Sample preparation methods for elemental analysis in electronic cigarette aerosols: a critical review

In the last decade, e-cigarettes have been marketed as a less harmful alternative to classical tobacco smoking and are currently being used by millions of people. An e-cigarette consists of an e-liquid and a heating device, generating an aerosol that the user can inhale. Recently, several studies have shown that metals and metalloids, including As, Cd, and Pb, known carcinogens, were present in these aerosols. To ensure the accuracy of dose-toxicity estimations, it is essential to have access to reliable and reproducible methods for estimating the dose in question. Although more standardization methodologies were introduced in the analysis of metal(loid)s from aerosols, a huge divergence in sample preparation can be found in the literature. This work aimed to provide an overview of the sample preparation methods used to quantify these metal(loid)s. Therefore, a literature search was conducted in September 2024, that followed the PRISMA guidelines. Among the 48 articles selected, a wide variability in sample preparation was observed, specifically variations in aerosol generation characteristics and collection techniques. Despite the widespread use of methods as filters and impingers, many studies failed to validate critical steps such as aerosol recovery, blank corrections, and the extent of matrix effects. In addition, poor inorganic methodological practices were often applied, such as excessive use of glass materials for aerosol collection or other sample preparation steps. Therefore, further standardization of methodologies is urgently needed to improve the reliability of metal quantification in e-cigarette aerosols, which could potentially enhance regulatory frameworks and facilitate the routine analysis of e-cigarette emissions.