With another round in the books, the bi-annual Emerald Test, an Inter-Laboratory Comparison and Proficiency Test (ILC/PT) program, continues to offer an ever increasing number of cannabis laboratories the opportunity to demonstrate their competence to existing clients, potential customers, regulatory agencies and accreditation bodies. Our goal is to help establish an industry benchmark for cannabis testing while providing valuable feedback to each laboratory’s’ quality assurance system. The information summarized here reflects the efforts of the Emerald Test team, our expert Advisory Panel and laboratory participants to continue improving our methods and practices while promoting good science, industry knowledge and safe products.

Spring Test Updates
In past rounds of The Emerald Test, all badge award criteria were based on consensus mean, participant Z scores and standard deviations. To improve and simplify the award process, the Advisory Panel recommended that criteria for quantitative analyses be based on percent variation of reported values versus the reference value; the certified value reported by ISO 17043 accredited proficiency test (PT) manufacturers. All Emerald Badge awards are based on the recommendation of the ISO accredited manufacturer with guidance from the Emerald Test Advisory Panel.

Proficiency test results were reported directly to the assigned ISO accredited manufacturer as determined by the corresponding Series A or B. The majority of PTs were available in a hemp or hemp oil matrix. This was done to more closely resemble the type of sample laboratories may experience in testing a variety of cannabis-derived products. It is likely that additional matrices will be introduced in future Emerald Tests.

The Advisory Panel revisited its earlier recommendation that no badge be awarded for the initial release of a new PT. After reviewing the performance of lab participants who selected a first time PT offering the Panel determined that Emerald Badge eligibility would apply to all new PTs. Inconsistencies or concerns regarding a specific PT will continue to be addressed on a case-by-case basis.

Laboratory Participation – General
77 laboratories enrolled in the Spring Emerald Test, representing 18 states and 2 foreign countries. This is a 25% increase over Fall 2017 and the 8th consecutive round that the number of participants has increased. The total number of PT samples shipped was 314, an average of 4 PTs per lab. While Potency continues to be the most popular PT, Residual Solvents and Microbial Contaminate tests are well represented. The introduction of new PTs for Potency in Hemp Oil, STEC, Aspergillus Mold and Mycotoxins generated great interest with reported results indicating that labs have been proactive in preparing for state regulatory changes and increased consumer awareness.

Series A

Microbial Panel 1 – APC, Total Coliform, E.coli, Enterobacteriaceae and Yeast/Mold

A total of 39 labs reported results for this quantitative PT. Emerald Badges were awarded to 38 labs. The reported data was aggregated and converted to base 10 logs for statistical evaluation. Of the 175 data points, 79% were generated using plate count methods.

Microbial Panel 2 – Salmonella
This qualitative PT saw 45 laboratories report results, with 42 labs able to correctly identify the contaminated salmonella sample from the 3 sample panel. Analyses were conducted using both cultural and molecular techniques with no biases noted as a result of applied techniques.

Microbial Panel 3 – STEC
One of the new PTs introduced this round; STEC (shiga-toxin expressing E.coli) goes a step beyond the Microbial Panel 1, utilizing a qualitative sample approach to identifying a particularly nasty form of E. coli. This PT had 28 labs enroll with 26 receiving Emerald Badges and one that didn’t report results. Analyses were conducted using both cultural and molecular techniques with no biases noted for either method.

Microbial Panel 4 – Aspergillus Molds
As regulatory entities evaluate the impact on patient/consumer health and wellbeing, they are including less commonly found, but more toxic contaminants. There were 12 labs enrolled in this qualitative PT, with 11 awarded an Emerald Badge and one not reporting. Once again, the reported analyses were conducted using both cultural and molecular techniques with no biases noted for either method.

Mycotoxins in Hemp
There were 16 labs participating in this quantitative PT, another strong turnout for a first time offering. All 16 were awarded an Emerald Badge, the only 100% success rate for a PT in the Spring round. The sample was prepared using hemp plant material with several mycotoxins of a known value. The majority of participants reported results using ELISA techniques with the others utilized LCMS. No statistically significant differences were observed.

Pesticide Screening in Hemp Oil
There were 24 participants in the Pesticides PT with 19 meeting Emerald Badge criteria and 4 labs that did not report results. Even with outlier rejection, the data sets for this quantitative analysis produced significant standard deviations. Trace pesticide residue testing is an extremely challenging analysis, even for expert laboratories. It is believed that these deviations are the result of low level value assignments and some labs failure to follow the sample prep instructions provided.

Series B

Potency – Cannabinoids
For the first time the Emerald Test Spring 2018 round offered two Potency PTs, the original in Solution and a new Hemp Oil matrix. Of the 62 labs that participated in the Potency PT, 48 took the PT in solution with 47 receiving an Emerald Badge. Another 23 labs took the PT in hemp oil with 22 awarded an Emerald Badge and 9 labs took both PTs. This result reinforces the fact that laboratories are capable of measuring THC, CBD and CBN content with reasonable precision and accuracy as the matrices change.

Residual Solvents in Hemp Oil
This continues to be one of the more difficult quantitative tests for all involved. With 43 labs reporting results and 31 Emerald Badges awarded for a 72% success rate among participants. The number of analytes doubled to 18 from the Fall 2017 round. Given the challenges inherent in solvent PT development and implementation, we are encouraged by the progress made over past Emerald Tests.

Heavy Metals in Hemp Oil
Of the 12 laboratories that participated in the Heavy Metals PT, 10 met criteria to receive an Emerald Badge. Arsenic was the most challenging compound of the 4 metals found in this quantitative PT. The number of labs taking this PT has increased as new players enter the cannabis space and regulatory agencies review current testing requirements. It is anticipated that testing for heavy metals will continue to be an important factor in product quality and safety.

Terpenes in Hemp Oil
It’s significant that 21 labs participated as terpene testing is not a common regulatory requirement in most states. This is another challenging quantitative analysis that was made more difficult with the introduction of a hemp oil matrix. Emerald Badges were awarded to 11 participants, making it the PT with the lowest percentage of awards at 52%. The success rate was much higher for the more commonly identified terpenes, such as Linalool, Myrcene, Limonene and the Pinene.

There were two labs that submitted an appeal of their results for review by the Emerald Test Advisory Panel. These included two for the Terpenes PT and one for Residual Solvents. Upon review, both appeals were denied however, the Residual Solvents PT was accepted for an Emerald Badge following further review and analysis.

Like the scientific community, we strive to continuously improve the Emerald Test for the benefit of all stakeholders. The Emerald Test ILC/PT program is unique in that it is guided by an advisory panel of chemists, accreditation providers, lab owners and other industry experts to ensure the program is representative of the needs and capabilities of the industry while maintaining program integrity and objectivity. To this end we intend to continue introducing new proficiency tests while expanding the menu of matrix choices in response to laboratory requests and regulatory requirements. The next Emerald Test ILC/PT is scheduled to open for enrollment on September 12, 2018.

We value, appreciate and thank all of our partners in the cannabis testing community for your continued participation and support of the Emerald Test ILC/PT. The fact that many laboratories have been regular participants in both the Spring and Fall rounds speaks volumes about their commitment to quality assurance, regulatory compliance and consumer safety. The collegial attitude of open communication and shared experience increases our knowledge and ensures continued success for all involved.

I hope to see you at the next Emerald Conference in February 2019.

In good health & good science,


Please address all questions to:
Ken Groggel, Director
Proficiency Testing Program
Emerald Scientific
Office: (877) 567-3598  Ext. 709
Mobile: (505) 301-6707