Strategies for Nonpolar Aerosol Collection and Heavy Metals Analysis of Inhaled Cannabis Products

Abstract

The rapid growth of inhalable cannabis concentrates raises questions about the safety of acute and chronic exposure to these aerosol mixtures. Due to the nonpolar nature of the aerosol mixture created from cannabis vapor cartridges, traditional aqueous-based capture methods used in e-cigarette or tobacco cigarette studies for analysis of metals are insufficient. Moreover, hydrophobic cannabis concentrates are not miscible with dilute aqueous acids and therefore not ideal for metal spiking unlike electronic nicotine delivery systems. This study describes a method of spiking nonaqueous matrices with aqueous metals standards to investigate aerosolization and recovery of the metals. It also compares various methods for nonpolar aerosol capture and subsequent analysis of 10 metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, and Sn) in two model cannabis matrices, flower and concentrate. Spiked cannabis concentrates were vaped in commercially available cartridges, and their aerosol mixtures were investigated for recovery of heavy metals via ICP-MS. Spiked flower samples were also combusted to compare collection rates of the 10 metals. Results show that not all metals that are present in the concentrate or flower can be fully recovered in the aerosol capture processes at standard voltage settings or combustion temperatures. These studies also demonstrate the importance of a nonpolar solvent as part of the aerosol collection to increase the recovery of some metals. The high concentration of some metals seen in the concentrate suggests that the devices themselves are potential routes of exposure. The ICP-MS analysis method was further validated by evaluating different parameters including linearity, matrix effect, limit of detection, limit of quantitation, and repeatability.

Metals in Cannabis Vaporizer Aerosols: Sources, Possible Mechanisms, and Exposure Profiles

“…Group 2 cartridges generally had higher concentrations overall, but it is unclear if that is due to the difference in cartridge components, or the battery voltage/temperature inconsistencies (group 2 hardware components were not screened, and various batteries were used while group 1 components are discussed above and the same battery was used as the model system). It has been shown in previous work that the tubing condensation collection method and the two-impinger method are similar in their ability to capture metals in cannabis aerosol, so it is unlikely that the difference is due to the capture methodology.…”

“…Aerosol was generated and collected using a smoke machine method detailed in previous work . To generate the aerosol, a cartridge was connected to either a Yocan Uni Pro Box Mod battery (group 1 cartridges) or the brand-specific battery necessary to power that cartridge was used (group 2 cartridges).…”

“…The tubing was then rinsed out with acetone and the rinsate collected for analysis. These two collection methods were shown to be comparable for metals recovery in previous work . A total of 50 puffs of aerosol were collected for each cartridge experiment for a total volume of 3750 mL of aerosol passed through the apparatus throughout the course of the trial.…”

“…A Shimadzu inductively coupled plasma mass spectrometer 2030 (Shimadzu Scientific Instruments, Inc., Columbia, MD) was used to quantify the concentrations of elements in each sample. All organic samples were prepared (microwave digested) and analyzed on ICP mass spectrometry (MS) according to methods detailed in previous work . The aqueous impinger samples were diluted to 2% final acid concentration and injected without digestion.…”

“…Therefore, standard tests might not detect other elements which are leaching into the concentrate and subsequently being emitted into aerosol form. A recent study established a method for the collection of the highly nonpolar cannabis aerosol and to investigate the recovery of metals spiked into a cannabis matrix by analyzing the aerosol for the presence of 10 metals . The present study is the subsequent analysis of commercially available cartridges alongside a model matrix to measure the levels of 10 metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, and Sn) in their aerosols.…”