Your web browser will no longer be supported by as of 30 June 2021.
To avoid any interruption in access or functionality, install a current-generation web browser now. Learn more.

I’ll Second That Standard

4 May 2022
  • Heidi White
  • Share:


Chances are, if you’ve worked in a laboratory setting for even a short period of time, you’ve heard the term second source as it relates to standards tossed around like a football in a championship game.  But what defines second source, or for that matter “source”?

Second source standards are defined by an industry or accreditation.  In addition, your client’s accreditation or specific requirements might further define second source.  As for the term “source”, there are a litany of sources:  the neat material, the manufacturer of the neat material, different lots of the neat material, the manufacturer of the standard, various lots of manufactured standards, etc.  There are as many definitions of second source standards and sources as there are crayon colors.  So where does one begin?

Two industries that are very similar in their approach to second source standards are environmental and cannabis.  Let’s start with the environmental market.

Although many believe that ISO-17025:2017 outlines the criteria for second source, the true definition in the environmental industry in the United States comes from The NELAC Institute’s (TNI) Standard.  Specifically, one sentence in Volume 1, Module 4, Section states “All initial calibrations shall be verified with a standard obtained from a second manufacturer or a separate lot prepared independently by the same manufacturer.”  In layman’s terms, second source standards are standards prepared by different manufacturers, standards prepared by the same manufacturer from different neat materials or independent lots of materials prepared by the same manufacturer (ie., manufactured on a different date and/or by a different person). 

In addition, those laboratories performing analyses for the United States Department of Defense (DoD) are subject to further regulations.  According to the DoD’s Quality System Manual for Environmental Laboratories 5.3, Volume 1, Module 4, a second source standard is defined as a standard obtained from a second manufacturer or a second lot originating from a second neat material from the same manufacturer. 

It’s no surprise that the cannabis industry has taken their cues from the environmental industry, since there are numerous cross-overs between the two industries.  Although there is no specific guidance document regarding second source standards for the cannabis industry, cannabis laboratory assessors agree the priority for second sources standards are as follows:

  • State and Country requirements trump everything.
  • If available, two different vendors for the same standard/concentration.
  • If only one vendor, two different manufactured lots with separate Homogeneity, Verification, and Stability (may have same starting material because finding two different neat sources is not always possible).
  • If only one vendor and one lot at a given time, then the lab can make two different dilutions (same concentrations, often done by different staff).

Where does that leave Restek in the quest for second source standards?  The Restek Reference Standards team routinely prepares two independent lots of stock reference materials to be used for calibration and calibration verification. Independent lots are prepared using well-characterized neat starting materials by two technicians using different NIST calibrated balances.  The two independently prepared lots are assayed, post ampulation, by statistically comparing the new lot(s) to the current or previously produced lot. 

Neat starting materials used in the manufacture of Restek’s reference standards are assayed by both chromatographic and non-chromatographic methods for identity and to assign a purity value.  Why does Restek assay neat material for identity and purity?  Our in-house analysis has shown that vendor concentrations are incorrect for approximately 5% of incoming neat starting materials, and a small number are incorrectly identified or labeled.  These errors are corrected as part of our neat starting material characterization process.  Restek’s acceptance criteria for neat starting material purity is ≥ 98% with exceptions reviewed and approved by our team of chemists.  Restek weight corrects all materials with a purity <99%.

For the convenience of our customers and their auditors, Restek’s Reference Standards certificates clearly display the product lot number, the Technician’s name, the preparation date, and the balance serial number.  Other features included are the raw material lot numbers, expiration date, storage conditions and “Certified Reference Materials” clearly displayed at the top of all reference materials that fall within our ISO 17025 and 17034 scopes of accreditation. 

But wait, there’s more.  Do you need a second source for custom reference standard or a second source from a unique raw material?  Restek has programs and experience with both. 

The next time you are audited and the assessor inquires about you second source standards, know that you’re in the know.  Show them your Restek certificate with confidence.

Related Videos

Preparing a New Reference Standard for Use

View Video

How to Store Reference Standards

View Video

Sonicating Your Reference Standard

View Video

Sign In and be the first to comment.