Clearing the Smoke: The Importance of Pesticide Detection in Cannabis Testing

Several methods are used today in detecting and analyzing pesticide residues in cannabis. We often generalize compounds as pesticides due to their practical use but in fact, this general category consists of compounds with a very wide range of chemical profiles. As such, it can be difficult to develop an analytical assay that works well for each compound in these long target lists. A costly, yet absolutely necessary analytical technique, is to use internal standards and surrogate compounds to control for analytical variability (quick read on internal standards and surrogates for our fellow nerds). These compounds are specially synthesized to behave exactly like the target analyte. So, when there is a fluctuation in the surrogate/internal standard paired to the target analyte we know to follow internal procedures to reanalyze and verify results. Without properly paired surrogates and internal standards a result may be artificially inflated due to an interference leading to a false positive. Many published methods in use today use <10 or even only 4 to save money in these large assays, which beg the question of accuracy and repeatability.

Gas Chromatography (GC-MS/MS): Analyzes compounds that can brought into a gaseous state for chromatographic separation and detection by mass spec. This is an old but, tried and true method of analysis. The limiting factor is long run times which can lead to a backlog in sample processing and analysis. This is particularly challenging in high-throughput environments or when rapid results are required.

Additionally, certain compounds that are thermally unstable or have high molecular weights may not be suitable for GC-MS/MS, limiting its
applicability in some types of chemical analysis. Despite these limitations, GC-MS/MS remains a highly accurate and reliable tool for
the qualitative and quantitative analysis of volatile and semi-volatile compounds.

High-Performance Liquid Chromatography with UV/PDA (HPLC-UV): Tests compounds in their liquid state and uses a UV detector. This technology is in use in some environmental applications where the pesticide concentrations are expected to be high. The detector, however, does not have the sensitivity to look at low trace analysis levels expected in cannabis. UV/PDA detectors are not a viable option in cannabis labs.

HPLC coupled with Tandem Mass Spectrometry (MS/MS): Often abbreviated LC-MS/MS, is the most robust and accurate method for analysis of pesticides in cannabis. Simply put, it works by identifying compounds based on their molecular weight, fragments them and then verifies detection by looking at the fragments unique to each compound. Within this broad technology category also exists a technology used at Nova Analytic Labs called High Resolution Mass Spectrometry; abbreviated HR-MS or QTOF-MS (fellow nerds learn more here). This even more advanced system detects extra small differences in molecular weights which is helpful in pesticide analysis due to the existence of interferents nearly identical molecular weights as the target analyte. In short, what does this mean? We are less likely to report false positives due to similar yet ultimately different compounds present in a sample. Given the complexity of cannabis samples, Nova Analytic Labs, a leader in this field, employs state-of-the-art SCIEX systems with an extremely robust internal standard and surrogate scheme to ensure accurate and precise identification of the 66 target compounds analyzed. These instruments coupled with proper sample handling, preparation and data review procedures enhance accuracy and efficiency, ensuring the residue testing meets strict regulations, especially those specific to Maine.

An important element often overlooked when assessing a laboratory’s quality and methodologies is the team and procedures that go into the analysis. It is easy to fixate on the fancy and expensive instruments but, more often than not, the expertise of the scientists running the assays and procedures in place to verify quality and data output is more important.

Training and Qualification: The laboratory professionals need to be experts in understanding the handling of cannabis samples, preparing those samples for analysis, operating lab instruments and reviewing the data that comes off those instruments. An extensive training protocol accompanied by observed competency assessments must be completed at regular intervals. At Nova, we prescribe by a method of complete immersion. This is where a Scientist is trained on all aspects of an analysis, start to finish, and not just one segment such as sample extracts while having no understanding of the data that is output at the other end. This enables our Scientists to identify any potential issues with a clarity on how it ultimately affects the result and our clients.

Data Analysis: Analytical data requires a trained eye to interpret and report results. Lab instruments do not simply print “pass” or “fail”. Delicate review and analysis of chromatography, quality control performance, equipment calibrations and maintenance procedures are required to successfully report any results. In some cases, interpretation may not be feasible and repeat analysis may be required. For such sensitive analysis such as pesticides, Nova employs a two step review process. Step 1 is considered an initial data review and is performed by the lead pesticide scientist. Step 2, or certification, is completed by the laboratory manager and requires agreement between the two individuals before data can be released to our clients.

Preventative Maintenance: Instruments are delicate. Despite their often >$500k price tag. They do not always behave as expected and monitoring programs are needed to identify instrument performance degradation before affecting client samples. Regular cleaning, replacement of consumable parts and service contacts with the instrument OEM vendor are costly yet a necessary strategy employed by the highest quality laboratories.