highly experienced tech, he has yet to see any fluctuation in the quality of the salts (regarding cal results).
I don't want to just do something that will shut an auditor up. I would really like to get something definitive as to the REAL shelf life of these salts. It seems like something as basic as Sodium Chloride, unless it gets contaminated (i.e.: keep the lid tight in a cool, dry place) it should last a very long time.
So anyone ever found anything at least somewhat definitive as to shelf lives of such chemicals?
This is the only one I'm aware of and it really isn't very impressive.
http://www.swisserv.com/Rotronic/catalogo/calibracao.pdf
It gives a 10 year limit, but it's referring to sealed vials.