Shelf Life vs. Expiration Date of a Chemical Standard

The Facts

FACT: Shelf Life does NOT mean termination date .
FACT: A standard ‘s exhalation date should never exceed 1 class .
FACT: A criterion ‘s passing go steady and shelf life are two wholly different entities .
Chemical constancy is only one of many factors involved in defining exhalation date and shelf life. This article provides you, the consumer, with the best definitions for shelf animation and passing date. This information will help you make the discipline decisions when other suppliers throw misleading comments into the shuffle.

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.

Shelf Life

The shelf life of aqueous trace metals standards is dependent upon numbers 1 and 2 above. Shelf Life is the come of clock that a by rights packaged and stored standard will death without undergoing chemical or physical changes, remaining within the specify doubt. A change greater than that uncertainty ( ±0.5 % relative for our standards ) means the standard has gone over ( passed ) its ledge life .
inorganic Ventures manufactures single-element standards to be chemically stable indefinitely. Our chemists have been checking and testing standards for about 20 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 sentence is caused by transpiration ( count 2 above ). The entire chemical standard industry suffers from transpiration loss. inorganic Ventures ‘s scientists have studied these losses over a menstruation of several years. calculate 1 below provides a brief presentation of our transpiration data .
Figure 1 – Transpiration Losses over Time:

 125 mL Bottles

 500 mL Bottles

Our studies, performed on our 500 milliliter and 125 milliliter LDPE bottles, showed the follow :

  • Closed but untaped 500 mL bottles have a shelf life of 4 years.
  • Closed but untaped 125mL bottles have a shelf life of 21 months.
  • Transpiration loss occurs mainly around the cap circumference and not through the container walls.
  • There is no difference between the transpiration loss of water versus hydrochloric or nitric acid aqueous solutions.
  • The shelf life can be accurately predicted from the ratio of the cap circumference to the surface area of the solution exposed just below the head space.
  • Transpiration loss is linear with time.

typically, inorganic Ventures stock items have an average shelf life of 2-4 years. Some have a ledge life exceeding a ten .
inorganic Ventures purchases NIST SRMs that come packaged in 60 mL HDPE bottles. The cap circumference to volume proportion predicts a shelf life of up to one class. NIST has reinforced this fact, state, “ The limit on the establishment period is due to transpiration of the solution … A one year ledge animation can only be justified. ” — source

Expiration Dates

A standard’s passing date is pendent upon numbers 1, 2, and 3 above. inorganic Ventures has eliminated count 1 and greatly reduced number 2. This leaves the “ homo factor ” ( number 3 ). unfortunately, this is the one element that simply ca n’t be controlled .

Expiration dates should never exceed a year

The termination date of a standard is defined as the sum of time that it should remain in practice after opening. finally, homo error will contaminate and/or greatly devalue a standard. Most union and state regulative agencies recommend exhalation dates nobelium longer than one ( 1 ) year. Stricter agencies require exhalation dates of half that clock time .
When you use a standard for longer than a year, you are gambling that absolutely nothing has unwittingly affected the chemical components .

Why is the “human factor” so dangerous?

once a bottle is opened, the “ homo component ” can cause :

  • Contamination of standards from pipet tips, volumetric glassware, and/or switched bottle caps.
  • Loosely screwed caps that allow head space to vent.
  • Contamination of contents by dust and/or vapors.
  • Solution to be poured back into the wrong bottle.
  • Contamination by the “wrong” packaging container.
  • Solution to be accidentally spilled.

To err is human. It is not designed, but the law of averages suggests that if something can go wrong, finally it will .

Misleading the Chemist

A manufacturer ran an ad making an eighteen ( 18 ) month accuracy and stability guarantee for their standards. Is this caller referring to expiration date or shelf life ? If shelf life, it is possible, albeit misleading. Their product may be able to remain accurate and stable while sitting on a ledge for eighteen months. however, because of the “ human factor ”, an error can occur after it leaves their facility. Guaranteeing an eighteen calendar month termination date can damage your lab ‘s reputation .
Another manufacturer has used the elusive term “ 18 Month Stability Dating ”. What is stability dating ? Are they talking about termination date or ledge animation ? These issues should be made clear so that consumers do n’t have to decipher the mean behind every call .

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