Featured Article
Developing new protocols to build accurate and repeatable analysis
According to the U.S. Drug Enforcement Administration Museum’s website,1 “The oldest known written record on cannabis use comes from the Chinese Emperor Shen Nung in 2727 B.C.” Over millennia, the use of this plant has experienced highs and lows: Farmers in the United States were encouraged to grow it as a source of fiber in the 17th century; it was universally illegal by the second half of the 20th century, and today is seemingly on its way back to, if not respectability, then acceptance. In March 2016, The Washington Post reported: “A new survey released today by the AP-NORC Center for Public Affairs Research finds that a record-high percentage of Americans—61%—say they support marijuana legalization.”2 So it’s little surprise that state after state is legalizing the use of this plant for either recreational or medicinal use, or both. In parallel with expanding use, analytical labs work hard to develop more accurate and reliable methods of analyzing the components of cannabis samples, and this demands the use of mass spectrometry (MS).
“Mass spectrometry is a critical tool for analysis of a wide variety of substances in cannabis, especially chemical residues such as pesticides,” says Jeff Dahl, applications scientist at Shimadzu Scientific Instrument’s (Columbia, Md.) Innovation Center. “This is because many chemical residues and pesticides could be potentially harmful, even at levels in the partsper- million range or lower.”
The way people use cannabis also impacts the needed testing. “A pesticide may be approved for use on other crops, but they aren’t typically smoked,” says Paul Winkler, marketing development manager, food and environmental, Americas at SCIEX (Framingham, Mass.). “For many pesticides, people don’t understand the toxicity of things burned or inhaled.” Consequently, most cannabis products cannot contain any pesticides. As Winkler says, “Currently, limits are zero; however, once evaluations and investigations have been conducted by the regulators, we may see the levels being around the 10 parts-per-billion level.”
A cannabis sample is also complex. “All of the different pigments, terpenes, waxes, etcetera could potentially interfere with the signal if the instrument has insufficient selectivity,” Dahl explains.
MS provides the necessary sensitivity and selectivity to analyze cannabis samples. It can be combined with liquid chromatography (LC), gas chromatography (GC) and inductively coupled plasma (ICP) separations. “LC/MS is primarily used for the quality-control detection of pesticides, whereas GC/MS is used for volatile pesticides, terpenes and residual solvents,” says Scott Kuzdzal, general manager of marketing at Shimadzu Scientific Instruments. “ICP/MS is useful for analyzing heavy metals, which typically come from the soil that the cannabis grows in.”
Cannabinoid concentrations
A cannabis sample comprises a collection of cannabinoids, including cannabidiol (CBD), tetrahydrocannabinol (THC) and others. “The concentrations of the most common cannabinoids are relatively high, so that UV detectors are adequate for potency measurements,” Kuzdzal says. “But mass spectrometers can be used to interrogate low levels of cannabinoids.”
The treatment of the sample also impacts analysis. “Overall, HPLC is preferred over GC because it applies much less heat in the testing process, allowing cannabinoids to be measured in their naturally occurring forms,” Kuzdzal says. “This means acidic—such as THCa, CBDa, etcetera— and neutral cannabinoids—such as THC, CBD, etcetera—can be differentiated in a sample.”
The trend to legalize various uses of cannabis is driving production, as seen at the Oregon Medical Marijuana Program cultivation facility. (Image courtesy of Shimadzu.)Measurement of the cannabinoid concentrations matters for quality control of products that are legal, but general analysis can also be used in criminal studies. An LC/MS study of sewage from the Greek island of Lesvos revealed 22 drugs of abuse, including forms of THC.3
Also, an LC/MS study of drivers involved in accidents in British Columbia revealed cannabis metabolites in 12.6%.4 The authors concluded: “Alcohol [use] is well known to [be a contributing] cause [in] crashes, but further research is needed to determine the impact of other drug use, including drug–alcohol and drug–drug combinations, on crash risk.”
The legal and illegal uses of cannabis can also collide. “MS is a critical tool for the forensic analysis of samples from suspected cannabis users in suspected illegal activities, such as driving under the influence of intoxicants,” says Joe Anacleto, vice president applied markets and pharma business at Bruker (Milton, Canada). “As the legalization of cannabis continues to spread, the potential incidents of drug-induced illegal activities may increase, and law-enforcement agencies will require improved tools that allow the rapid analysis of various complex samples that are cost effective, easy to use and produce results with high confidence that are defensible in a court of law.”
MS methods
The Shimadzu LCMS-8050, a triple-quadrupole LC/MS, can analyze cannabis samples for the presence of pesticides. (Image courtesy of Shimadzu.)Selection of the MS technique depends on the kind of chromatography used to separate the components of a cannabis sample. With GC and LC, respectively, the most common forms of MS are single and triple quadrupole. “Triple-quadrupole mass spectrometers are most common for pesticide analysis because they can target specific pesticides and quantitate them,” Kuzdzal says. “Single-quadrupole GC/MS instruments are useful for the analyses of terpenes and residual solvents.”
Other experts agree that various methods are used. “GC-triple quads and LC-triple quads are very common tools used for the low-level, targeted detection of cannabis and its metabolites in various matrices,” says Anacleto. “Ion trap and QTOF (quadrupole time-of-flight)-based solutions are also increasing in popularity due to their additional capabilities to screen for a much broader number of drugs of abuse with very high confidence and still be able to provide high-sensitivity quantification.”
For some studies, certain types of analysis might not work. “Lots of pesticides don’t go through GC,” says Winkler.
Still, GC/MS works well for some applications. Swiss scientists used it to study the efficacy of vaporizers to deliver cannabis for medicinal purposes.5 They found that electrically driven vaporizers “offer a promising application mode for the safe and efficient administration of medicinal cannabis.”
Speed and efficiency
As more states approve various uses of cannabis, labs and companies need faster ways to analyze samples. “Ultrafast mass spectrometry enables exceptionally fast data acquisition and polarity switching speeds,” Kuzdzal says. “This allows positive and negative analytes—including pesticides and terpenes—to be monitored in a single run, reducing the number of injections/runs in half.” He adds, “These ultrafast instruments also enable more data points to be collected across each peak, resulting in more accurate quantitation.”
Just as MS must get faster and more accurate, this technology—like most—needs to align with the growing interest in energy efficiency. “Most modern mass specs are now equipped with ‘ecology modes’ that can reduce the power consumed in analysis standby mode,” Kuzdzal says. “The new Shimadzu ICPMS-2030 has an environmentally friendly minitorch plasma unit that minimizes the energy—electricity—consumed in producing and maintaining an argon plasma.”
Developers also make systems that provide more than one benefit. The SCIEX X500R QTOF system, notes Winkler, “was engineered to be easy to use, and it’s very sensitive, down to parts per trillion.” Ease of use in this system and others depends on the software. QTOFs, says Winkler, “generate complex data, so the software is very important. … You need the computer to look for peaks and then compare them to libraries, and all of this should be integrated in the system.”
When it comes to analyzing cannabis samples, Winkler says, “the science on this is far from settled.” But, he adds, “It could start to get simpler as we move toward standardized methods of analysis.” Even now, labs produce more consistent results than they did in the past, and more robust repeatability surely lies ahead.
References
- www.deamuseum.org/ccp/cannabis/history.html
- www.apnorc.org/PDFs/Drugs/AP-NORC%20Drugs%20Report%20Topline.pdf
- Gatidou, G.; Kinyua, J. et al. Drugs of abuse and alcohol consumption among different groups of population on the Greek Island of Lesvos through sewage-based epidemiology. Science of the Total Environment 2016; doi: 10.1016/j.scitotenv.2016.04.130.
- Brubacher, J.R.; Chan, H. et al. Prevalence of alcohol and drug use in injured British Columbia drivers. BMJ Open 2016; doi: 10.1136/bmjopen- 2015-009278.
- Lanz, C.; Mattsson, J. et al. Medicinal cannabis: in vitro validation of vaporizers for the smoke-free inhalation of cannabis. PLoS One 2016; doi: 10.1371/journal.pone.0147286.
Mike May is a freelance writer and editor living in Florida. He can be reached at [email protected].