Roger,

To establish an expiration date for any locally prepared reagent or reagent 
mixture requires a reasonably thorough knowledge of the properties of each 
of the components that are involved--all of which would of course include 
the supplier's recommended expiration date for one or more of the 
components--but that information would NOT be the sole factor.

In practice, the above required information often is not always available. 
In such cases, one simply has to fly by one's pants (so to speak).  I 
recommend setting a brief arbitrary period of utility, say 3 (or perhaps 6) 
months from the date of preparation but in no case greater than 6 months.

Then, if the date selection is, say, 5 months, test the stuff at the end of 
4 or 4.5 months and if it is still OK, then, arbitrarily extend the 
expiration date to, say 7 months and so on.

Thus, test it again at 6.5 months and if OK extend to 8 months.  Etc.

But in no case for a standard would I use it as a standard after one year. 
And of course, in some instances, it would be necessary to store a standard 
under controlled conditions for the entire period of its valid use.

Jay Young
*************************
----- Original Message ----- 
From: "Roger Brauninger" 
To: 
Sent: Wednesday, August 12, 2009 3:58 PM
Subject: [DCHAS-L] Assigning expiration dates

>I was wondering if there is a rule of thumb for assigning expiration dates
> of working stocks, etc.  For example: An analytic method specifies that a
> given standards solution (A) is good for one year (expires a one year 
> after
> preparation).  "A" is made from a commercially prepared standard, which 
> has
> its own expiration date.  In the situation where the expiration date on 
> the
> commercial material is one month after the current date and a solution of
> "A" is made up from it, is the expiration date still one year after the 
> date
> of "A's'" preparation or much it be restricted to the expiration date of 
> the
> commercial standard. In this case one month.
>
> To add to the discussion the Code of Federal Regulations, 40CFR, Section
> 58.113, (c ) states, "Where any of the components of the test or control
> article carrier mixture has an expiration date, that date shall be clearly
> shown on the container.  If more than one component has an expiration 
> date,
> the earliest date shall be shown."
>
> This is a difficult issue to come up with a unilateral approach because we
> have seen instances where the exact same neat materials (Reference 
> Materials
> for example but it could be any chemical for that matter) which are sold 
> by
> different manufacturers have had different expiration dates assigned to
> them.  So there is variability even with the neats.  The GLP approach is
> certainly valid for a number of materials however, for example 
> radioisotopes
> but assigning an expiration date also depends on other properties of the
> materials, for example whether they react or degrade (organics for 
> example),
> or do not (most metals).  Most producers say that it is appropriate to
> re-qualify a material.   However it all boils down to having knowledge of
> the materials at hand and the purpose for which they are used.
>
> Thoughts?
>
> Roger M. Brauninger
> BioSafety Program Manager
>
> 5301 Buckeystown Pike
> Frederick, Maryland 20895
> Direct line: (301) 644-3233      Fax: (301) 662-2974
> Email: Rbrauninger**At_Symbol_Here**a2la.org
>
> www.a2la.org 
>
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