New arsenic species found in electronic cigarettes

Electronic cigarettes (e-cigarettes) are used by an increasing number of consumers since their introduction into the market in 2004, having reached about 16 % among high school students in 2015. Although different brands vary widely in design and appearance, they generally function in a similar manner: a solution known as e-liquid is vaporized by a battery-driven heating component and the generated aerosol is inhaled via a mouthpiece by the puffing consumer.

Photo: Different types of e-cigarettes including a disposable e-cigarette, a rechargeable e-cigarette, a medium-size tank device, large-size tank devices, an e-cigar, and an e-pipe.

E-liquids typically uses propylene glycol and/or glycerine as a solvent to dissolve flavoring chemicals, nicotine and other additives. Because these ingredients are simpler than the mixture chemicals generated by burning tobacco, e-cigarettes have been regarded as a less harmful alternative to tobacco smoking. However, numerous studies during the last years have found many health risks of e-cigarettes, including fine and ultrafine particles, volatile organic compounds (VOCs), endotoxins and toxic metals. Also several studies have found the presence of arsenic in the e-liquids or the generated aerosol.  Since the toxicity of arsenic depends very strongly on the species being present, the total concentration being reported is not a good enough information for evaluating the health risk.

The aim of the new study was to determine the concentration of the arsenic species being present in e-liquids and the aerosols generated from them. A representative selection of seventeen most consumed e-liquids were purchased from suppliers in China and Canada. Aerosol samples were generated by vaping e-liquid samples using the tank-type e-cigarette devices. The condensed aerosol was collected then for subsequent arsenic speciation analysis.

Arsenic speciation analysis was performed by using high-performance liquid chromatography interfaced to inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Arsenic species were separated by a strong anion-exchange column operated under gradient elution mode. For quality control, the certified reference material CRM No.18 Human Urine was analyzed in parallel with samples.

The collision cell of the ICP-MS was flushed with He to suppress potential polyatomic interferences caused by ArCl+. The amount of arsenic species being determined was about 89% +- 14 % of the total arsenic found by direct ICP-MS determination. Using this methodology, six arsenic species could be determined in the e-liquids, including arsenate, arsenite, monomethylarsonic acid and three new species not reported previously. The same six arsenic species could also be detected in the aerosol samples, however with different distribution. The concentration of arsenite in the aerosol was significantly higher than in the original e-liquid.  The results of an estimation indicated that e-cigarette smokers could inhale inorganic arsenic species at an inhalation concentration nearly half of the permissible exposure limit (10 µg/m3) set by OSHA for the workplace. The researchers concluded that the health risk of e-cigarette use with respect to lung cancer might be serious calling for further research and regulatory considerations.

The original publication:

Agilent Technologies Inc. - 1260 Infinity Binary HPLC System

Agilent Technologies Inc. - 7700x ICP-MS

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Brief summary: Chemical speciation analysis for nutrition and food science

October 15, 2019: Accurate determination of arsenic and its species by internal standardization for quantification by ICP-MS

last time modified: April 15, 2020