Discrepancies between validated GC‐FID and UHPLC‐DAD methods for the analysis of Δ‐9‐THC and CBD in dried hemp flowers

Abstract

Herbal products for smoking containing cannabidiol (CBD) are available as "lowtetrahydrocannabinol cannabis products" in most EU countries. In Belgium, Δ9-tetrahydrocannabinol (THC) content of these products must be less than 0.2% w/w, which is also the limit for agricultural hemp. For agricultural hemp, the official and only valid method for European regulators is gas-chromatography coupled to flame ionization detector (GC-FID). There is no such method, for smoking products.Many of these herbal for smoking products are analyzed as part of their quality control and have certificate of analysis. During surveillance by official labs, discrepancies were seen between the official results and the certificate of analysis. In this study, a GC-FID method based on the European method and an ultra-high-performance liquid chromatography coupled to diode array detection (UHPLC-DAD) method were validated and applied for samples analysis in order to investigate these discrepancies.The GC-FID method shows better results for the validation parameters; notably, it has β-expectation tolerance limits within 10% with a β value of 95% while the validated UHPLC-DAD method has β-expectation tolerance limits within 15% with a β value of 90%. Furthermore, the other parameters evaluated are generally better with the GC-FID method. The statistic t test shows that the difference between both methods was significantly different for total-THC, but not significantly different for the total-CBD. The authors state that, as for agricultural hemp, the GC-FID method is to be preferred for the analysis of THC and CBD in products for smoking.

Application of gas chromatography in the analysis of phytocannabinoids: An update (2020–2023)

“…A GC-FID method was successfully employed for the detection of seven phytocannabinoids, CBC (1), CBCL (2), CBG (5), CBN (7), Δ 8 -THC (9), THC (10), and tetraydrocannabivarin (THCV, 13) from the researchers. 35,37,39,40,42,51,57,58 A solid-phase-extraction (SPE) method coupled with the GC-FID technique was utilised for the extraction and detection of CBD (3) from C. sativa. Starbons A300 was used as the stationary phase in SPE taking C. sativa extract in n-hexane to selectively adsorb the phytocannabinoids onto the surface, followed by ethanol (EtOH) to facilitate desorption at up to 93%.…”

Response to letter to the editor: “Comments on ‘discrepancies between validated GC‐FID and UHPLC‐DAD methods for the analysis of Δ‐9‐THC and CBD in dried hemp flowers’”

“…We appreciate the comments of our colleagues Tsujikawa and Iwata on our article "Discrepancies between validated GC-FID and UHPLC-DAD methods for the analysis of Δ-9-THC and CBD in dried hemp flowers". 1,2 First of all, we were aware that the article could cause some discussion, since it is a very actual topic and most authors suggested liquid chromatography (LC-UV) as the better option for this kind of analysis.…”

“…This is indeed something that was never tested during the validation of the GC-FID method, and therefore, a standard solution of CBDA of 0.2 mg/ml in methanol, corresponding to a herbal sample containing 5% of CBDA, was injected on the GC-FID and analyzed according to the method described in the original article. 2 Figure 1 shows the chromatogram of this analysis, together with a chromatogram of a real sample, found positive for Δ9-THC. As can be seen, no peak was detected at the retention time of Δ9-THC.…”

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Dear editor,We appreciate the comments of our colleagues Tsujikawa and Iwata on our article "Discrepancies between validated GC-FID and UHPLC-DAD methods for the analysis of Δ-9-THC and CBD in dried hemp flowers". 1,2 First of all, we were aware that the article could cause some discussion, since it is a very actual topic and most authors suggested liquid chromatography (LC-UV) as the better option for this kind of analysis.A little bit of context, in Belgium, we have to check each year the harvest of agricultural hemp as well as a series of herbal smoking products, claimed to contain only cannabidiol (CBD) and less than 0.2% m/m of delta-9-tetrahydrocannabinol (Δ9-THC). It is agreed upon with the justice departments that only results of gas chromatography (GC) would be taken into account in court.

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“…The latter was also observed during the analysis of the real samples in the original article. 2 The conclusion of this article 2 concerning the fact that LC-UV tends to overestimate the total-CBD and total-THC and GC-FID to underestimate is based on the objective observations obtained during the validation of both methods. During validation, spiked samples were used containing the herbal matrix, so it was exactly known what result should be obtained.…”