The Agriculture Improvement Act, also known as the Farm Bill, was signed into law in December 2018. A major provision in the law legalizes hemp as an industrial crop. In August of 2016, USDA, DEA, and FDA published a Statement of Principles in the Federal Register (FR 53365) that defined industrial hemp as any part or derivative (including seeds) of the plant Cannabis sativa L. with a dry weight concentration of tetrahydrocannabinols not greater than 0.3% (wt/wt).
Globally, the hemp market was estimated at $3.9 billion in 2017 and the hemp seed segment is predicted to grow “at a CAGR of 17.1%” through 2025. Some of the markets affected by hemp production include nutraceuticals, food, textiles, construction materials, and personal care products. It is also anticipated that cannabidiol (a non-psychoactive cannabinoid extracted from hemp) production will grow to support the burgeoning recreational and medicinal cannabis markets in the U.S., Canada and other countries around the world.
In U.S. states and Canada where recreational or medicinal marijuana programs have been legalized, regulations have been defined to assure the safety and quality of the products sold to consumers. These regulations include analytical chemistry and biological assays to identify and quantify pesticides, mycotoxins, heavy metals, residual manufacturing solvents, terpenes, and microbial contaminates. With regards to hemp, the USDA recently released guidelines for testing of hemp. To date, the only required test from the Federal perspective is total ∆9-tetrahydrocannabinol (THC) content < 0.3% by weight. Total THC is essentially the sum of tetrahydrocannabinolic acid (THCA) and THC (Total THC = 0.877(THCA) + THC) but this may be eventually expanded to include all salts and isomers of cannabinols as noted above. Another complication: what constitutes “dry”? The CFR does not answer this.
Agilent Technologies has invested in the development and implementation of the analytical protocol, the services needed to support these assays, the required consumables, reagents, and supplies, and the training of sales and support personnel to comprehensively ensure compliance of hemp with USDA regulations.
Across the country and across the world, governments that legalize cannabis implement increasingly rigorous requirements for laboratory testing. Helping to protect patients and consumers from contaminants, these requirements involve a slew of lab tests, including quantifying the levels of microbial contaminants, pathogens, mold and heavy metals.
Cannabis and hemp have a unique ability to accumulate elements found in soil, which is why these plants can be used as effective tools for bioremediation. Because cannabis plants have the ability to absorb potentially toxic and dangerous elements found in the soil they grow in, lab testing regulations often include the requirement for heavy metals testing, such as Cadmium, Lead, Mercury, Arsenic and others.
In addition to legal cannabis markets across the country, the USDA announced the establishment of the U.S. Domestic Hemp Production Program, following the enactment of the 2018 Farm Bill, essentially legalizing hemp. This announcement comes with information for hemp testing labs, including testing and sampling guidelines. While the information available on the USDA’s website only touches on testing for THC, required to be no greater than 0.3% dry weight concentration, more testing guidelines in the future are sure to include a discussion of heavy metals testing.
In an application note produced by Agilent Technologies, Inc., the Agilent 7800 ICP-MS was used to analyze 25 elements in a variety of cannabis and hemp-derived products. The study was conducted using that Agilent 7800 ICP-MS, which includes Agilent’s proprietary High Matrix Introduction (HMI) system. The analysis was automated by using the Agilent SPS 4 autosampler.
The instrument operating conditions can be found in Table 1. In this study, the HMI dilution factor was 4x and the analytes were all acquired in the Helium collision mode. Using this methodology, the Helium collision mode consistently reduces or completely eliminates all common polyatomic interferences using kinetic energy discrimination (KED).
As a comparison, Arsenic and Selenium were also acquired via the MassHunter Software using half-mass correction, which corrects for overlaps due to doubly charged rare earth elements. This software also collects semiquantitative or screening data across the entire mass region, called Quick Scan, showing data for elements that may not be present in the original calibration standards.
SRMs and Samples
Standard reference materials (SRMs) analyzed from the National Institute of Standards and Technology (NIST) were used to verify the sample prep digestion process. Those included NIST 1547 Peach Leaves, NIST 1573a Tomato Leaves and NIST 1575 Pine Needles. NIST 1640a Natural Water was also used to verify the calibration.
Samples used in the study include cannabis flower, cannabis tablets, a cannabidiol (CBD) tincture, chewable candies and hemp-derived cream.
Calibration standards were prepared using a mix of 1% HNO3 and 0.5% HCl. Sodium, Magnesium, Potassium, Calcium and Iron were calibrated from 0.5 to 10 ppm. Mercury was calibrated from 0.05 to 2 ppb. All the other elements were calibrated from 0.5 to 100 ppb.
After weighing the samples (roughly 0.15 g of cannabis plant and between 0.3 to 0.5 g of cannabis product) into quartz vessels, 4 mL HNO3 and 1 mL HCl were added and the samples were microwave digested using the program found in Table 2.
HCI was included to ensure the stability of Mercury and Silver in solution. They diluted the digested samples in the same acid mix as the standards. SRMs were prepared using the same method to verify sample digestion and to confirm the recovery of analytes.
Four samples were prepared in triplicate and fortified with the Agilent Environmental Mix Spike solution prior to the analysis. All samples, spikes and SRMs were diluted 5x before testing to reduce the acid concentration.
The calibration curves for Arsenic, Cadmium, Lead and Mercury can be found in Figure 1 and a summary of the calibration data is in Table 3. For quality control, the SRM NIST 1645a Natural Water was used for the initial calibration verification standard. Recoveries found in Table 4 are for all the certified elements present in SRM NIST 1640a. The mean recoveries and concentration range can also be found in Table 4. All the continuing calibration solution recoveries were within 10% of the expected value.
Internal Standard Stability
Figure 2 highlights the ISTD signal stability for the sequence of 58 samples analyzed over roughly four hours. The recoveries for all samples were well within 20 % of the value in the initial calibration standard.
In Table 5, you’ll find that three SRMs were tested to verify the digestion process. The mean results for most elements agreed with the certified concentrations, however the results for Arsenic in NIST 1547 and Selenium in both NIST 1547 and 1573a did not show good agreement due to interreferences formed from the presence of doubly-charged ions
Some plant materials can contain high levels of rare earth elements, which have low second ionization potentials, so they tend to form doubly-charged ions. As the quadrupole Mass Spec separates ions based on their mass-to-charge ratio, the doubly-charged ions appear at half of their true mass. Because of that, a handful of those doubly-charged ions caused overlaps leading to bias in the results for Arsenic and Selenium in samples that have high levels of rare earth elements. Using half mass correction, the ICP-MS corrects for these interferences, which can be automatically set up in the MassHunter software. The shaded cells in Table 5 highlight the half mass corrected results for Arsenic and Selenium, demonstrating recoveries in agreement with the certified concentrations.
In Table 6, you’ll find the quantitative results for cannabis tablets and the CBD tincture. Although the concentrations of Arsenic, Cadmium, Lead and Cobalt are well below current regulations’ maximum levels, they do show up relatively high in the cannabis tablets sample. Both Lead and Cadmium also had notably higher levels in the CBD tincture as well.
A spike recovery test was utilized to check the accuracy of the method for sample analysis. The spike results are in Table 6.
Using the 7800 ICP-MS instrument and the High Matrix Introduction system, labs can routinely analyze samples that contain high and very variable matrix levels. Using the automated HMI system, labs can reduce the need to manually handle samples, which can reduce the potential for contamination during sample prep. The MassHunter Quick Scan function shows a complete analysis of the heavy metals in the sample, including data reported for elements not included in the calibration standards.
The half mass correction for Arsenic and Selenium allows a lab to accurately determine the correct concentrations. The study showed the validity of the microwave sample prep method with good recovery results for the SRMs. Using the Agilent 7800 ICP-MS in a cannabis or hemp testing lab can be an effective and efficient way to test cannabis products for heavy metals. This test can be used in various stages of the supply chain as a tool for quality controls in the cannabis and hemp markets.
Disclaimer: Agilent products and solutions are intended to be used for cannabis quality control and safety testing in laboratories where such use is permitted under state/country law.
Microbial contamination on cannabis products represents one of the most significant threats to cannabis consumers, particularly immunocompromised patients who are at risk of developing harmful and potentially fatal infections.
As a result, regulatory bodies in the United States and Canada mandate testing cannabis products for certain microbes. The two most popular methods for microbial safety testing in the cannabis industry are culture-based testing and quantitative polymerase chain reaction (qPCR).
When considering patient safety, labs should choose a method that provides an accurate account of what is living on the sample and can specifically target the most harmful microbes, regardless of the matrix.
1. The Method’s Results Must Accurately Reflect the Microbial Population on the Sample
The main objective of any microbial safety test is to give the operator an indication of the microbial population present on the sample.
Culture-based methods measure contamination by observing how many organisms grow in a given medium. However, not all microbial organisms grow at the same rate. In some cases, certain organisms will out-compete others and as a result, the population in a post-culture environment is radically different than what was on the original sample.
One study analyzed fifteen medicinal cannabis samples using two commercially available culture-based methods. To enumerate and differentiate bacteria and fungi present before and after growth on culture-based media, all samples were further subjected to next-generation sequencing (NGS) and metagenomic analyses (MA). Figure 1 illustrates MA data collected directly from plant material before and after culture on 3M petrifilm and culture-based platforms.
The results demonstrate substantial shifts in bacterial and fungal growth after culturing on the 3M petrifilm and culture-based platforms. Thus, the final composition of microbes after culturing is markedly different from the starting sample. Most concerning is the frequent identification of bacterial species in systems designed for the exclusive quantification of yeast and mold, as quantified by elevated total aerobic count (TAC) Cq values after culture in the total yeast and mold (TYM) medium. The presence of bacterial colonies on TYM growth plates or cartridges may falsely increase the rejection rate of cannabis samples for fungal contamination. These observations call into question the specificity claims of these platforms.
The Live Dead Problem
One of the common objections to using qPCR for microbial safety testing is the fact that the method does not distinguish between live and dead DNA. PCR primers and probes will amplify any DNA in the sample that matches the target sequence, regardless of viability. Critics claim that this can lead to false positives because DNA from non-viable organisms can inflate results. This is often called the Live-Dead problem. However, scientists have developed multiple solutions to this problem. Most recently, Medicinal Genomics developed the Grim Reefer Free DNA Removal Kit, which eliminates free DNA contained in a sample by simply adding an enzyme and buffer and incubating for 10 minutes. The enzyme is instantaneously inactivated when lysis buffer is added, which prevents the Grim Reefer Enzyme from eliminating DNA when the viable cells are lysed (see Figure 2).
2. Method Must Be Able to Detect Specific Harmful Species
Conversely, qPCR assays, such as the PathoSEEK, are designed to target DNA sequences that are unique to pathogenic Aspergillus species, and they can be run using standard qPCR instruments such as the Agilent AriaMx. The primers are so specific that a single DNA base difference in the sequence can determine whether binding occurs. This specificity reduces the frequency of false positives in pathogen detection, a frequent problem with culture-based cannabis testing methods.
Additionally, Medicinal Genomics has developed a multiplex assay that can detect the four pathogenic species of Aspergillus (A. flavus, A. fumigatus, A. niger, and A. terreus) in a single reaction.
3. The Method Must Work on Multiple Matrices
Marijuana infused products (MIPs) are a very diverse class of matrices that behave very differently than cannabis flowers. Gummy bears, chocolates, oils and tinctures all present different challenges to culture-based techniques as the sugars and carbohydrates can radically alter the carbon sources available for growth. To assess the impact of MIPs on colony-forming units per gram of sample (CFU/g) enumeration, The Medicinal Genomics team spiked a known amount of live E. coli into three different environments: tryptic soy broth (TSB), hemp oil and hard candy. The team then homogenized the samples, pipetted amounts from each onto 3M™ Petrifilm E. coli / Coliform Count (EC) Plates, and incubated for 96 hours. The team also placed TSB without any E. coli onto a petrifilm to serve as a control. Figures 3 and 4 show the results in 24-hour intervals.
This implies the MIPs are interfering with the reporter assay on the films or that the MIPs are antiseptic in nature.
Many MIPs use citric acid as a flavoring ingredient which may interfere with 3M reporter chemistry. In contrast, the qPCR signal from the Agilent AriaMx was constant, implying there is microbial contamination present on the films, but the colony formation or reporting is inhibited.
This is not an issue with DNA-based methods, so long as the DNA extraction method has been validated on these matrices. For example, the SenSATIVAx DNA extraction method is efficient in different matrices, DNA was spiked into various MIPs as shown in Table 1, and at different numbers of DNA copies into chocolate (Table 2). The SenSATIVAx DNA extraction kit successfully captures the varying levels of DNA, and the PathoSEEK detection assay can successfully detect that range of DNA. Table 3 demonstrates that SenSATIVAx DNA extraction can successfully lyse the cells of the microbes that may be present on cannabis for a variety of organisms spiked onto cannabis flower samples.
Back in August, Lake Superior State University (LSSU) announced the formation of a strategic partnership with Agilent Technologies to “facilitate education and research in cannabis chemistry and analysis.” The university formed the LSSU Cannabis Center of Excellence (CoE), which is sponsored by Agilent. The facility, powered by top-of-the-line Agilent instrumentation, is designed for research and education in cannabis science, according to a press release.
The LSSU Cannabis CoE will help train undergraduate students in the field of cannabis science and analytical chemistry. “The focus of the new LSSU Cannabis CoE will be training undergraduate students as job-ready chemists, experienced in multi-million-dollar instrumentation and modern techniques,” reads the press release. “Students will be using Agilent’s preeminent scientific instruments in their coursework and in faculty-mentored undergraduate research.”
The facility has over $2 million dollars of Agilent instruments including their UHPLC-MS/MS, UHPLC-TOF, GC-MS/MS, LC-DAD, GC/MS, GC-FID/ECD, ICP-MS and MP-AES. Those instruments are housed in a 2600 square-foot facility in the Crawford Hall of Science. In February earlier this year, LSSU launched the very first program for undergraduate students focused completely on cannabis chemistry. With the new facility and all the technology that comes with it, they hope to develop a leading training center for chemists in the cannabis space.
Dr. Steve Johnson, Dean of the College of Science and the Environment at LSSU, says making this kind of instrumentation available to undergraduate studies is a game changer. “The LSSU Cannabis Center of Excellence, Sponsored by Agilent was created to provide a platform for our students to be at the forefront of the cannabis analytics industry,” says Dr. Johnson. “The instrumentation available is rarely paralleled at other undergraduate institutions. The focus of the cannabis program is to provide our graduates with the analytical skills necessary to move successfully into the cannabis industry.”
Storm Shriver is the Laboratory Director at Unitech Laboratories, a cannabis testing lab in Michigan, and sounds eager to work with students in the program. “I was very excited to learn about your degree offerings as there is a definite shortage of chemists who have experience with data analysis and operation of the analytical equipment required for the analysis of cannabis,” says Shriver. “I am running into this now as I begin hiring and scouting for qualified individuals. I am definitely interested in a summer internship program with my laboratory.”
LSSU hopes the new facility and program will help lead the way for more innovation in cannabis science and research. For more information, visit LSSU.edu.
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