Alkylsilyl speciation and direct sample preparation of plant cannabinoids prior to their analysis by GC-MS

Chromatographic and Spectroscopic Analyses of Cannabinoids: A Narrative Review Focused on Cannabis Herbs and Oily Products

Cannabis sativa L. is cultivated nowadays for agricultural, industrial, and medicinal applications and also for recreational use. The latter is due to the presence of delta-9-tetrahydrocannabinol, a psychoactive substance. Recreational cannabis policies vary between different countries, which has led to the lack of a clearly defined legal context for cannabis and also a diversity of products derived from or containing cannabis on the (il)legal market. These cannabis-derived products have regained attention, notably because of their cannabinoid content. This review aims to assess and present analytical methods developed to analyze phytocannabinoids with spectroscopic and chromatographic techniques in specific cannabis matrices: herbs and oily products. Published papers from 2018-November 2024 were searched for with precise criteria, analyzed, and summarized. In the studies, liquid and gas chromatographic techniques (>70% reviewed papers) were the most used and have been widely applied using similar methods, and most papers were focused on cannabis herbs (>75%). Techniques were also compared and future challenges were identified. A comparison of different specificities of chromatographic and spectroscopic techniques discussed in this current review has also been established and summarized.

Development and Validation of a GC-FID Method for the Quantitation of 20 Different Acidic and Neutral Cannabinoids

For decades, Cannabis sativa had been illegal to sell or consume around the world, including in the United States. However, in light of the recent 2018 Farm Bill and the legalization of hemp across the US, various cannabis preparations have flooded the market, making it essential to be able to quantitate the levels of the different acidic and neutral cannabinoids in C. sativa and to have a complete cannabinoid profile of the different chemovars of the cannabis plant. A GC-FID method was developed and validated for the analysis of 20 acidic and neutral cannabinoids as trimethylsilyl (TMS) derivatives. The analyzed cannabinoids include cannabidivarinic acid (CBDVA), cannabidiolic acid (CBDA), cannabinolic acid (CBNA), cannabielsoic acid (CBEA), cannabicyclolic acid (CBLA), cannabichromenic acid (CBCA), trans-Δ⁹-tetrahydrocannabivarinic acid (Δ⁹-THCVA), trans-Δ⁹-tetrahydrocannabinolic acid A (Δ⁹-THCAA), cannabigerolic acid (CBGA), cannabidiol (CBD), cannabicyclol (CBL), cannabidivarin (CBDV), trans-Δ⁹-tetrahydrocannabivarin (THCV), cannabichromene (CBC), trans-Δ⁸-tetrahydrocannabinol (Δ⁸-THC), trans-Δ⁹-tetrahydrocannabinol (Δ⁹-THC), cannabigerol (CBG), cannabinol (CBN), cannabicitran (CBT), and cannabielsoin (CBE). The method limit of detection (LOD) was as low as 0.1 µg/mL, while the limit of quantitation ranged from 0.25 µg/mL to 0.5 µg/mL. The precision (%RSD) was < 10%, while trueness ranged from 90 - 107%. The developed method is simple, accurate, and sensitive for the quantitation of all 20 acidic and neutral cannabinoids. Finally, the proposed method was successfully applied to the quantitation of the cannabinoids in different cannabis chemovars grown at the University of Mississippi.

Oleamide as analyte protectant in GC analysis of THC and its metabolites in blood

Methods for the analysis of cannabinoids in bio-matrices are continually being developed, to achieve a proper sensitivity required for their detection and accuracy in their quantification. The presented paper shows that the analytical sensitivity of GC-MS to THC and its metabolites in blood samples can be significantly increase by oleamide (OLA) addition to the examined sample, which evokes the matrix effect of transient character. The magnitude of signal increment resulting from oleamide presence in the examined sample is the greatest for THC metabolites and depends on oleamide concentration in the examined sample. The use of transient matrix effect to increase the sensitivity of the analysis can be applied not only in QuEChERS procedure, which is applied in the described experiments, but also in other blood sample preparation methods. Evoking the transient matrix effect by means of OLA in the experimental analytical quantitation of THC and its metabolites in blood allowed to lower limit of detection (LOD) approximately by 20.5%, 87.6% and 90.1% in the case of THC, THC-OH and THC-COOH, respectively.

Cannabinoid Profile in Cannabis sativa L. Samples by Means of LC-MRM/IDA/EPI Analysis: A New Approach for Cultivar Classification

A new multitarget screening procedure for 36 cannabinoids in 12 Cannabis sativa L. cultivars (hemp) was developed using multiple reaction monitoring (MRM) coupled with an enhanced product ion (EPI) scan in an information-dependent acquisition (IDA) experiment, which can be performed by means of high-performance liquid chromatography-mass spectrometry (HPLC-MS)/MS analysis. The MRM-IDA-EPI experiment was used for the analysis of hemp samples and the identification of the compounds of interest. It was performed through the comparison of EPI spectra with literature data and with the in-house library. The results, processed by multivariate statistical analysis, showed an accurate classification of the 12 C. sativa cultivars, emphasizing the synergic contribution of the new cannabinoids recently discovered and showing how the traditional classification based on a common cannabinoid is limiting.

Analytical Techniques for Phytocannabinoid Profiling of Cannabis and Cannabis-Based Products-A Comprehensive Review

Cannabis is gaining increasing attention due to the high pharmacological potential and updated legislation authorizing multiple uses. The development of time- and cost-efficient analytical methods is of crucial importance for phytocannabinoid profiling. This review aims to capture the versatility of analytical methods for phytocannabinoid profiling of cannabis and cannabis-based products in the past four decades (1980-2021). The thorough overview of more than 220 scientific papers reporting different analytical techniques for phytocannabinoid profiling points out their respective advantages and drawbacks in terms of their complexity, duration, selectivity, sensitivity and robustness for their specific application, along with the most widely used sample preparation strategies. In particular, chromatographic and spectroscopic methods, are presented and discussed. Acquired knowledge of phytocannabinoid profile became extremely relevant and further enhanced chemotaxonomic classification, cultivation set-ups examination, association of medical and adverse health effects with potency and/or interplay of certain phytocannabinoids and other active constituents, quality control (QC), and stability studies, as well as development and harmonization of global quality standards. Further improvement in phytocannabinoid profiling should be focused on untargeted analysis using orthogonal analytical methods, which, joined with cheminformatics approaches for compound identification and MSLs, would lead to the identification of a multitude of new phytocannabinoids.

Recent applications of mass spectrometry for the characterization of cannabis and hemp phytocannabinoids: From targeted to untargeted analysis

This review is a collection of recent applications of mass spectrometry studies for the characterization of phytocannabinoids in cannabis and hemp plant material and related products. The focus is mostly on recent applications using mass spectrometry as detector, in hyphenation to typical separation techniques (i.e., liquid chromatography or gas chromatography), but also with less common couplings or by simple direct analysis. The papers are described starting from the most common approach for targeted quantitative analysis, with applications using low-resolution mass spectrometry equipment, but also with the introduction of high-resolution mass analyzers as the detectors. This reflects a common trend in this field, and introduces the most recent applications using high-resolution mass spectrometry for untargeted analysis. The different approaches used for untargeted analysis are then described, from simple retrospective analysis of compounds without pure standards, through untargeted metabolomics strategies, and suspect screening methods, which are the ones currently allowing to achieve the most detailed qualitative characterization of the entire phytocannabinoid composition, including minor compounds which are usually overlooked in targeted studies and in potency evaluation. These approaches also represent powerful strategies to answer questions on biological and pharmacological activity of cannabis, and provide a sound technology for improved classification of cannabis varieties. Finally, open challenges are discussed for future directions in the detailed study of complex phytocannabinoid mixtures.

Improving the sensitivity of estimating CBD and other xenobiotics in plasma samples: Oleamide-induced transient matrix effect

The paper discusses the matrix effect evoked by oleamide (OLA), a compound frequently found in samples processed and/or stored in lab polypropylene vials or disposable syringes. In the case of many substances a higher response for their samples containing OLA than for net solutions is observed. The analyte signal gain resulting from OLA presence in the examined sample depends on the ratio of OLA concentration to analyte concentration. A characteristic feature of the matrix effect evoked by oleamide is its short duration, which makes the chromatographic data (retention value and signal magnitude of examined compound) repeatable and reproducible. The identified "transient matrix effect" may significantly increase the sensitivity of many analytical procedures employing GC. Evoking the transient matrix effect by means of OLA in the experimental analytical quantitation of cannabidiol in plasma allowed to lower its limit of detection (LOD) by more than 50 %.

Direct sample preparation and simultaneous perfluoroacylation - Trimethylsilylation of biogenic monoamines along with their acidic metabolites for a single step analysis by GC-MS

The GC-MS quantification of biogenic monoamines (BMAs), together with their acidic metabolites (ACMEs), in a single step, is presented here for the first time. This novel principle is based on the exceptional reactivity of the hexamethyldisilazane (HMDS) and perfluorocarboxylic acid (PFCA) couples [1,2], resulting in the simultaneous trimethylsilylation and acylation of BMAs and ACMEs. For this basic study, tyramine (TYR), 3-methoxytyramine (3-MeTYR), dopamine (DA), epinephrine (EP), normetanephrine (NORMNE), norepinephrine (NOREP), tryptamine (T), 3,4-dihydroxyphenylalanine (L-DOPA), 5-methoxytryptamine (5-MeT), serotonin (ST), and their ACMEs, such as homovanillic acid (HVA), vanillylmandelic acid (VMA), and 5-hydroxyindoleacetic acid (5-HIAA) were selected. These three ACMEs were derived from 3-MeTYR, NORMNE and ST, respectively. The mass fragmentation properties of the fully derivatized products proved to be of stoichiometric distribution. Informative high masses were obtained: such as the molecular ions [M]⁺⁼ and/or their [M-CH3]⁺ alternatives. The exceptions were EP and NOREP which decomposed to the same specific, abundant mass of m/z 355 representing the C₇H₃-tri-OTMS ions formed by the loss of their nitrogen-containing moieties. The general rule of this new principle was confirmed by using trifluoroacetic acid (TFA), pentafluoropropionic acid (PFPA), or heptafluorobutyric acid (HFBA) with HMDS in parallel tests. In all three cases, derivatives of close retention properties in a stoichiometric manner were obtained. On the basis of the optimum separation characteristics between the BMA-ACME pairs, the HMDS & PFPA couple was preferred as the reagent of choice. Method validation was carried out, both with model solutions and in the presence of the urine matrices (without any preliminary extraction). Analytical performance characteristics for the model solutions like repeatability (RSD% 3.88-6.4), linearity (R² 0.991-0.999) and limit of quantitation (LOQ 8.8-103 ng/mL) were determined. Analytical performance characteristics for urine matrices were calculated by using the standard addition method applying the urine of a healthy volunteer and also analyzing urines of patients diagnosed with neurological diseases.

Gas chromatographic analysis of naturally occurring cannabinoids: A review of literature published during the past decade

INTRODUCTION

Cannabinoids are organic compounds, natural or synthetic, that bind to the cannabinoid receptors and have similar pharmacological properties as produced by the cannabis plant, Cannabis sativa. Gas chromatography (GC), e.g. gas chromatography mass spectrometry (GC-MS), is a popular analytical tool that has been used extensively to analyse cannabinoids in various matrices.

OBJECTIVE

To review published literature on the use of various GC-based analytical methods for the analysis of naturally occurring cannabinoids published during the past decade.

METHODOLOGY

A comprehensive literature search was performed utilising several databases, like Web of Knowledge, PubMed and Google Scholar, and other relevant published materials including published books. The keywords used, in various combinations, with cannabinoids being present in all combinations, in the search were cannabinoids, Cannabis sativa, marijuana, analysis, GC, quantitative, qualitative and quality control.

RESULTS

During the past decade, several GC-based methods for the analysis of cannabinoids have been reported. While simple one-dimensional (1D) GC-MS and GC-FID (flame ionisation detector) methods were found to be quite common in cannabinoids analysis, two-dimensional (2D) GC-MS as well as GC-MS/MS also were popular because of their ability to provide more useful data for identification and quantification of cannabinoids in various matrices. Some degree of automation in sample preparation, and applications of mathematical and computational models for optimisation of different protocols were observed, and pre-analyses included various derivatisation techniques, and environmentally friendly extraction protocols.

CONCLUSIONS

GC-based analysis of naturally occurring cannabinoids, especially using GC-MS, has dominated the cannabinoids analysis in the last decade; new derivatisation methods, new ionisation methods, and mathematical models for method optimisation have been introduced.

MASS SPECTROMETRIC FRAGMENTATION OF TRIMETHYLSILYL AND RELATED ALKYLSILYL DERIVATIVES

This review describes the mass spectral fragmentation of trimethylsilyl (TMS) and related alkylsilyl derivatives used for preparing samples for analysis, mainly by combined gas chromatography and mass spectrometry (GC/MS). The review is divided into three sections. The first section is concerned with the TMS derivatives themselves and describes fragmentation of derivatized alcohols, thiols, amines, ketones, carboxylic acids and bifunctional compounds such as hydroxy- and amino-acids, halo acids and hydroxy ethers. More complex compounds such as glycerides, sphingolipids, carbohydrates, organic phosphates, phosphonates, steroids, vitamin D, cannabinoids, and prostaglandins are discussed next. The second section describes intermolecular reactions of siliconium ions such as the TMS cation and the third section discusses other alkylsilyl derivatives. Among these latter compounds are di- and trialkyl-silyl derivatives, various substituted-alkyldimethylsilyl derivatives such as the tert-butyldimethylsilyl ethers, cyclic silyl derivatives, alkoxysilyl derivatives, and 3-pyridylmethyldimethylsilyl esters used for double bond location in fatty acid spectra. © 2019 Wiley Periodicals, Inc. Mass Spec Rev 0000:1-107, 2019.

Untargeted characterization of extracts from Cannabis sativa L. cultivars by gas and liquid chromatography coupled to mass spectrometry in high resolution mode

Elucidation of Cannabis composition is required to evaluate the potential of this plant for pharmacological uses, but also for implementation in breeding programs with agronomical purposes. The aim of the present study was to develop a method for untargeted analysis of polar and non-polar Cannabis extracts. For this purpose, extracts from 17 cultivars of Cannabis sativa L. were analyzed by gas chromatography-time-of-flight/mass spectrometry (GC-TOF/MS) and liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC-QTOF MS/MS) in high resolution mode. One hundred sixty-nine compounds were identified in the extracts by searching MS and MS/MS information. Among identified families, there were mainly cannabinoids, terpenoids, lipids and flavonoids, but also some interesting compounds such as amino and organic acids, among others. Relative contents of terpenoids and cannabinoids in the same cultivars grown in greenhouse and field were compared. Compositional differences in the profile of terpenoids and cannabinoids between both types of grown conditions were found.