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Pesticide Testing: Methods, Strategies & Sampling

By Charles Deibel
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Editor’s Note: The following is based on research and studies performed in their Santa Cruz Lab, with contributions from Mikhail Gadomski, Lab Manager, Ryan Maus, Technical Services Analyst, Dr. Laurie Post, Director of Food Safety & Compliance, Andy Sechler, Lab Director, Toby Astill, Senior Business Development Leader at Perkin Elmer and Charles Deibel, President of Deibel Cannabis Labs.


Pesticides represent the leading cause of batch failures in the cannabis industry. They are also the hardest tests to run in the laboratory, even one equipped with state-of-the-art equipment. The best instruments on the market are HPLC and GC dual mass spectrometer detectors, called “HPLC-qqq”, “GC-qqq,” or just triple quads.

As non-lab people, we envision a laboratory that can take a cannabis sample, inject it into a triple quad and have the machine quickly and effortlessly print out a report of pesticide values. Unfortunately, this is far from reality. The process is much more hands on and complex.In the current chemistry lab, trained analysts have to first program the triple quads to look for the pesticides of concern; in cannabis pesticide testing, this is done by programming the first of two mass spectrometers to identify a single (precursor) mass that is characteristic of the pesticide in question. For BCC requirements in California, this has to be done for all 66 pesticides, one at a time.

Next, these precursor ions are degraded into secondary chemicals called the “product” ions, also called transition ions. The second of the two mass spectrometers is used to analyze these transition ions. This process is graphed and the resulting spectrum is analyzed by trained chemists in the lab, pesticide by pesticide, for all the samples processed that day. If the lab analyzes 10 samples, that translates to 660 spectra to analyze (66 pesticides x 10 samples). When looking at the spectra for each pesticide, the analysts must compare the ratios of the precursor ions to the product ions.

Confirmation Testing

If these spectra indicate a given pesticide may be present, the chemists must then compare the ratios between the precursor and the products. If these ratios are not what is expected, then the analyst must perform confirmation testing to prove the precursor mass either is or is not the pesticide of concern. If the ratios are not what is expected, it means the molecule is similar to the pesticide in question, but may not be that pesticide. This confirmatory testing is key to producing accurate results and not failing batches when dealing with closely related chemicals. This process of analyzing spectra is done in all labs that are performing pesticide testing. In this fledgling industry, there are few published cannabis pesticide methods. 

The need for this type of confirmation testing doesn’t happen all of the time, but when it does, it will take longer than our targeted three-day turn-around time. In the picture above, one precursor mass is ionized into several product masses; but only two are large enough to be used for comparison. In this hypothetical situation, two product masses are produced for every one precursor, the expected ion abundance ratio should be less than 30%. When performing any confirmatory testing, if the ion abundance ratio is >30%, it means the original precursor molecule was not the pesticide of concern. For example, if the ion abundance ratio was 50%, then the original molecule broke down into too many parts; it was not the pesticide we were looking for. This ion abundance ratio threshold was established by FANCO, the international organization that sets guidelines for all pesticide testing.

Testing Strategies

Methodology: In this fledgling industry, there are few published cannabis pesticide methods. The identification of the precursor mass and product ions are not always published, leaving labs to research which ions should be used. This adds to the potential for differences between lab results. Once selected, labs should validate their research, through a series of experiments to ensure the correct precursor and transition (product) ions are being used in the method.

Sample Preparation: Beyond the time-consuming work that is required to develop sound pesticide methods, the extraction step is absolutely critical for credible results. If the pesticides aren’t fully extracted from the cannabis product, then the results will be lower than expected. Sample preparations are often not standardized between labs, so unless a given extraction technique is validated for accuracy, there is the possibility for differences between labs.

Getting a Representative Sample

The current California recommended amount of sample is one gram of product per batch. Batch sizes can vary greatly and it is entirely likely that two different one gram samples can have two different results for pesticides. Has the entire plant been evenly coated with exactly the same amount of pesticide onto every square inch of its leaves? No, probably not. That is why it is imperative to take a “random” sample, by taking several smaller samples from different areas of the entire batch.

Sampling Plans: We can learn a lot from the manufacturing and sampling best practices developed by the food industry through the years. If a food manufacturer is concerned with the possibility of having a bacteria pathogen, like Salmonella, in their finished product, they test the samples coming off their production lines at a statistically relevant level. This practice (theory) is called the sampling plan and it can easily be adapted to the cannabis industry. The basic premise is that the more you test, the higher your likelihood of catching a contaminate. Envision a rectangular swimming pool, but instead of water, it’s filled with jello. In this gelatinous small pool, 100 pennies are suspended at varying levels. The pennies represent the contaminates.

Is the pool homogenized? Is jello evenly represented in the entire pool? Yes. 

Is your concentrate evenly distributed in the extraction vessel? Yes. The question is, where are the pennies in that extraction vessel? The heavy metals, the microbial impurities and the pesticides should be evenly distributed in the extraction vessel but they may not be evenly represented in each sample that is collected. Unfortunately, this is the bane of the manufacturing industry and it’s the unfortunate reality in the food industry. If you take one random cup of jello, will you find the penny? Probably not. But it you take numerous 1 cup samples from random areas within the batch, you increase your chances of finding the contaminate. This is the best approach for sampling any cannabis product.

The best way to approve a batch of cannabis product is to take several random samples and composite them. But you may need to run several samples from this composite to truly understand what is in the batch. In the swimming pool example, if you take one teaspoon scoop, will you find one of the pennies? The best way to find one of the pennies is to take numerous random samples, composite them and increase the number of tests you perform at the lab. This should be done on any new vendor/cultivator you work with, in order to help establish the safety of the product.

Ask the Expert: Q&A with Steve Stadlmann on Cannabis lab Accreditation

By Aaron G. Biros
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Steve Stadlmann has an extensive background as an analytical chemist working in laboratories since the early 90’s. He is now a sales specialist at PerkinElmer, an analytical instrument manufacturer that provides instruments for cannabis testing labs, in addition to a host of other industries. With over two decades of experience working in environmental testing labs, food and beverage labs and agricultural testing labs, Stadlmann is extremely familiar with the instruments used in cannabis labs.

Steve Stadlmann, sales specialist at Perkin Elmer

In 2014, he started working in the cannabis space with TriQ, Inc., a technology solutions provider for cannabis growers, where he worked in product development on a line of nutrients. In April of 2016, he started working at Juniper Analytics, a cannabis-testing laboratory in Bend, Oregon. As laboratory director there, he created their quality manual, quality assurance plan, SOP’s and all the technical documentation for ORELAP accreditation. He developed new methodologies for cannabis testing industry for residual solvents, terpene profiles and potency analysis. He worked with PerkinElmer on pesticide methodology for the QSight™ Triple Quadrupole LC/MS/MS system and implemented operational procedures and methods for LC-UV, GCMS and LC-MS/MS, including sample prep for cannabis products.

He left Juniper Analytics about two months ago to work with PerkinElmer as a sales specialist. With extensive experience in helping get Juniper’s lab accredited, he is a wealth of knowledge on all things cannabis laboratory accreditation. PerkinElmer will be hosting a free webinar on September 12th that takes a deep dive into all things cannabis lab accreditation. Ahead of the upcoming webinar, Getting Accreditation in the Cannabis Industry, we sit down with Stadlmann to hear his observations on what instruments he recommends for accreditation, and processes and procedures to support that. Take a look at our conversation below to get a glimpse into what this webinar will discuss.

CannabisIndustryJournal: How can cannabis labs prepare for accreditation with selecting instrumentation?

Steve: Finding the appropriate instrumentation for the regulations is crucial. Ensuring the instrumentation not only has the capabilities of analyzing all the required compounds, but also able to achieve appropriate detection limit requirements. In addition, having an instrument manufacturer as a partner, that is willing and able to assist in method development, implementation and continued changes to the testing requirements at the state level (and potentially national level) is key.

Another consideration is robustness of the equipment. The instrumentation must be capable of high throughput for fast turnaround times of results. Unlike the environmental industry, the cannabis industry has consumer products with expiration dates. Clients demand quick turnaround of results to get product to market as quickly as possible and avoid sitting on inventory for any length of time.

To add to the robustness need, sample matrices in the cannabis industry can be quite challenging in relation to analytical instrumentation. Equipment that is able to handle these matrices with minimal downtime for routine service is becoming a requirement to maintain throughput needs of the industry.

CIJ: What are the most crucial procedures and practices for achieving ISO 17025 accreditation?

Steve: Development and documentation of processes and procedures following Good Laboratory Practices and procedures is essential to a successful accreditation process. Great attention must be paid to the quality objectives of the laboratory as well as associated documentation, including tracking of any errors, deviations, updates, complaints, etc.

Data integrity is a key component to any accrediting body and includes implementation and/or development of appropriate methods with support data proving acceptable results. In addition, documentation of all procedures and processes along with tracking of all steps in the process during routine laboratory work should be a priority. The ability to show a complete, documented trail of all procedures done to any sample is important in ensuring the results can be reproduced and ensuring no deviations occurred, in turn potentially causing questionable results.

Last but not least: training. Laboratory staff should be well versed in any procedures they are involved in to ensure high data quality and integrity. If any laboratory staff does not receive appropriate training in any operating procedures, the data quality becomes suspect.

CIJ: What are some of the biggest obstacles or pitfalls cannabis labs face when trying to get accredited?

Steve: Not fully preparing to meet any agency and testing regulations and requirements will cause delays in the accreditation process and potentially more work for the laboratory. From documentation to daily operations, if any aspect becomes a major finding for an auditor, additional data is usually required to prove the error has been fixed satisfactorily.

Taking the time early on to ensure all documentation, processes and procedures are adhering to any regulatory agency requirements is important for a smooth accreditation process. It is easy to overlook small details when building out the operating procedures that might be essential in the process. Again, going back to data quality, the laboratory must ensure all steps are outlined and documented to ensure high quality (reproducible) data and integrity.

A new employee should be able to come in and read a quality manual and standard operating procedure and produce equivalent data to any laboratory analyst doing the same job. With difficult or challenging operating procedures it becomes even more important that training and documentation are adhered to.


PerkinElmer’s free webinar will dive into these points and others in more detail. To learn more and sign up, click here.