Stability / expiry of reference standards

Discussions about methods and best practices across food quality, safety and authenticity testing.

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Dear colleagues
Assume you know that a substance is stable in stock solution and under controlled and defined storage conditions for a certain amount of time. This is tested and confirmed fulfilling all regulatory needs. Is it then reasonable to prepare a stock solution that expires later than the reference standard's expiry date?

In my opinion: Yes, because the expiry date from the CoA tells me that the quality of the reference standard is given until this date. So I can expect the solution of guaranteed quality to be stable for the known amount of time.

Looking forward to arguments supporting or proving wrong my argumentation. Or maybe there is official guidance to this question?

Best regards
Jörg
bunnahabhain wrote:
Is it then reasonable to prepare a stock solution that expires later than the reference standard's expiry date?


We did. We documented stability of our in-house reference standard solutions stored in a refrigerator over like a 6-month interval. I'm sure there were times that the "expiration date" of the original reference material had passed.

In my opinion, many manufacturers began putting smaller stability times on their labels/certificates to get one to purchase fresh materials more often. At our company, stuff like sodium chloride, sodium sulfate, etc. had to be disposed of more frequently, and sometimes there were additional disposal costs.

Dummmm, stoooopid.....
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