Tag Archives: laboratory

By Chris English

Determination of Toxic Metals in Cannabis

Heavy metals are common environmental contaminants often resulting from mining operations, industrial waste, automotive emissions, coal fired power plants, amount other sources. Several remediation strategies exist that are common for the reduction/elimination of metals in the environment. Phytoremediation is one method for removing metals from soil, utilizing plants to uptake metals which then bioaccumulate in the plant matter. In one study, cesium concentrations were found to be 8,000 times greater in the plant roots compared to the surrounding water in the soil. In 1998, cannabis was specifically tested at the Chernobyl nuclear disaster site for its ability to remediate the contaminated soil. These examples demonstrate that cannabis must be carefully cultivated to avoid the uptake of toxic metals. Possible sources would not only include the growing environment, but also materials such as fertilizers. Many states publish metal content in fertilizer products allowing growers to select the cleanest product for their plants. For cannabis plant material and concentrates several states have specific limits for cadmium (Cd), Lead (Pb), Arsenic (As) and Mercury (Hg), based on absolute limits in product or daily dosage by body weight.

Analytical Approaches to Metals Determination

Inductively Coupled Plasma, Ionized Argon gas stream. Photo Courtesy: Sigma via Wikimedia Commons

Flame Atomic Absorption Spectroscopy (Flame AA) and Graphite Furnace Atomic Absorption Spectroscopy (GFAA) are both techniques that determine both the identity and quantity of specific elements. For both of these techniques, the absorption in intensity of a specific light source is measured following the atomization of the sample digestate using either a flame or an electrically heated graphite tube. Reference standards are analyzed prior to the samples in order to develop a calibration that relates the concentration of each element relative to its absorbance. For these two techniques, each element is often determined individually, and the light source, most commonly a hollow cathode lamp (HLC) or electrodeless discharge lamp (EDL) are specific for each element. The two most common types of Atomic Emission Spectroscopy (AES) are; Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and ICP-Mass Spectrometry (ICP-MS). Both of these techniques use an argon plasma for atomization of the sample digestates. This argon plasma is maintained using a radio frequency generator that is capable of atomization and excitation of the majority of the elements on the periodic table. Due to the considerably higher energy of the plasma-based instruments, they are more capable than the flame or furnace based systems for measurement of a wide range of elements. Additionally, they are based on optical emission, or mass spectrometric detection, and are capable of analysis of all elements at essentially the same time.

Technique Selection

Flame AA is easy to use, inexpensive and can provide reasonable throughput for a limited number of elements. However, changes to light sources and optical method parameters are necessary when determining different metals. GFAA is also limited by similar needs to change the light sources, though it is capable of greater sensitivity for most elements as compared to flame AA. Runtimes are on the order of three minutes per element for each sample, which can result in lower laboratory throughput and greater sample digestate consumption. While the sensitivity of the absorption techniques is reasonable, the dynamic range can be more limited requiring re-analyses and dilutions to get the sample within the calibration range. ICP-OES allows the simultaneous analysis of over 70 elements in approximately a minute per sample with a much greater linear dynamic range. ICP-OES instruments cost about 2-5 times more than AA instruments. ICP-MS generally has the greatest sensitivity (sub-parts-per-trillion, for some elements) with the ability to determine over 70 elements per minute. Operator complexity, instrument expense and MS stability, as well as cost are some of the disadvantages. The US FDA has a single laboratory validated method for ICP-MS for elements in food using microwave assisted digestion, and New York State recently released a method for the analysis of metals in medical cannabis products by ICP-MS (NYS DOH LINC-250).

The use of fertilizers, and other materials, with low metal content is one step necessary to providing a safe product and maintaining customer confidence. The state-by-state cannabis regulations will continue to evolve which will require instrumentation that is flexible enough to quickly accommodate added metals to the regulatory lists, lower detection limits while adding a high level of confidence in the data.

May 18, 2017

Regulatory Overreach: Are California’s Lab Rules Too Strict?

By Aaron G. Biros

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With California moving into a more regulated market, some are concerned the state may be overregulating the market with strict, unnecessary rules. The Bureau of Marijuana Control, California’s agency in charge of regulatory oversight for the cannabis industry, released a set of proposed draft regulations for lab testing recently.

Jeffrey Raber, Ph.D, Chief Executive Officer of The Werc Shop

Those rules cover everything from sampling standard operating procedures to detection limits for pesticide analytes, which some say are absurdly strict as is. According to Jeffrey Raber, Ph.D, chief executive officer of The Werc Shop, a cannabis consulting firm located in Monrovia, CA, these rules will immediately raise prices. “The regulations are quite extensive and will undoubtedly drive the costs of patient medicine upward,” says Raber. “Regulations are not intended to be so detailed in these fashions, but are supposed to provide the floor and specific framework upon which operators can build best practices and differentiate themselves from others in a competitive market that drives prices downward.”

“Comparable guidance from other states operating today, and even federal regulations, are not nearly as specific in certain aspects,” says Raber. “While there are some very good parts to the current draft, and the bureau has certainly aimed to provide strong consumer protections, as they should, the idea of benzene even being mentioned or possibly permitted, or a completely cold transportation chain being required, and pesticide levels so low it pushes the limits of the most sophisticated and modern analytical equipment while going far past sensible EPA limits, strongly suggests there is work to be done to dial back the current position and make for far more workable and fully balanced regulations before they are fully finalized.”

It is important to note that nothing is set in stone yet. The bureau will hold four public hearings throughout the month of June for the lab testing rules. In addition to that, concerned stakeholders can send written comments through June 20^th.

Dave Egerton, vice president of technical operations at CW Analytical, a cannabis-testing lab based in Oakland, is pleased they are finally regulating the market, but definitely plans on providing some feedback to change the rules a bit. “CW Analytical applauds the state’s efforts to regulate laboratories and the cannabis industry in general,” says Egerton. “…Many aspects of the proposed regulations for labs will make for a marked shift in the way our businesses operate, but the motivation behind them is well-intended.” His sentiment is consistent with many who operate cannabis laboratories and other stakeholders who see these proposed rules as overreach.

“Unfortunately, some of the regulations as written will create undo burden upon the industry and carry a strong probability of limiting supply to medical patients,” says Egerton. “During the current review period, CA laboratories will be providing feedback on some of the details within the law in order to streamline their quality assurance goals into a more tenable document that still protects patients.” That public comment period is a crucial part of the rulemaking process, as the rules will most likely change after cannabis laboratories’ voices are heard.

May 17, 2017

The Practical Chemist

Instrumentation Used for Terpene Analysis

By Tim Herring

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Terpenes are a group of volatile, unsaturated hydrocarbons found in the essential oils of plants. They are responsible for the characteristic smells and flavors of most plants, such as conifers, citrus, as well as cannabis. Over 140 terpenes have been identified to date and these unique compounds may have medicinal properties. Caryophyllene, for example, emits a sweet, woody, clove taste and is believed to relieve inflammation and produce a neuroprotective effect through CB2 receptor activation. Limonene has a citrus scent and may possess anti-cancer, anti-bacterial, anti-fungal and anti-depression effects. Pinene is responsible for the pine aroma and acts as a bronchodilator. One theory involving terpenes is the Entourage Effect, a synergistic benefit from the combination of cannabinoids and terpenes.

Many customers ask technical service which instrumentation is best, GC or HPLC, for analysis of terpenes. Terpenes are most amenable to GC, due to their inherent volatility. HPLC is generally not recommended; since terpenes have very low UV or MS sensitivity; the cannabinoids (which are present in percent levels) will often interfere or coelute with many of the terpenes.

Figure 1: Terpene profile via headspace, courtesy of ProVerde Laboratories.

Headspace (HS), Solid Phase Microextraction of Headspace (HS-SPME) or Split/Splitless Injection (SSI) are viable techniques and have advantages and disadvantages. While SPME can be performed by either direct immersion with the sample or headspace sampling, HS-SPME is considered the most effective technique since this approach eliminates the complex oil matrix. Likewise, conventional HS also targets volatiles that include the terpenes, leaving the high molecular weight oils and cannabinoids behind (Figure 1). SSI eliminates the complexity of a HS or SPME concentrator/autosampler, however, sensitivity and column lifetime become limiting factors to high throughput, since the entire sample is introduced to the inlet and ultimately the column.

The GC capillary columns range from thicker film, mid-polarity (Rxi-624sil MS for instance) to thinner film, non-polar 100% polysiloxane-based phases, such as an Rxi-1ms. A thicker film provides the best resolution among the highly volatile, early eluting compounds, such as pinene. Heavier molecular weight compounds, such as the cannabinoids, are difficult to bake off of the mid-polarity phases. A thinner, non-polar film enables the heavier terpenes and cannabinoids to elute efficiently and produces sharp peaks. Conversely the early eluting terpenes will often coelute using a thin film column. Columns that do not contain cyano-functional groups (Rxi-624Sil MS), are more robust and have higher temperature limits and lower bleed.

For the GC detector, a Mass Spectrometer (MS) can be used, however, many of the terpenes are isobars, sharing the same ions used for identification and quantification. Selectivity is the best solution, regardless of the detector. The Flame Ionization Detector (FID) is less expensive to purchase and operate and has a greater dynamic range, though it is not as sensitive, nor selective for coeluting impurities.

By accurately and reproducibly quantifying terpenes, cannabis medicines can be better characterized and controlled. Strains, which may exhibit specific medical and psychological traits, can be identified and utilized to their potential. The lab objectives, customer expectations, state regulations, available instrumentation, and qualified lab personnel will ultimately determine how the terpenes will be analyzed.

May 10, 2017

A2LA Accredits First Cannabis Testing Laboratory in Washington State

By Aaron G. Biros

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The American Association for Laboratory Accreditation (A2LA) announced today that they just accredited the Washington State Department of Agriculture-Chemical and Hop Laboratory to ISO 17025. The laboratory, based in Yakima, WA, finished the accreditation process on May 3, 2017.

The lab was accredited to ISO/IEC 17025 – General Requirements for the Competence of Testing and Calibration Laboratories, so they are now able to test for pesticides in cannabis and other matrices, according to the press release published today. “WSDA sought this accreditation to ensure our clients can have absolute confidence in our testing methods and lab results. The information we produce drives enforcement cases and policy decisions,” says Mike Firman, manager of the WSDA Chemical and Hop Laboratory. “We want to do everything that can be done to make sure our data is reliable.”

The A2LA Cannabis Accreditation Program is essentially a set of standards for quality in testing cannabis and cannabis-based products, such as infused products, tinctures and concentrates. ISO 17025 accreditation is quickly become a desirable certification for laboratories. Many states strongly encourage or even require ISO 17025 accreditation for cannabis laboratories. California recently released a set of proposed lab testing regulations for the cannabis industry that specifically requires an ISO 17025 accreditation in order for laboratories to issue certificates of analysis.

Because each state’s requirements for laboratories testing cannabis varies so greatly, A2LA works with state regulators to craft their accreditation program to meet each state’s specific requirements. “A2LA is excited to play such an important role in the accreditation of cannabis testing laboratories and is pleased to see ISO/IEC 17025 accreditation expanding into additional states,” says A2LA General Manager Adam Gouker. “Priority must be placed on ensuring that cannabis products are tested by competent laboratories to convey confidence in the results – a cornerstone which underpins the safety to all end-users.” A2LA is currently accepting applications for cannabis laboratories working to receive accreditation. Labs that already have ISO 17025 accreditation and are in a state with legal cannabis, have the ability to expand their scope of accreditation if they are looking to get into cannabis testing.

May 10, 2017

California Releases Draft Lab Testing Regulations

By Aaron G. Biros

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Last Friday, the Bureau of Marijuana Control, the regulatory body overseeing California’s cannabis industry, released a set of proposed regulations for the lab testing market. The regulations are somewhat comprehensive, covering sampling, licensing, pesticide testing, microbiological contaminants, residual solvents, water activity and much more.

Formerly named the Bureau of Medical Cannabis Regulation under the state’s Department of Consumer Affairs, the Bureau of Marijuana Control is tasked with overseeing the development, implementation and enforcement of the regulations for the state’s cannabis industry. In their statement of reasons for the lab testing regulations, the bureau says they are designed with public health and safety at top of mind. At first glance, much of these laboratory rules seem loosely modeled off of Colorado and Oregon’s already implemented testing regulations.

The regulations lay out requirements for testing cannabis products prior to bringing them to market. That includes testing for residual solvents and processing chemicals, microbiological contaminants, mycotoxins, foreign materials, heavy metals, pesticides, homogeneity as well as potency in quantifying cannabinoids.

The microbiological impurities section lays out some testing requirements designed to prevent food-borne illness. Labs are required to test for E. coli, Salmonella and multiple species of the pathogenic Aspergillus. If a lab detects any of those contaminants, that batch of cannabis or cannabis products would then fail the test and could not be sold to consumers. A lab must report all of that information on a certificate of analysis, according to the text of the regulations.

The proposed regulations stipulate requirements for sampling, including requiring labs to develop sampling plans with standard operating procedures (SOPs) and requiring a lab-approved sampler to follow chain-of-custody protocols. The rules also propose requiring SOPs for analytical methodology. That includes some method development parameters like the list of analytes and applicable matrices. It also says all testing methods need to be validated and labs need to incorporate guidelines from the FDA’s Bacterial Analytical Manual, the U.S. Pharmacopeia and AOAC’s Official Methods of Analysis for Contaminant Testing, or other scientifically valid testing methodology.

Labs will be required to be ISO 17025-accredited in order to perform routine cannabis testing. Laboratories also need to participate in proficiency testing (PT) program “provided by an ISO 17043 accredited proficiency-test provider.” If a laboratory fails to participate in the PT program or fails to pass to receive a passing grade, that lab may be subject to disciplinary action against the lab’s license. Labs need to have corrective action plans in place if they fail to get a passing grade for any portion of the PT program.

April 19, 2017

The Practical Chemist

Accurate Detection of Residual Solvents in Cannabis Concentrates

By Chris English

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Edibles and vape pens are rapidly becoming a sizable portion of the cannabis industry as various methods of consumption popularize beyond just smoking dried flower. These products are produced using cannabis concentrates, which come in the form of oils, waxes or shatter (figure 1). Once the cannabinoids and terpenes are removed from the plant material using solvents, the solvent is evaporated leaving behind the product. Extraction solvents are difficult to remove in the low percent range so the final product is tested to ensure leftover solvents are at safe levels. While carbon dioxide and butane are most commonly used, consumer concern over other more toxic residual solvents has led to regulation of acceptable limits. For instance, in Colorado the Department of Public Health and Environment (CDPHE) updated the state’s acceptable limits of residual solvents on January 1st, 2017.

Headspace Analysis

Since the most suitable solvents are volatile, these compounds are not amenable to HPLC methods and are best suited to gas chromatography (GC) using a thick stationary phase capable of adequate retention and resolution of butanes from other target compounds. Headspace (HS) is the most common analytical technique for efficiently removing the residual solvents from the complex cannabis extract matrix. Concentrates are weighed out into a headspace vial and are dissolved in a high molecular weight solvent such as dimethylformamide (DMF) or 1,3-dimethyl-3-imidazolidinone (DMI). The sealed headspace vial is heated until a stable equilibrium between the gas phase and the liquid phase occurs inside the vial. One milliliter of gas is transferred from the vial to the gas chromatograph for analysis. Another approach is full evaporation technique (FET), which involves a small amount of sample sealed in a headspace vial creating a single-phase gas system. More work is required to validate this technique as a quantitative method.

Gas Chromatographic Detectors

The flame ionization detector (FID) is selective because it only responds to materials that ionize in an air/hydrogen flame, however, this condition covers a broad range of compounds. When an organic compound enters the flame; the large increase in ions produced is measured as a positive signal. Since the response is proportional to the number of carbon atoms introduced into the flame, an FID is considered a quantitative counter of carbon atoms burned. There are a variety of advantages to using this detector such as, ease of use, stability, and the largest linear dynamic range of the commonly available GC detectors. The FID covers a calibration of nearly 5 orders of magnitude. FIDs are inexpensive to purchase and to operate. Maintenance is generally no more complex than changing jets and ensuring proper gas flows to the detector. Because of the stability of this detector internal standards are not required and sensitivity is adequate for meeting the acceptable reporting limits. However, FID is unable to confirm compounds and identification is only based on retention time. Early eluting analytes have a higher probability of interferences from matrix (Figure 2).

Figure 2: Resolution of early eluting compounds by headspace – flame ionization detection (HS-FID). Chromatogram Courtesy of Trace Analytics.

Mass Spectrometry (MS) provides unique spectral information for accurately identifying components eluting from the capillary column. As a compound exits the column it collides with high-energy electrons destabilizing the valence shell electrons of the analyte and it is broken into structurally significant charged fragments. These fragments are separated by their mass-to-charge ratios in the analyzer to produce a spectral pattern unique to the compound. To confirm the identity of the compound the spectral fingerprint is matched to a library of known spectra. Using the spectral patterns the appropriate masses for quantification can be chosen. Compounds with higher molecular weight fragments are easier to detect and identify for instance benzene (m/z 78), toluene (m/z 91) and the xylenes (m/z 106), whereas low mass fragments such as propane (m/z 29), methanol (m/z 31) and butane (m/z 43) are more difficult and may elute with matrix that matches these ions. Several disadvantages of mass spectrometers are the cost of equipment, cost to operate and complexity. In addition, these detectors are less stable and require an internal standard and have a limited dynamic range, which can lead to compound saturation.

Regardless of your method of detection, optimized HS and GC conditions are essential to properly resolve your target analytes and achieve the required detection limits. While MS may differentiate overlapping peaks the chances of interference of low molecular weight fragments necessitates resolution of target analytes chromatographically. FID requires excellent resolution for accurate identification and quantification.

April 5, 2017

Emerald Scientific Proficiency Test Approved for Lab Accreditation & Regulatory Compliance

By Aaron G. Biros

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Emerald Scientific’s Inter-Laboratory Comparison and Proficiency Test (ILC/PT) was recently approved in Washington as an official cannabis lab PT program, according to a press release. The Emerald Test program measures the accuracy of individual labs as well as comparing their results to other labs for indicators of variability and performance improvement.

Washington requires certified cannabis labs to participate in proficiency testing and Emerald Scientific’s tests is the only approved program in 4 out of 5 of the categories: potency, pesticide, heavy metals and residual solvent analysis. The most recent round of The Emerald Test showed broad improvements in many of the testing categories.

Perry Johnson, a third-party lab accreditation service for ISO/IEC 17025 also decided that The Emerald Test “meets the audit criteria for the proficiency test participation requirement for the accreditation,’ according to the press release. The proficiency test is a key component of quality assurance, which is a major requirement for labs seeking ISO 17025 accreditation. “The Emerald Scientific PT ensures that the cannabis testing labs are performing their function to the best of their ability,” says Reggie Gaudino Ph.D., vice president of Science, Genetics and Intellectual Property at Steep Hill Labs. “Any lab that isn’t participating and exceeding the minimal passing requirements should be viewed as suspect. It’s that important.”

According to the press release, Emerald Scientific’s spring 2017 program has expanded from 5 to 6 tests. The residual solvents and pesticide analysis portions offer more comprehensive testing that previously. “The other tests include 2 microbial panels and a Potency Test, which measures 5 cannabinoids including THC, THCA, CBD, CBDA, and CBN,” says the press release. “New this spring is the Heavy Metals Test, which is offered in 2 parts, one solution for cannabis heavy metals and the other in a hemp matrix.”

More than 60 labs are expected to participate. Results will be released at the National Cannabis Industry Association’s Cannabis Business Summit and Expo on June 13, 2017. For more information please visit www.emeraldtest.com or email sales@emeraldscientific.com.

March 6, 2017

Cannabis-Specific Certified Reference Materials

By Aaron G. Biros, Don Shelly

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A certified reference material (CRM) is generally recognized as providing the highest level of traceability and accuracy to a measurement. A CRM designed specifically for cannabis testing and tailored to state-specific testing regulations could help laboratories better ensure the safety of their products.

The fact that a certificate accompanies a reference material does not qualify it as a CRM. The reference material must be produced in accordance with ISO Guide 34 specifications by an accredited manufacturer. Adam Ross, key account manager and organic specialist at LGC Standards, says accreditation is a big part of bringing legitimacy to cannabis testing. “For a laboratory to receive an ISO 17025 accreditation, they must purchase their RMs from an ISO 17025 manufacturer. The best option is to purchase an ISO Guide 34 manufactured CRM,” says Ross. “It is particularly important for testing requirements, such as potency, pesticides, etc., where quantitation is expected, to use properly certified quantitative reference materials.” LGC Standards, a 175-year-old company, is one of those manufacturers that invested the time and money to achieve ISO Guide 34 accreditation and offers a spectrum of CRMs for cannabis testing.

The major advantage to using a proper CRM is an increased level of credibility. Auditors recognize the value of using a CRM which can add to the integrity of the results produced. The regular use of certified reference standards along with proper training, methodology and instrumentation, will facilitate a result that has the least amount of uncertainty and is more defendable. “The regular use of certified reference standards will help ensure products that go to market are safe to consume,” says Ross.

With regard to potency analyses, Ross has some key insights to help a laboratory better utilize CRMs. “My advice? Don’t mix the cannabinoids; labs analyzing by GC/FID have discovered that some of the cannabinoids will co-elute. Also, they have a short shelf life when mixed together,” says Ross. “Cannabinoid analysts should use GC/MS or LC/MS for their analysis or analyze the cannabinoids individually,” says Ross.

So what happens if a cannabis lab uses non-certified reference materials? Labs might save money in the short term. CRMs are slightly more expensive than a non-certified reference material, but will increase the defensibility of a lab’s data. Using a reference material created in-house or from a non-accredited vendor can lead to less-than-accurate results. A non-certified reference material has a greater chance of being made incorrectly. The publication of incorrect data damages the credibility of the testing lab and could lead to legal action against the lab from damaged parties.

One of the major challenges for the cannabis testing industry is the variation in state-to-state regulations. Ross says that Oregon’s regulations are pretty comprehensive and that other states should look to the Oregon Environmental Laboratory Accreditation Program (ORELAP) for guidance. According to Ross, ORELAP would like to see higher quality standards with legitimate traceability. Utilizing CRMs the correct way will help laboratories achieve greater accuracy.

Here are some tips for using CRMs appropriately:

Always bring your standards to room temperature before making a dilution.
Matrix matched calibration standards provide more accurate quantitation. Prepare standards in the solvent from extracted blank matrices.
Always bracket your analytical runs with continuing calibration verification standards. Proving that your instrument remained calibrated during the run gives your data more credibility.

Analytical chemists purchase CRMs for three primary uses in the testing lab:

To calibrate the instrument that will be used to perform the testing
To confirm the instruments continuing calibration throughout the analytical process
For analytical quality control or “spikes”

Typically, labs will spike known concentrations of the analytes of interest into a control sample and regular samples with the intent of testing analytical efficiency. Recoveries of analytes from the spiked control sample tell the chemist how well the analytical method is working. The spiked samples (matrix spikes) demonstrate to what extent the sample matrix (the consumable being tested) is influencing the results of the analytical procedure.

CRMs could be described as the nexus between cannabis testing results, the human element and the instrumentation used in an analysis. By using a cannabis-specific CRM, the cannabis testing community can demonstrate tangible improvements in accuracy and legitimacy.

February 21, 2017

From The Lab

QuEChERS 101

By Danielle Mackowsky

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Sample preparation experts and analytical chemists are quick to suggest QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) to cannabis laboratories that are analyzing both flower and edible material for pesticides, mycotoxins and cannabinoid content. Besides having a quirky name, just what makes QuEChERS a good extraction technique for the complicated matrices of cannabis products? By understanding the chemistry behind the extraction and the methodology’s history, cannabis laboratories can better implement the technology and educate their workforce.

QuEChERS salt blends can be packed into mylar pouches for use with any type of centrifuge tubes

In 2003, a time when only eight states had legalized the use of medical cannabis, a group of four researchers published an article in the Journal of AOAC International that made quite the impact in the residue monitoring industry. Titled Fast and Easy Multiresidue Method Employing Acetonitrile Extraction/Partitioning and “Dispersive Solid-Phase Extraction” for the Determination of Pesticide Residues in Produce, Drs. Michael Anastassiades, Steven Lehotay, Darinka Štajnbaher and Frank Schenck demonstrate how hundreds of pesticides could be extracted from a variety of produce samples through the use of two sequential steps: an initial phase partitioning followed by an additional matrix clean up. In the paper’s conclusion, the term QuEChERS was officially coined. In the fourteen years that have followed, this article has been cited over 2800 times. Subsequent research publications have demonstrated its use in matrices beyond food products such as biological fluids, soil and dietary supplements for a plethora of analytes including phthalates, pharmaceutical compounds and most recently cannabis.

QuEChERS salts can come prepacked into centrifuge tubes

The original QuEChERS extraction method utilized a salt blend of 4 g of magnesium sulfate and 1 g of sodium chloride. A starting sample volume of 10 g and 10 mL of acetonitrile (ACN) were combined with the above-mentioned salt blend in a centrifuge tube. The second step, dispersive solid phase extraction (dSPE) cleanup, included 150 mg of magnesium sulfate and 25 mg of primary secondary amine (PSA). Subsequent extraction techniques, now known as AOAC and European QuEChERS, suggested the use of buffered salts in order to protect any base sensitive analytes that may be critical to one’s analysis. Though the pH of the extraction solvent may differ, all three methods agree that ACN should be used as the starting organic phase. ACN is capable of extracting the broadest range of analytes and is compatible with both LC-MS/MS and GC-MS systems. While ethyl acetate has also been suggested as a starting solvent, it is incompatible with LC-MS/MS and extracts a larger amount of undesirable matrix components in the final aliquot.

All laboratories, including cannabis and food safety settings, are constantly looking for ways to decrease their overhead costs, batch out the most samples possible per day, and keep their employees trained and safe. It is not a stretch to say that QuEChERS revolutionized the analytical industry and made the above goals tangible achievements. In the original publication, Anastassiades et al. established that recoveries of over 85% for pesticides residues were possible at a cost as low as $1 per ten grams of sample. Within forty minutes, up to twelve samples were fully extracted and ready to be analyzed by GC-MS, without the purchase of any specialized equipment. Most importantly, no halogenated solvents were necessary, making this an environmentally conscious concept. Due to the nature of the cannabis industry, laboratories in this field are able to decrease overall solvent usage by a greater amount than what was demonstrated in 2003. The recommended starting sample for cannabis laboratories is only one gram of flower, or a tenth of the starting volume that is commonly utilized in the food safety industry. This reduction in sample volume then leads to a reduction in acetonitrile usage and thus QuEChERS is a very green extraction methodology.

The complexity of the cannabis matrix can cause great extraction difficulties if proper techniques are not used

As with any analytical method, QuEChERS is not perfect or ideal for every laboratory setting. Challenges remain in the cannabis industry where the polarity of individual pesticides monitored in some states precludes them from being amenable to the QuEChERS approach. For cannabis laboratories looking to improve their pesticide recoveries, decrease their solvent usage and not invest their resources into additional bench top equipment, QuEChERS is an excellent technique to adopt. The commercialization of salt blends specific for cannabis flowers and edibles takes the guesswork out of which products to use. The growth of cannabis technical groups within established analytical organizations has allowed for better communication among scientists when it comes to best practices for this complicated matrix. Overall, it is definitely worth implementing the QuEChERS technique in one’s cannabis laboratory in order to streamline productivity without sacrificing your results.

February 21, 2017

The Practical Chemist

Pesticide Analysis in Cannabis and Related Products: Part 3

By Julie Kowalski

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As mentioned in Part 1, pesticides residue analysis is very challenging especially considering the complexity of cannabis and the variety of flower, concentrates and infused products. In addition, pesticides are tested at low levels typically at parts-per-billion (ppb). For example, the food safety industry often uses 10 ppb as a benchmark limit of quantification. To put that in perspective, current pesticides limits in cannabis range from 10 ppb default (Massachusetts Regulatory Limit) to a more typical range of 100 ppb to 2 ppm in other states. Current testing is also complicated by evolving regulations.

Despite these challenges, adaptation of methods used by the food safety industry have proved successful for testing pesticides in cannabis. These methods typically rely on mass spectrometric detection paired with sample preparation methods to render the sample clean enough to yield quality data.

Pesticide Analysis Methods: Sample preparation and Analytical Technique Strategy

Generally, methods can be divided into two parts; sample preparation and analytical testing where both are critical to the success of pesticide residue testing and are inextricably linked. Reliance on mass spectrometric techniques like tandem mass spectrometry and high resolution accurate mass (HRAM) mass spectrometry is attributed to the substantial sensitivity and selectivity provided. The sensitivity and selectivity achievable by the detector largely dictates the sample preparation that will be required. The more sensitive and selective the detector, the less rigorous and resource intensive sample preparation can be.

Analytical technique: Gas and Liquid Chromatography Tandem Mass Spectrometry

The workhorse approach for pesticide residue analysis involves using gas chromatography and liquid chromatography tandem mass spectrometry (MS/MS) in the ion transition mode. This ion transition mode, often referred to as multiple reaction monitoring (MRM) or selected reaction monitoring (SRM), adds the selectivity and sensitivity needed for trace level analysis. Essentially, a pesticide precursor ion is fragmented into product ions. The detector monitors the signal for a specified product ion known to have originated from the pesticide precursor ion. This allows the signal to be corrected, associated with the analyte and not with other matrix components in the sample. In addition, because only ions meeting the precursor/product ion requirements are passed to the detector with little noise, there is a benefit to the observed signal to noise ratio allowing better sensitivity than in other modes. Even though ion transitions are specific, there is the possibility a matrix interference that also demonstrates that same ion transition could result in a false positive. Multiple ion transitions for each analyte are monitored to determine an ion ratio. The ion ratio should remain consistent for a specific analyte and is used to add confidence to analyte identification.

The best choice for pesticide analysis between gas chromatography (GC) and liquid chromatography (LC) is often questioned. To perform comprehensive pesticide screening similar to the way the food safety market approaches this challenge requires both techniques. It is not uncommon for screening methods to test for several hundred pesticides that vary in physiochemical properties. It may be possible that with a smaller list of analytes, only one technique will be needed but often in order to reach the low limits for pesticide residues both GC and LC are required.

Modified QuEChERS extraction using 1.5 grams of cannabis flower. Courtesy of Julie Kowalski (Restek Corporation), Jeff Dahl (Shimadzu Scientific Instruments) and Derek Laine (Trace Analytics).

Analytical technique: Sample Preparation

Less extensive sample preparation is possible when combined with sensitive and selective detectors like MS/MS. One popular method is the QuEChERS approach. QuEChERS stands for Quick, Easy, Cheap, Effective, Rugged and Safe. It consists of a solvent extraction/salting out step followed by a cleanup using dispersive solid phase extraction. Originally designed for fruit and vegetable pesticide testing, QuEChERS has been modified and used for many other commodity types including cannabis. Although QuEChERS is a viable method, sometimes more cleanup is needed and this can be done with cartridge solid phase extraction. This cleanup functions differently and is more labor intensive, but results in a cleaner extract. A cleaner extract helps to secure quality data and is sometimes needed for difficult analyses.