ICP-MS Determination of 23 Elements of Potential Health Concern in Liquids of e-Cigarettes. Method Development, Validation, and Application to 37 Real Samples

Abstract

The lack of interest in the determination of toxic elements in liquids for electronic cigarettes (e-liquids) has so far been reflected in the scarce number of accurate and validated analytical methods devoted to this aim. Since the strong matrix effects observed for e-liquids constitute an exciting analytical challenge, the main goal of this study was to develop and validate an ICP-MS method aimed to quantify 23 elements in 37 e-liquids of different flavors. Great attention has been paid to the critical phases of sample pre-treatment, as well as to the optimization of the ICP-MS conditions for each element and of the quantification. All samples exhibited a very low amount of the elements under investigation. Indeed, the sum of their average concentration was of ca. 0.6 mg kg−1. Toxic elements were always below a few tens of a μg per kg−1 and, very often, their amount was below the relevant quantification limits. Tobacco and tonic flavors showed the highest and the lowest concentration of elements, respectively. The most abundant elements came frequently from propylene glycol and vegetal glycerin, as confirmed by PCA. A proper choice of these substances could further decrease the elemental concentration in e-liquids, which are probably barely involved as potential sources of toxic elements inhaled by vapers.

Toxicological Assessment of Particulate and Metal Hazards Associated with Vaping Frequency and Device Age

“…We observed increasing concentrations of manganese and arsenic, but these were not statistically significant. Common metal species such as copper, iron, nickel, and zinc were found to be within ranges of other cartridge-type devices previously reported, most likely leached from the metal heating element as previously described within the plastic pod, and notably, arsenic, barium, and lead concentrations were higher than previously found within the literature [ 37 , 49 ]. This is concerning given that these elements also indicated higher concentrations in the corresponding puff fractions within the context of human exposure.…”

“…A performance check specified by the manufacturer recommendation was performed using a tuning solution to monitor the optimal instrumental conditions. For e-liquid sample analysis, the mass of the e-liquid (tobacco flavor, 5% nicotine, commercially available) analyzed by ICP-MS was approximately 300 mg and was prepared with a dilution of 2% nitric acid solution (ARISTAR ® PLUS for trace metal analysis, VWR Chemicals BDH ® , Radnor, PA, USA) up to 50 mL as described in the previous metal analysis study by Mara and colleagues [ 37 ]. The aerosol samples were prepared by fully evaporating 10 mL of the 75% methanol solution using a centrifuge concentrator (Vacufuge Plus, Eppendorf, Hamburg, DEU) set at 60 °C for about 2 h. The dilute 2% nitric acid solution described previously was then added to the dried samples.…”

Transfer of Metals to the Aerosol Generated by an Electronic Cigarette: Influence of Number of Puffs and Power

“…Metal concentrations in the tank and aerosol samples were measured using a graphite furnace atomic absorption (GFAA) AAnalyst 600 spectrometer (Perkin Elmer, Waltham, MA, USA). Although ICP-MS is commonly used for metal analysis of e-liquids and aerosol [ 25 , 51 , 54 ], GFAA was chosen in this study for the ability to measure very small volumes of sample, and accessibility to the instrument, although fewer elements were able to be quantified compared to ICP-MS. Chromium, nickel, copper, and lead concentrations were measured by diluting the e-liquid samples by a factor of 2 with 1% ultrapure nitric acid (chromium, copper, and lead) and a factor of 10 for nickel. No further digestion of the samples were performed and dilutions were performed in 1% nitric acid [ 55 , 56 ].…”

The Effects of E-Cigarette Aerosol on Oral Cavity Cells and Tissues: A Narrative Review

“…Other research has supported these results, with an emphasis on their potentially harmful effects for human health [27,28]. Nevertheless, multiple potentially harmful components, toxic metals and trace elements, e.g., aluminium, lead, mercury, zinc, carbonyls, epoxides, policyclic aromatic hydroxycarbons (PAHs) and pesticides were found in e-liquids and aerosols [29][30][31][32][33]. New methods used to estimate toxic metal-containing particles in e-aerosols of various pod-type systems are permitted to detect metal-containing particles such as chromium, zinc, iron, cooper, tin, and lead in various concentrations [34].…”