Two notable exceptions to Jay's wisdom:

1.  There may be regulations regarding prepared standards in certified laboratories, such as ones that perform organic or inorganic analysis for drinking water.  I would first go to the EPA Laboratory Certification Manual (now in it's 5th edition) for guidance there.  I believe it's 6 mo or a 1 year, but don't quote me on that.  I do know that auditors will give you the fish-eye for having calibration standards older than 6 months for organics standards and 1 year for inorganic standards, and may even make these a "finding" on an audit.

2.  Prepared radiological standards are usually kept until they are no longer useful because of decay problems.  Depending on original source strength, isotopic half-life and counting instrumentation, that could mean days, years or decades.

Other concerns that you need to be aware of are cross-contamination problems (i.e. sticking a pipette contaminated with another standard into the bottle) and concentration issues (i.e. leaving the cap loose).  Both of these are training issues.

-----Original Message-----
>From: "Dr. Jay A. Young" 
>Sent: Aug 13, 2009 10:04 AM
>To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
>Subject: Re: [DCHAS-L] Assigning expiration dates
>
>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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>>
>> 

Harry J. Elston, Ph.D., CIH
Principal
Midwest Chemical Safety, LLC
www.midwestchemsafety.com

Editor, Journal of Chemical Health & Safety
http://membership.acs.org/c/chas/

Nationalized health care:  All the efficiency of FEMA with all
the compassion of the IRS

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