HS-GC–MS and HPLC–DAD Uncover High Levels of Harmful Compounds in Disposable Electronic Cigarettes

A study by researchers at the University of Huddersfield provided detailed chemical characterization of 60 disposable electronic cigarettes (ECs), revealing significant concerns over the presence and concentration of ethyl maltol and benzoic acid (1). Using headspace gas chromatography–mass spectrometry (HS-GC–MS) and high performance liquid chromatography with diode array detection (HPLC–DAD), the researchers assessed both new and used ECs to evaluate chemical content and behavior across usage.

Available in a wide range of flavours, disposable vapes are popular among younger consumers, potentially because of the belief that vaping is less harmful than smoking (2). Their rapid uptake has outpaced toxicological research, especially regarding the compounds inhaled during use. The research team sought to address this gap by quantifying harmful chemicals in a broad sample of single-use ECs. Their research was published in the Journal of Chromatography A.

For volatile and semi-volatile analytes, HS-GC–MS was employed. For the quantification of analytes in aqueous matrices—particularly those simulating deposition in lung tissue—the team utilized HPLC–DAD. Method validation confirmed limits of detection (LODs) for benzoic acid and ethyl maltol at 0.0018 mg/mL and 0.00033 mg/mL, respectively. The limit of quantitation (LOQ) was calculated as three times the LOD, with an LOQ of 0.0053 mg/mL for benzoic acid and 0.0011 mg/mL for ethyl maltol.

Across 55 analyzed EC liquids, ethyl maltol was detected in 89% of samples, while benzoic acid appeared in 87%. Notably, 42% of products contained ethyl maltol concentrations more than ten times higher than the General Standard for Food Additives (GSFA) threshold for comparable oral exposures. Meanwhile, 71% of benzoic acid-containing samples exceeded 20 times the concentrations previously associated with genotoxicity in human lymphocytes.

Ethyl maltol, known for imparting a sweet, candy-like aroma, showed concentrations between 2–14 mg/mL, with the highest levels found in fruit- and dessert-flavoured products. Benzoic acid concentrations ranged from 2–31 mg/mL, closely tracking nicotine content.

The team used a custom-built dual impinger setup to simulate vaping and evaluate chemical release dynamics. Aliquots were collected after every 20 puffs and analyzed by HS-GC–MS. From puff 0–40, both ethyl maltol and benzoic acid levels decreased due to e-liquid depletion. Between puffs 40–80, concentrations rose significantly—by up to 74% for ethyl maltol and 35% for benzoic acid—likely because of increased thermal decomposition and evaporative loss of more volatile components.

By analyzing both new and user-donated ECs, the researchers confirmed significant chemical variability between devices. In 77% of cases, used ECs exhibited higher benzoic acid concentrations. Ethyl maltol was elevated in 60% of used devices. However, batch-to-batch variations suggested manufacturers may be reformulating e-liquids to meet changing regulations or sensory preferences, complicating interpretation.

The findings of this study also carry regulatory implications. With flavouring agents like ethyl maltol often evaluated only for oral exposure, their inhalation toxicity remains poorly characterized (1). The limited data available suggest that these chemicals exhibit cytotoxic and genotoxic effects at concentrations found in the analyzed samples. For example, benzoic acid is not only genotoxic at high concentrations but may also convert to benzene—a known human carcinogen—under vaping conditions.

The team concluded by stating that their findings consolidate concerns over the safety of ECs. The study also highlights the rapid evolution of EC formulations—often outpacing toxicological data and regulatory oversight.

References

(1) Pennington, C.; Hernandez Aldave, S. Disposable Electronic Cigarettes: Chemical Composition in New and Used Devices. J. Chrom. A 2025, 1758, 466178. DOI: 10.1016/j.chroma.2025.466178

(2) John Hopkins Medicine. 5 Vaping Facts You Need to Know. https://www.hopkinsmedicine.org/health/wellness-and-prevention/5-truths-you-need-to-know-about-vaping#:~:text=According%20to%20Blaha%2C%20there%20are,tobacco%20products%20down%20the%20road(accessed 2025-08-15).