Evidence That Metal Particles in Cannabis Vape Liquids Limit Measurement Reproducibility

Abstract

Cannabis vaping involves the vaporization of a cannabis vaping liquid or solid via a vaping accessory such as a vape pen constructed of various metals or other parts. An increasing number of reports advocate for expansion of the testing and regulation of metal contaminants in cannabis vape liquids beyond the metals typically tested such as arsenic, cadmium, mercury, and lead to reflect the possibility of consumers' exposure to other metal contaminants. Metal contaminants may originate not only from the cannabis itself but also from the vape devices in which the cannabis vape liquid is packaged. However, metal analyses of cannabis vape liquids sampled from cannabis vaping devices are challenged by poor precision and reproducibility. Herein, we present data on the metal content of 12 metals in 20 legal and 21 illegal cannabis vape liquids. The lead mass fraction in several illegal samples reached up to 50 μg g^-1. High levels of nickel (max 677 μg g^-1) and zinc (max 426 μg g^-1) were found in illegal samples, whereas the highest copper content (485 μg g^-1) was measured in legal samples. Significant differences in metal mass fractions were observed in the legal cannabis vape liquid taken from two identical devices, even though the liquid was from the same lot of the same cannabis product. Metal particles in the vape liquids were observed by scanning electron microscopy, and laser ablation inductively coupled plasma mass spectrometry confirmed the presence of copper-, zinc-, lead-, and manganese-bearing particles, metals that are in common alloys that may be used to make vape devices. Colocalized particles containing aluminum, silica, and sodium were also detected. These results suggest that metal particles could be a contributing factor to poor measurement precision and for the first time, to the best of our knowledge, provide evidence of metal particles in cannabis vape liquids contained in unused cannabis vape pens.

Figure 1

Elemental mass fractions of studied cannabis vape liquids from legally purchased vaping devices (sample IDs 1–20) and illegal vaping devices (sample IDs 21–41).

Figure 2

Comparison of the legal versus illegal cannabis vape liquids when the measured mass fractions exceeded established tolerance limits for metals in European Pharmacopoeia general Chapter 5.20 on elemental impurities.

Figure 3

Mass fractions of studied metals in three replicate subsamples of the same legal cannabis vape liquid obtained from two individual vape devices (yellow bar device #1 and brown bar device #2).

Figure 4

Metal particles in an illegal cannabis vape liquid detected from sample 41 by SEM (a) and elemental map of Cu by LA-ICP-MS with several hotspots depicting Cu-containing particles (b). SEM image also shows distortion on the central grid caused by charging of the polyimide membrane of the QX-102 capsule.