Options for Analysis
We can choose between analyzing these compounds by UPLC/MS, HPLC/MS and GC/MS
Many Different Compounds of Interest
There are different cannabinoids, including THC, THCA, CBD, CBDA, CBG, CBN and CBC, each with different peaks in chromatograms.
Issues with GC/MS here
THCA and CBDA are not biologically available and need to be decarboxylated before consumption.
Mini-conclusion
We don't care for THC, but not to ensure that the quantities are under 0.3% (THC + THCA) but we need to quantify available CBD, and GC would decarboxylate the CBDA when volatilizing it. Therefore, HPLC is the better option here.
Cannabinoid Quantification
Cannabinoids, also known as phytocannabinoids, are active compounds within C. sativa. Of these compounds, the only documented psychoactive compound found in reasonable quantities is (−)-trans-Δ⁹-tetrahydrocannabinol, also known as delta-9-THC or just THC. This also comes in an acid form that is not psychoactive until decarboxylated by heating, a form known as THCA. The presence of more than 0.3% THC (THC + THCA) by dry weight classifies the Cannabis as Marijuana legally, and such levels are to be avoided at all cost when producing a CBD oil. CBD is another cannabinoid, known also as cannabidiol, with a corresponding acid form, CBDA. This is the main component in CBD oil, however, the classification of the oil as "Full Spectrum" conveys that the oil as not been altered of content and that there are various other cannabinoids present in the oil. A few of these cannabinoids include CBG, CBN, CBC, and THCV, wherein all share the property of having a carboxylated acid form as well.
Analytical Options
There are two main ways to analyze the presence of various cannabinoids in samples of cannabis and cannabis product derivatives. These two methods both utilize a coupling of mass spectroscopy with chromatography, one using a liquid phase (High-Performance Liquid Chromatography-Mass Spectroscopy, HPLC/MS) and the other using a gaseous phase (Gas Chromatography-Mass Spectroscopy, GC/MS). Each of these provides advantages and disadvantages, however, HPLC/MS is more advantageous when aiming to produce a report of the full cannabinoid profile from a sample.
GC/MS
GC/MS is a decent instrumentation choice for the quantification of cannabinoids in a sample. This is ideal for determining whether a sample has too much THC/THCA, as it provides a chromatogram of the sample. The issue in using GC/MS is that inherently GC/MS is run under a mobile gas phase. This conversion to the gas phase converts any existing, normally unavailable, acid forms of the cannabinoids to their decarboxylated counterparts. This prevents proper quantification of THC vs THCA vs CBD vs CBDA. If all that was desired was to determine, 'is this hemp?', then GC/MS would be the ideal testing instrument. However, our question is, 'is this hemp, what is its potency and what is the full cannabinoid profile?', so we will avoid using GC/MS.
HPLC/MS
This instrumentation choice provides accurate and repeatable quantification of the full profile of cannabinoids present, so long as proper certified reference materials (CRM) are being used. The use of this method is superior to GC/MS for the purpose of cannabinoid quantification due to the liquid phase. A full page detailing HPLC/MS for cannabinoid quantification, terpene quantification, and pesticide analysis has been detailed here.