What are the Working Standards Storage Condition?

Dear Forum members,

Pharmacopoeial reference Standards storage condition mention as 'Store at 2-8°C" and product Storage condition is 20-25°C.
We are qualifying a working Standard against to Reference Standard and being Stored at 20-25°C to inline with the product Storage condition. Is it acceptable? or do we need to store working standards also at 2-8°C? Most of the pharma firms following this practice only but would like to any sound reason behind of this concept.

Pulla Reddy Karnati.

Depends on what you can prove! Usually, in an ‘analytical method validation’ protocol there is a section on the stability of solutions (mobile phase, working reference standard, sample solution). While the primary standard may be required to be refridgerated the working reference standard (a much lower concentration) could be acidified and much more stable.

Regarding storage conditions of working standard or secondary standard, the Ph. Eur. indicate the following: “A secondary standard is usually established to reduce the use of the primary standard and may be used for routine quality control purposes. A secondary standard shall exhibit the same property or properties as the primary standard to which it is traceable. It shall therefore be used for the same purpose as the primary standard”.

In my opinión, secondary of working standard should be stored in the same conditions of (primary) refefence standard.