THC Can Chemically Bond With Vitamin E Acetate in Vape Liquids, Study Finds
Tetrahydrocannabinol (THC) and vitamin E acetate (VEA) compounds can become linked with hydrogen bonds, according to a new paper published in the journal Analytical Chemistry.
The study, authored by members of the US Food and Drug Administration’s (FDA’s) Forensic Chemistry Center, details the results of a recent investigation that discovered the presence of a hydrogen bonded THC/VEA complex in un-vaped e-liquids, vaped e-liquids, and the aerosol produced from vaporizing e-liquids.
The discovery comes at the tail end of the US’s recent vaping crisis, which both THC and VEA were heavily implicated in.
What is VEA?
Vitamin E acetate, a diluent thickener known to be used in illicit market THC vape products, has been officially identified by the US Centers for Disease Control and Prevention (CDC) as the cause behind the outbreak of vaping-related lung injuries being seen in North America.
“Vitamin E acetate is strongly linked to the EVALI [e-cigarette or vape produce use-associated lung injury] outbreak,” stated the CDC’s official fact sheet on the outbreak. “Vitamin E acetate has been found in product samples tested by FDA and state laboratories and in-patient lung fluid samples tested by CDC from geographically diverse states.”
“However, evidence is not sufficient to rule out the contribution of other chemicals of concern, including chemicals in either THC or non-THC products, in some of the reported EVALI cases.”
As of January 21, 2020, the CDC reports that there have been a total of 2,711 hospitalized EVALI cases, including 60 deaths. Emergency department visits related to EVALI appear to have peaked in September 2019, with numbers slowly declining since then. However, vaping-related hospitalizations have yet to fall back to baseline levels.
Latest figures show that 82 percent of patients admitted to hospital with EVALI reported using THC-containing products. While this high incidence may simply be down to the majority of EVALI patients acquiring their THC products from informal or illicit sources which are more likely to contain VEA, a lack of evidence ruling out other contributing factors has motivated further study of VEA and THC-containing vape products.
Discovering the THC/VEA complex
Using Fourier-transform infrared spectrometry (FTIR), nuclear magnetic resonance (NMR) spectrometry, and direct analysis in real time ionization coupled to a high-resolution mass spectrometer (DART-HRMS), the FDA scientists in the Analytical Chemistry study analyzed various different vape samples from hospitals, state laboratories, and related FDA investigations.
The suspect vape samples were compared against a 50:50 un-vaped THC/VEA control mixture prepared in the laboratory, a pure THC control, and a VEA control, in each of these spectroscopy apparatus. 
in suspect e-liquids, the hydrogen bond highlighted in red.
The FDA scientists observed significant differences between the FTIR absorption spectra of the suspect e-liquids and in-house THC/VEA mixture compared to the individual THC and VEA controls. Differences in the e-liquid absorption spectra fell inside the wavenumber ranges corresponding to changes in C=O bonding, C-O bonding, and OH bonding.
From this FTIR absorption spectra data, taken in combination with information gleaned from scientific literature, the FDA scientists hypothesized that a hydrogen bonded THC/VEA complex is being formed inside VEA-containing e-liquids.
Further examination using carbon-13 NMR revealed a downfield shift in the carbonyl peak region, consistent with the presence of hydrogen bonding. The proposed structure and existence of the hydrogen bond was also supported by the results generated using DART-HRMS.
What does the discovery mean?
In the paper, the FDA scientists reveal that the results of this study have already led to additional research into the adverse health effects associated with vaping VEA.
“While analysis of the effects of vaporizing VEA is beneficial, understanding the interactions between VEA and other constituents commonly found in the vape cartridges in various phases could provide additional information needed to better understand the cause of EVALI,” the authors wrote.
“While this work doesn’t directly link the hydrogen bonded complex to EVALI, it demonstrates that the complex is present in the aerosol produced under the vaping conditions used here and would likely be delivered to the lungs in this form.”
Given that this would put the THC/VEA complex at the primary site of lung injury, the researchers advise that further work should look into how this complex may impact the formation of toxic pyrolysis byproducts and, consequently, harm the lungs.
