In this issue...

News from the Lab  Articles Online  Analytical Quick Tip  Joke of the Month  The Truth About Expiration Dates

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When using chemical standard solutions, be sure to screw the cap on tightly after use and do not leave the cap off the bottle for more than a few seconds. An aqueous standard solution with a loose cap will concentrate itself through transpiration by evaporation by several % in only a few weeks.

Expiration Date is the recommended amount of time that a standard should remain in use in a laboratory setting after it has been opened. Inevitably, something will go wrong with the standard due to transpiration, cross-contamination, and/or human error. Most federal and state regulatory agencies recommend expiration dates no longer than 1 year. Some require as little as 6 months.

The expiration dates of trace metals standards are dependent upon:
  • Chemical stability of the standard.
  • Transpiration losses of the standard.
  • Human error while using the standard.

Chemical stability is typically not a factor. After a year, your standard is not going to explode or precipitate out of solution. Under the right conditions, most standards are good indefinitely.

Transpiration losses cannot be prevented. All solutions transpire -- the longer the solution exists, the more concentrated it becomes over time.

Human error is really what an expiration is trying to keep to a minimum. It is uncontrollable and inevitable. A 1 year expiration date provides a standardized window of time in which the customer can safely assume that, with proper care, the standard will remain accurate. However, it remains an assumption -- there are no guarantees that the standard will remain accurate for the duration of that year.

As a manufacturer of standards, we are part of a scientific group in which dangerous marketing tactics should not be permitted. These ploys undermine the integrity of our industry -- an industry in which a single mistake can cause a chain of errors through several high-tech fields. It is irresponsible to market standards by half-truths, hiding negative results and confusing the numbers. Protect your interests as a consumer and always remember:

If it sounds too good to be true, it probably is.

The above information was taken from Expiration Facts You Should Know.

More Information:

» Shelf Life vs. Expiration Date
» Container Transpiration

Articles Online  more articles »

Calibration Curve and Standard Additions Techniques
Part ten of our ICP Operations guide covers calibration technique options for ICP measurements including calibration curve and standard additions.

Internal Standardization and Isotope Dilution
Part eleven of our ICP Operations guide is a continuation of part ten's discussion of standard additions. The topics of internal standardization and IDMS are also introduced.

Trace Metal Analysis of Air Condensate
Dr. Gaines explains why nitric acid is used to prepare air condensate samples and offers additional information on the topic.

Matrices for Soil Preparation
Dr. Gaines recommends a couple of matrices that will work well for soil preparations that involve Si.

Joke of the Month  more humor »

A neutron walks into a bar. He asks the bartender, "How much for a beer?" The bartender offers him a warm smile and says, "For you, no charge".