A review of methods for the chemical characterization of cannabis natural products.

Cannabis has garnered a great deal of new attention in the past couple of years in the United States due to the increasing instances of its legalization for recreational use and indications for medicinal benefit. Despite a growing number of laboratories focused on cannabis analysis, the separation science literature pertaining to the determination of cannabis natural products is still in its infancy despite the plant having been utilized by humans for nearly 30 000 years and it being now the most widely used drug worldwide. This is largely attributable to the restrictions associated with cannabis as it is characterized as a schedule 1 drug in the United States. Presented here are reviewed analytical methods for the determination of cannabinoids (primarily) and terpenes (secondarily), the primary natural products of interest in cannabis plants. Focus is placed foremost on analyses from plant extracts and the various instrumentation and techniques that are used, but some coverage is also given to analysis of cannabinoid metabolites found in biological fluids. The goal of this work is to provide a collection of relevant separation science information, upon which the field of cannabis analysis can continue to grow.

Determination of cannabinoids from a surrogate hops matrix using multiple reaction monitoring gas chromatography with triple quadrupole mass spectrometry.

Cannabinoids are the primary bioactive constituents of Cannabis sativa and Cannabis indica plants. In this work, gas chromatography in conjunction with triple quadrupole mass spectrometry in multiple reaction monitoring mode was explored for determination of cannabinoids from a surrogate hops matrix. Gas chromatography with mass spectrometry is a reasonable choice for the analysis of these compounds; however, such methods are susceptible to false positives for Δ9-tetrahydrocannabinol, due to decarboxylation of Δ9-tetrahydrocannabinolic acid, its acid precursor, in the hot injection port. To avoid this transformation, the carboxyl group of Δ9-tetrahydrocannabinolic acid was protected through a silylation reaction. Multiple reaction monitoring transitions for both unmodified and silylated cannabinoids were developed and the fragmentation pathways for the different species were assigned. Precision and accuracy were evaluated for cannabinoids spiked into hops at different levels. The developed methods provided good linearity (R2  > 0.99) for all the cannabinoids with a linear range from 0.15 to 20 mg/L, and with limits of detection in the orders of low- to mid-picogram on column. The recoveries for the cannabinoids were generally between 75 and 120%. Precisions (<6% coefficient of variation) were within acceptable ranges.

Identification and deconvolution of carbohydrates with gas chromatography-vacuum ultraviolet spectroscopy.

Methodology for qualitative and quantitative determination of carbohydrates with gas chromatography coupled to vacuum ultraviolet detection (GC-VUV) is presented. Saccharides have been intently studied and are commonly analyzed by gas chromatography-mass spectrometry (GC-MS), but not always effectively. This can be attributed to their high degree of structural complexity: α/ß anomers from their axial/equatorial hydroxyl group positioning at the C1-OH and flexible ring structures that lead to the open chain, five-membered ring furanose, and six-membered ring pyranose configurations. This complexity can result in convoluted chromatograms, ambiguous fragmentation patterns and, ultimately, analyte misidentification. In this study, mono-, di, and tri-saccharides were derivatized by two different methods-permethylation and oximation/pertrimethylsilylation-and analyzed by GC-VUV. These two derivatization methods were then compared for their efficiency, ease of use, and robustness. Permethylation proved to be a useful technique for the analysis of ketopentoses and pharmaceuticals soluble in dimethyl sulfoxide (DMSO), while the oximation/pertrimethylsilylation method prevailed as the more promising, overall, derivatization method. VUV spectra have been shown to be distinct and allow for efficient differentiation of isomeric species such as ketopentoses and reducing versus non-reducing sugars. In addition to identification, pharmaceutical samples containing several compounds were derivatized and analyzed for their sugar content with the GC-VUV technique to provide data for qualitative analysis.