I feel that the discussion re expiration dates has been very useful but I
should point out that expiration dates are generally a consumers guide only.
While I believe that manufacturers are anxious to have the best quality
control and to give some indications of a products useful life, there is no
way that they can be expected to provide an accurate expiration date for
many of their products. They can however usually often provide some
guidance of the keeping qualities and reactivity under certain conditions
and thus give a range. There are of course some exceptions. In general,
however there is no way that they can control for the variable conditions
of use and storage in different laboratories. I believe that someone
suggested earlier to routinely test the product against known standards and
I believe that this was very sound advice and should be carried out on a
routine basis.
As an aside I am still using some color film that theoretical expired in
January 1990. The manufacturer estimates the approximate time of storage
that this film is kept on the shelf at room temperature and assigns a
realistic date for which the results can more or less be guaranteed. During
this storage time the color properties of the film changes and the
expiration date is a realistic estimate of the time beyond which color
properties may change. I and many other individuals store film at minus 20
degrees until needed and this extends the expiration date.
Barry

At 02:25 PM 11/2/98 -0500, you wrote:
>Yes, companies do real stability tests to validate shelf life.  Shelf life
>may not always be tested from Iot to lot.  The analysis or spec results are
>given a range during stability testing which determines consistent
>stability.   Expiration and certificates of analysis are usually generated
>at time of manufacture.  There are some manufacturers who establish
>expiration from time of distribution. The standard is day of manufacture at
>which case, the certificate of analysis is also generated by the QC
>department.
>
>There are various ways companies express lot numbers.  In certain cases,
>such as monocolonal antibodies it would be best to contact each
>manufacturer for their method.
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>tylee <tylee@itis.com> on 10/30/98 08:10:32 PM
>
>To:   histonet@pathology.swmed.edu
>cc:   tylee@itis.com
>Subject:  Re: Expiration Dating
>
>
>
>
>Histonetters (including Vendors),
>
>Can anyone describe just how an expiration date is established? I suspect
>these dates are, at best, just rough estimates. Do companies do real time
>stability studies to validate the shelf life of the product formulated in
>the identical manner as it is sold? Or, for instance, is there a standard
>shelf life for IgG1s in a specific buffer at a certain concentration?
>
>What about multiple lots of antibody from the same batch of monoclonal?
>When does the clock start ticking...when the mAb is generated, or when the
>bulk batch is dispensed into a specific lot?
>
>Inquiring minds want to know.
>
>Ty Lee
>tylee@itis.com
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