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IR Spectrum of 2,4-Dichlorophenol in different physical states
From The Lab

Gas Chromatography/Infrared Spectroscopy: A Tool For the Analysis of Organic Compounds in Cannabis

By John F. Schneider
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IR Spectrum of 2,4-Dichlorophenol in different physical states

Editor’s Note: The author will be teaching a 1/2 day short course on this topic at PITTCON in Philadelphia in March 2019.


The combination of gas chromatography and infrared spectroscopy (GC/IR) is a powerful tool for the characterization of compounds in complex mixtures. (1-5) Gas chromatography with mass spectroscopy detection (GC/MS) is a similar technique, but GC/MS is a destructive technique that tears apart the sample molecules during the ionization process and then these fragments are used to characterize the molecule. In GC/IR the molecules are not destroyed but the IR light produced by molecular vibrations are used to characterize the molecule. IR spectrum yields information about the whole molecule which allows the characterization of specific isomers and functional groups. GC/IR is complementary to GC/MS and the combination results in a powerful tool for the analytical chemist.

A good example of the utility of GC/IR vs GC/MS is the characterization of stereo isomers. Stereo isomers are mirror images such as a left hand and a right hand. In nature, stereo isomers are very important as one isomers will be more active then its mirror image. Stereo isomers are critical to medicinal application of cannabis and also a factor in the flavor components of cannabis.

GC/MS is good at identifying basic structure, where GC/IR can identify subtle differences in structure. GC/MS could identify a hand, GC/IR could tell you if it is a left hand or right hand. GC/MS can identify a general class of compounds, GC/IR can identify the specific isomer present.

Why GC/IR?

Gas chromatography interfaced with infrared detection (GC/IR), combines the separation ability of GC and the structural information from IR spectroscopy. GC/IR gives the analyst the ability to obtain information complementary to GC/MS. GC/IR gives the analyst the power to perform functional group detection and differentiate between similar molecular isomers that is difficult with GC/MS. Isomer specificity can be very important in flavor and medical applications.

 IR Spectrum of 2,4-Dichlorophenol in different physical states

IR Spectrum of 2,4-Dichlorophenol in different physical states

Gas chromatography with mass spectrometry detection (GC/MS) is the state-of-the-art method for the identification of unknown compounds. GC/MS, however, is not infallible and many compounds are difficult to identify with 100 % certainty. The problem with GC/MS is that it is a destructive method that tears apart a molecule. In infrared spectrometry (IR), molecular identification is based upon the IR absorptions of the whole molecule. This technique allows differentiation among isomers and yields information about functional groups and the position of such groups in a molecule. GC/IR complements the information obtained by GC/MS.

Interfaces

Initial attempts to couple GC with IR were made using high capacity GC columns and stopped flow techniques. As GC columns and IR technology advanced, the GC/IR method became more applicable. The advent of fused silica capillary GC columns and the availability of Fourier transform infrared spectrometry made GC/IR available commercially in several forms. GC/IR using a flow cell to capture the IR spectrum in real time is known as the “Light Pipe”. This is the most common form of GC/IR and the easiest to use. GC/IR can also be done by capturing or “trapping” the analytes of interest eluting from a GC and then measuring the IR spectrum. This can be done by cryogenically trapping the analyte in the solid phase. A third possibility is to trap the analyte in a matrix of inert material causing “Matrix Isolation” of the analyte followed by measuring the IR spectrum.

Infrared Spectroscopy

The physical state of the sample has a large effect upon the IR spectrum produced. Molecular interactions (especially hydrogen bonding) broadens absorption peaks. Solid and liquid samples produce IR spectra with broadened peaks that loses much of the potential information obtained in the spectra. Surrounding the sample molecule with gas molecules or in an inert matrix greatly sharpens the peaks in the spectrum, revealing more of the information and producing a “cleaner” spectrum. These spectra lend themselves better to computer searches of spectral libraries similar to the computer searching done in mass spectroscopy. IR spectral computer searching requires the standard spectra in the library be of the same physical state as the sample. So, a spectrum taken in a gaseous state should be searched against a library of spectra of standards in the gaseous state.

IR of various phases:

  • Liquid Phase – Molecular interactions broaden absorption peaks.
  • Solid Phase – Molecular interactions broaden absorption peaks.
  • Gas Phase – Lack of molecular interactions sharpen absorption peaks.
  • Matrix Isolation – Lack of molecular interactions sharpen absorption peaks.

IR Chromatograms

GC/IR yields chromatograms of infrared absorbance over time. These can be total infrared absorbance which is similar to the total ion chromatogram (TIC) in GC/MS or the infrared absorbance over a narrow band or bands analogous to selected ion chromatogram. This is a very powerful ability, because it gives the user the ability to focus on selected functional groups in a mixture of compounds.

Conclusion

Gas chromatography with infrared detection is a powerful tool for the elucidation of the structure of organic compounds in a mixture. It is complementary to GC/MS and is used to identify specific isomers and congeners of organic compounds. This method is greatly needed in the Cannabis industry to monitor the compounds that determine the flavor and the medicinal value of its products.


References

  1. GC–MS and GC–IR Analyses of the Methoxy-1-n-pentyl-3-(1-naphthoyl)-Indoles: Regioisomeric Designer Cannabinoids, Amber Thaxton-Weissenfluh, Tarek S. Belal, Jack DeRuiter, Forrest Smith, Younis Abiedalla, Logan Neel, Karim M. Abdel-Hay, and C. Randall Clark, Journal of Chromatographic Science, 56: 779-788, 2018
  2. Simultaneous Orthogonal Drug Detection Using Fully Integrated Gas Chromatography with Fourier Transform Infrared Detection and Mass Spectrometric Detection , Adam Lanzarotta, Travis Falconer, Heather McCauley, Lisa Lorenz, Douglas Albright, John Crowe, and JaCinta Batson, Applied Spectroscopy Vol. 71, 5, pp. 1050-1059, 2017
  3. High Resolution Gas Chromatography/Matrix Isolation Infrared Spectrometry, Gerald T. Reedy, Deon G. Ettinger, John F. Schneider, and Sid Bourne, Analytical Chemistry, 57: 1602-1609, 1985
  4. GC/Matrix Isolation/FTIR Applications: Analysis of PCBs, John F. Schneider, Gerald T. Reedy, and Deon G. Ettinger, Journal of Chromatographic Science, 23: 49-53, 1985
  5. A Comparison of GC/IR Interfaces: The Light Pipe Vs. Matrix Isolation, John F. Schneider, Jack C. Demirgian, and Joseph C. Stickler, Journal of Chromatographic Science, 24: 330- 335, 1986
  6. Gas Chromatography/Infrared Spectroscopy, Jean ‐ Luc Le Qu é r é , Encyclopedia of Analytical Chemistry, John Wiley & Sons, 2006

Orange Photonics Introduces Terpenes+ Module in Portable Analyzer

By Aaron G. Biros
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Last week at the National Cannabis Industry Association’s (NCIA) Cannabis Business Summit, Orange Photonics unveiled their newest product added to their suite of testing instruments for quality assurance in the field. The Terpenes+ Module for the LightLab Cannabis Analyzer, which semi-quantitatively measures terpenes, Cannabichromene (CBC) and degraded THC, adds three new chemical analyses to the six cannabinoids it already reports.

CBC, a cannabinoid typically seen in hemp and CBD-rich plants, has been linked to some potentially impactful medical applications, much like the findings regarding the benefits of CBD. The module that tests for it, along with terpenes and degraded THC, can be added to the LightLab without any changes to hardware or sample preparation.

Dylan Wilks, chief technology officer of Orange Photonics
Dylan Wilks, chief technology officer of Orange Photonics

According to Dylan Wilks, chief technology officer of Orange Photonics, this could be a particularly useful tool for distillate producers looking for extra quality controls. Cannabis distillates are some of the most prized cannabis products around, but the heat used to create them can also create undesirable compounds,” says Wilks. “Distillate producers can see potency drop more than 25% if their process isn’t optimized”. With this new Terpenes+ Module, a distillate producer could quantify degraded THC content and get an accurate reading for their QC/QA department.

We spoke with Stephanie McArdle, president of Orange Photonics, to learn more about their instruments designed for quality assurance for growers and extractors alike.

Stephanie McArdle, president of Orange Photonics
Stephanie McArdle, president of Orange Photonics

According to McArdle, this could help cultivators and processors understand and value their product when terpene-rich products are the end goal. “Rather than try to duplicate the laboratory analysis, which would require expensive equipment and difficult sample preparation, we took a different approach. We report all terpenes as a single total terpene number,” says McArdle. “The analyzer only looks for monoterpenes (some common monoterpenes are myrcene, limonene and alpha-pinene), and not sesquiterpenes (the other major group of cannabis terpenes, such as Beta- Caryophyllene and Humulene) so the analysis is semi-quantitative. What we do is measure the monoterpenes and make an assumption that the sesquiterpenes are similar to an average cannabis plant to calculate a total terpene content.” She says because roughly 80% of terpenes found in cannabis are monoterpenes, this should produce accurate results, though some exotic strains may not result in accurate terpene content using this method.

The LIghtLab analyzer on the workbench
The LIghtLab analyzer on the workbench

As growers look to make their product unique in a highly competitive market, many are looking at terpenes as a source of differentiation. There are a variety of areas where growers can target higher terpene production, McArdle says. “During production, a grower may want to select plants for growing based on terpene content, or adjust nutrient levels, lighting, etc. to maximize terpenes,” says McArdle. “During the curing process, adjusting the environmental conditions to maximize terpene content is highly desirable.” Terpenes are also beginning to get recognized for their potential medical and therapeutic values as well, notably as an essential piece in the Entourage Effect. “Ultimately, it comes down to economics – terpene rich products have a higher market value,” says McArdle. “If you’re the grower, you want to prove that your product is superior. If you’re the buyer, you want to ensure the product you buy is high quality before processing it into other products. In both cases, knowing the terpene content is critical to ensuring you’re maximizing profits.”

Orange Photonics’ LightLab operates very similarly to instruments you might find in a cannabis laboratory. Many cannabis testing labs use High Performance Liquid Chromatography (HPLC) to analyze hemp or cannabis samples. “The primary difference between LightLab and an HPLC is that we operate at lower pressures and rely on spectroscopy more heavily than a typical HPLC analysis does,” says McArdle. “Like an HPLC, LightLab pushes an extracted cannabis sample through a column. The column separates the cannabinoids in the sample by slowing down cannabinoids by different amounts based on their affinity to the column.” McArdle says this is what allows each cannabinoid to exit the column at a different time. “For example, CBD may exit the column first, then D9THC and so on,” says McArdle. “Once the column separates the cannabinoids, they are quantified using optical spectroscopy- basically we are using light to do the final quantification.”

Lauren Pahnke
From The Lab

Centrifugal Partition Chromatography Paves the Way for Safer, More Standardized Cannabidiol Drugs

By Lauren Pahnke
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Lauren Pahnke

Imagine this: you are taking medication for cancer pain. One day, it works perfectly. The next, you feel no relief. On some days, you need to take three doses just to get the same effect as one. Your doctor can’t be completely positive how much active ingredient each dose contains, so you decide for yourself how much medication to take.

Doesn’t seem safe, right? It is crucial that doctors know exactly what they are prescribing to their patients. They must know that their patients are receiving the exact same dose of medication in their prescription each time they take it, and that their medication contains only the intended ingredients.

consistency is key to creating products that are safe for consumers.In the cannabis industry, lack of certainty on these important factors is a major problem for drug manufacturers as they attempt to incorporate cannabidiol (CBD), a compound found in cannabis that has no psychoactive effects but many medical benefits, into pharmaceutical drugs.

When using these compounds as medications, purity is essential. Cannabis contains a wide variety of compounds. Delta-9 tetrahydrocannabinol (THC) is the most well-known compound and its main psychoactive one1. Safety regulations dictate that consumers know exactly what they are getting when they take a medication. For example, their CBD-based medications should not contain traces of THC.

The cannabis industry greatly needs a tool to ensure the consistent extraction and isolation of compounds. In 2017, the cannabis industry was worth nearly $10 billion, and it is expected to grow $57 billion more in the next decade2. As legalization of medical cannabis expands, interest in CBD pharmaceuticals is likely to grow.

If compounds such as CBD are going to be used in pharmaceutical drugs, consistency is key to creating products that are safe for consumers.

CBD’s Potential

CBD is a non-psychoactive compound that makes up 40 percent of cannabis extracts1. It is great for medical applications because it does not interfere with motor or psychological function. Researchers have found it particularly effective for managing cancer pain, spasticity in multiple sclerosis, and specific forms of epilepsy3.

Figure 1: The chemical structure of cannabidiol.
Figure 1: The chemical structure of cannabidiol.

Other compounds derived from cannabis, such as cannabichromene (CBC) and cannabigerol (CBG), may also be beneficial compounds with medical applications. CBC is known to block pain and inflammation, and CBG is known for its use as a potential anti-cancer agent1.

Along with these compounds that provide medical benefits, there are psychoactive compounds that are used recreationally, such as THC.

“It will definitely be an advantage to have cannabis-based medications with clearly defined and constant contents of cannabinoids,” says Kirsten Müller-Vahl, a neurologist and psychiatrist at Hannover Medical School in Germany.

Creating a Standard Through Centrifugal Partition Chromatography

To obtain purified compounds from cannabis, researchers need to use technology that will extract the compounds from the plant.

Many manufacturers use some sort of chromatography technique to isolate compounds. Two popular methods are high performance liquid chromatography (HPLC) and flash chromatography. These methods have their places in the field, but they cannot be effectively and cost-efficiently scaled to isolate compounds. Instead, HPLC and flash chromatography may be better suited as analytical tools for studying the characteristics of the plant or extract. As cannabis has more than 400 chemical entities4, compound isolation is an important application.

This method is highly effective for achieving both high purity and recovery.Although molecules such as CBD can be synthesized in the lab, many companies would rather extract the compounds directly from the plant. Synthesized molecules do not result in a completely pure compound. The result, “is still a mixture of whatever cannabinoids are coming from a particular marijuana strain, which is highly variable,” says Brian Reid, chief scientific officer of ebbu, a company in Colorado that specializes in cannabis purification.

Currently, there is only one method available to researchers that completely allows them to isolate individual compounds: centrifugal partition chromatography (CPC).

The principle of CPC is similar to other liquid chromatography methods. It separates the chemical substances as the compounds in the mobile phase flow through and differentially interact with the stationary phase.

Where CPC and standard liquid chromatography differs is the nature of the stationary phase. In traditional chromatography methods, the stationary phase is made of silica or other solid particles, and the mobile phase is made of liquid. During CPC, the stationary phase is a liquid that is spun around or centrifuged to stay in place while the other liquid (mobile phase) moves through the disc. The two liquid phases, like oil and water, don’t mix. This method is highly effective for achieving both high purity and recovery. Chemists can isolate chemical components at 99 percent or higher purity with a 95 percent recovery rate5.

“CPC is ideal for ripping a single active ingredient out of a pretty complex mixture,” says Reid. “It’s the only chromatographic technique that does that well.”

The Need for Pure Compounds

High levels of purity and isolation are necessary for cannabis to be of true value in the pharmaceutical industry. Imagine relying on a medication to decrease your seizures, and it has a different effect every time. Sometimes there may be traces of psychoactive compounds. Sometimes there are too much or too little of the compound that halts your seizures. This is not a safe practice for consumers who rely on medications.“It’s hard to do studies on things you can’t control very well.”

Researchers working with cannabis desperately need a technology that can extract compounds with high purity rates. It is hard to run a study without knowing the precise amounts of compounds used. Reid uses a Gilson CPC 1000 system at ebbu for his cannabinoid research. With this technology, he can purify cannabinoids for his research and create reliable formulations. “Now that we have this methodology dialed in we can make various formulations —whether they’re water-soluble, sublingual, inhaled, you name it —with very precise ratios of cannabinoids and precise amounts of cannabinoids at the milligram level,” says Reid.

Kyle Geary, an internist at the University of Illinois at Chicago, is currently running a placebo-controlled trial of CBD capsules for Crohn’s disease. This consistent isolation is helpful for his research, as well. “Ideally, the perfect study would use something that is 100 percent CBD,” says Geary. “It’s hard to do studies on things you can’t control very well.”

The State of the Industry

While CBD is not considered a safe drug compound under federal law in the United States6, 17 states have recently passed laws that allow people to consume CBD for medical reasons7. Half of medicinal CBD users solely use the substance for treatment, a recent survey found8. As the industry quickly grows, it is crucial that consumer safety protocol keeps pace.

In June, the US Food and Drug Administration (FDA) approved the first drug that contains a purified drug substance from cannabis, Epidiolex9. Made from CBD, it is designed to treat Dravet Syndrome and Lennox-Gastaut syndrome, two rare forms of epilepsy. FDA Commissioner Scott Gottlieb said in the news release that although the FDA will work to support the development of high-quality cannabis-based products moving forward, “We are prepared to take action when we see the illegal marketing of CBD-containing products with serious, unproven medical claims. Marketing unapproved products, with uncertain dosages and formulations can keep patients from accessing appropriate, recognized therapies to treat serious and even fatal diseases.”

The industry should be prepared to implement protocols to ensure the quality of their CBD-based products. The FDA has issued warnings in recent years that some cannabinoid products it has tested do not contain the CBD levels their makers claim, and consumers should be wary of such products10. It’s hard to know when or if the FDA will begin regulating CBD-based pharmaceuticals. However, for pharma companies serious about their reputation, there is only one isolation method that creates reliable product quality: CPC.


References:

  1. Lab Manager. (2018, January 3). Cannabinoid Chemistry Infographic. Retrieved from http://www.labmanager.com/multimedia/2017/07/cannabinoid-chemistry-infographic#.WzT2e1MvyMI
  2. BDS Analytics. (2018, February 26). NEW REPORT: Worldwide spending on legal cannabis will reach $57 billion by 2027. Retrieved from https://bdsanalytics.com/press/new-report-worldwide-spending-on-legal-cannabis-will-reach-57-billion-by-2027/
  3. National Institute on Drug Abuse. (2015, June 24). The Biology and Potential Therapeutic Effects of Cannabidiol. Retrieved from https://www.drugabuse.gov/about-nida/legislative-activities/testimony-to-congress/2016/biology-potential-therapeutic-effects-cannabidiol
  4. Atakan, Z. (2012). Cannabis, a complex plant: Different compounds and different effects on individuals. Therapeutic Advances in Psychopharmacology,2(6), 241-254. doi:10.1177/2045125312457586
  5. Gilson. (n.d.). Centrifugal Partition Chromatography (CPC) Systems. Retrieved from http://www.gilson.com/en/AI/Products/80.320#.WzVB2lMvyMI
  6. Mead, A. (2017). The legal status of cannabis (marijuana) and cannabidiol (CBD) under US law. Epilepsy & Behavior, 70, 288-291.
  7. ProCon.org. (2018, May 8). 17 States with Laws Specifically about Legal Cannabidiol (CBD) – Medical Marijuana – ProCon.org. Retrieved from https://medicalmarijuana.procon.org/view.resource.php?resourceID=006473
  8. Borchardt, D. (2017, August 03). Survey: Nearly Half Of People Who Use Cannabidiol Products Stop Taking Traditional Medicines. Retrieved from https://www.forbes.com/sites/debraborchardt/2017/08/02/people-who-use-cannabis-cbd-products-stop-taking-traditional-medicines/#43889c942817
  9. U.S. Food & Drug Administration. (2018, June 25). Press Announcements – FDA approves first drug comprised of an active ingredient derived from marijuana to treat rare, severe forms of epilepsy. Retrieved from https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm611046.htm
  10. U.S. Food & Drug Administration. (2017). Public Health Focus – Warning Letters and Test Results for Cannabidiol-Related Products. Retrieved from https://www.fda.gov/newsevents/publichealthfocus/ucm484109.htm
The Practical Chemist

Building the Foundation of Medical Cannabis Testing – Understanding the Use of Standards and Reference Materials – Part 2

By Joe Konschnik
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In the last article I referred to the analogy of the analytical reference material being a keystone of the laboratory foundation, the stone upon which all data relies. I then described the types of reference materials and their use in analytical testing in general terms. This article will describe the steps required to properly manufacture and deliver a certified reference material (CRM) along with the necessary documentation.

A CRM is an exclusive reference material that meets strict criteria defined by ISO Guide 34 and ISO/IEC 17025.  ISO is the International Organization for Standardization and IEC is the International Electrotechnical Commission. These organizations work together to set globally recognized standards. In order for a reference material to be labeled as a CRM it must 1) be made with raw or starting materials which are characterized using qualified methods and instruments, 2) be produced in an ISO-accredited lab under documented procedures, and 3) fall under the manufacturer’s scopes of accreditation. Verifying a CRM supplier has these credentials is easily done by viewing their certificates which should include their scopes of accreditation. Restek_accredit

There are many steps required to produce a CRM that meets the above three criteria.  The first step requires a review of the customer’s, or end-user’s requirements to carefully define what is to be tested, at what levels and which analytical workflow will be used.  Such information enables the producer to identify the proper compounds and solvents required to properly formulate the requested CRM.

The next step requires sourcing and acquiring the raw, or starting materials, then verifying their compatibility and stability using stability and shipping studies in accordance with ISO requirements. Next the chemical identify and purity of the raw materials must be characterized using one or more analytical techniques such as: GC-FID, HPLC, GC-ECD, GC-MS, LC-MS, refractive index and melting point. In some cases, the percent purity is changed by the producer when their testing verifies it’s different from the supplier label. All steps are of course documented.

restek_CRMThe producer’s analytical balances must be verified using NIST traceable weights and calibrated annually by an accredited third party provider to guarantee accurate measurement. CRMs must be prepared using Class A volumetric glassware, and all ampules and vials used in preparation and final packaging must be chemically treated to prevent compound degradation during storage. Next, CRMs are packaged in an appropriate container, labeled then properly stored to maintain the quality and stability until it’s ready to be shipped. All labels must include critical storage, safety and shelf life information to meet federal requirements. The label information must be properly linked to documentation commonly referred to as a certificate of analysis (COA) which describes all of the above steps and verifies the traceability and uncertainty of all measurements for each compound contained in the CRM. Restek_CRM2

My company, RESTEK, offers a variety of documentation choices to accompany each CRM. Depending on the intended use and data quality objectives specified by the end-user, which were defined way back at the first step, three options are typically offered: They include gravimetric only, qualitative which includes gravimetric, and fully quantitative which includes all three levels of documentation. The graphic to the right summarizes the three options and what they include.

It’s important to understand which level you’re purchasing especially when ordering a custom CRM from a supplier. Most stock CRMs include all three levels of documentation, but it’s important to be sure.

Understanding what must be done to produce and deliver a CRM sets it apart from other reference material types, however it’s important to understand there are some instances where CRMs are either not available, nor required and in those situations other types of reference materials are perfectly acceptable.

If you have any questions or would like more details about reference materials please contact me, Joe Konschnik at (800) 356-1688 ext. 2002 by phone, or email me at joe.konschnik@restek.com.