Formation of trifluoroacetic artefacts in gas chromatograph injector during Cannabidiol analysis

•Δ9-THC-TFA and Δ8-THC-TFA as a newly revealed CBD transformation products.•Formation of trifluoroacetic artefacts during CBD analysis by GC.•Accurate estimation of CBD concentration in blood/plasma by GC can be problematic. The knowledge of compounds stability in the process of sample preparation for analysis and during analysis itself helps assess the accuracy and precision of estimating their concentration in tested samples. The present paper shows that a significant amount of CBD present in the blood/plasma sample analyzed by means of GC transforms in the hot GC injector not only to 9α-hydroxyhexahydrocannabinol, 8-hydroxy-iso-hexahydrocannabinol, delta-9-tetrahydrocannabinol, Δ8-tetrahydrocannabinol, and cannabinol but also to the trifluoroacetic esters of Δ9-THC and Δ8-THC, when trifuoroacetic acid is used as protein precipitation agent. The amount of those newly revealed CBD transformation products depends on the GC injector temperature and on the extrahent type when extracts of the supernatants centrifuged from human plasma samples are analyzed after their preliminary protein precipitation by trifuoroacetic acid. Although trifuoroacetic acid as a protein precipitating agent has many disadvantages, it is quite often used for this purpose due to its very high protein precipitation efficiency. The results presented in the study demonstrate why the use of trifuoroacetic acid for plasma samples deproteinization should be avoided when CBD is determined by GC.