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Volume 34, Issue 8
FACT: Shelf Life does NOT mean expiration date.
FACT: A standard's expiration date should never exceed one year.
FACT: A standard's expiration date and shelf life are two entirely different entities.
This article provides you, the consumer, with the best definitions for shelf life and expiration date.
The integrity of an aqueous trace metals standard is dependent upon:
1. The chemical stability of the standard.
2. Transpiration losses of the standard.
3. The "human factor" while using the standard.
The shelf life of aqueous trace metals standards is dependent upon numbers 1 and 2 above. Shelf Life is the amount of time that a properly packaged and stored standard will last without undergoing chemical or physical changes, remaining within the specified uncertainty. A change greater than that uncertainty (±0.5% relative for our standards) means the standard has gone over (passed) its shelf life.
Inorganic Ventures manufactures single-element standards to be chemically stable indefinitely. Our chemists have been checking and testing standards for more than 25 years. Inorganic Ventures can state with certainty that there are no chemical stability problems that have not been solved. Number 1 above has been eliminated in our facility.
All standards have a limited shelf life
A standard's finite shelf life is caused by transpiration (Number 2 above). The entire chemical standard industry suffers from transpiration loss. Inorganic Ventures' scientists have studied these losses over a period of several years. Figure 1 below provides a brief presentation of our transpiration data.
Our studies, performed on our 500 mL and 125 mL LDPE bottles, showed the following:
A standard's expiration date is dependent upon Fact Numbers 1, 2, and 3. Inorganic Ventures has eliminated Number 1 and greatly reduced Number 2. This leaves the "human factor" (Number 3). Unfortunately, this is the one element that simply can't be controlled.
Expiration dates should never exceed a year
The expiration date of a standard is defined as the amount of time that it should remain in use after opening. Eventually, human error will contaminate and/or greatly devalue a standard. Most federal and state regulatory agencies recommend expiration dates no longer than one (1) year. Stricter agencies require expiration dates of half that time.
When you use a standard for longer than a year, you are gambling that absolutely nothing has inadvertently affected the certified values.
Why is the "human factor" so dangerous?
Opening a bottle can cause:
To err is human. It is not intentional, but the law of averages suggests that if something can go wrong, eventually it will.