Analyzing “Vaping” Using HPLC and HS-GC–MS

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Researchers from the Lawrence Berkeley National Laboratory (Berkeley Lab) have identified the source of toxic emissions within electronic cigarettes (e-cigarettes) using headspace gas chromatography in tandem with mass spectrometry (HS-GC–MS) and high pressure liquid chromatography (HPLC) (1).

The use of e-cigarettes also known as “vaping” has increased dramatically across the globe, with 2.6 million adults using e-cigarettes regularly in the UK (2), while in the US the number of regular users was approximately 9 million, according to the latest data from the Centers for Disease Control and Prevention (CDC) (3).

Viewed and marketed as a “healthier” alternative to traditional tobacco products, the relative novelty of the product has led to a lack of public knowledge on the potential dangers of e-cigarette use and scientific studies are only beginning to understand the longer-term effects of “vaping”.

“Advocates of e-cigarettes say emissions are much lower than from conventional cigarettes, so you’re better off using e-cigarettes,” said Hugo Destaillats, Berkeley Lab, California, USA, in a news release issued by the laboratory.

“I would say, that may be true for certain users - for example, long-time smokers that cannot quit - but the problem is, it doesn’t mean that they’re healthy. Regular cigarettes are super unhealthy. E-cigarettes are just unhealthy,”
according to Destaillats.

Previous studies have established that e-cigarettes emit toxic and potentially carcinogenic compounds but the mechanism of emission had remained unverified. Furthermore, how variables such as temperature, type, and age of the device affect emission levels remained unclear.

Researchers simulated vaping using three types of e-liquid in two different vaporizers representing the two extremes of the price market: one containing one heating coil and the other containing two heating coils. Samples were taken at numerous stages including the first inhale and last inhale, and at varying temperatures. Further comparisons were made with aged devices.

Results indicated that the thermal decomposition of propylene glycol and glycerine, two prominent solvents in e-liquids, leads to the emission of the chemicals acrolein and formaldehyde. Emission levels increased by a factor of 10 between initial inhales and those inhales taken once the device had reached a steady temperature (steady state).

The speed at which this steady state is reached was dependent on the device and battery voltage but in one example, acrolein, a severe eye and respiratory irritant, saw an increase from 0.46 micrograms per inhale for the first five inhales to 8.7 micrograms per inhale once the device had reached its steady state.

Comparatively, conventional cigarettes emit 400 to 650 micrograms of acrolein per cigarette; assuming 20 inhales on an e-cigarette is equivalent to one cigarette, then the total emission of acrolein for an e-cigarette is roughly 90 to 100 micrograms.

The effects of device ageing were also tested and identified an increase in chemical emissions with device age. “This effect is consistent with the build-up of polymerization byproducts on or near the coil, leading to accumulation of the sort of residues that are often referred to in the blogosphere as ‘coil gunk’ or ‘caramelization’. Heating these residues would provide a secondary source of volatile aldehydes,” said Destaillats.

One of the key findings of the study was the lower emissions from the double coil e-cigarette when compared to the single coil e-cigarette. Researchers suggested this was due to the lower coil temperatures, which reacts less to the “coil gunk” that builds up through use.

The immense variety of e-cigarettes and e-liquids has made studying e-cigarettes difficult, however, almost all contain a combination of propylene glycol and glycerin.

Destaillats added, “Both are used for making artificial smoke on stage. The ratio between the two determines things like the volume of vapour cloud that you produce. They are considered safe for food.”

However, there have been very few if any studies on the safety of heating and inhaling propylene glycol and glycerin. “People are not drinking the liquids - they’re vaping them,” said Mohamed Sleiman, Berkeley Laboratory, California, USA. “So what counts is the vapour.”

By vaporizing liquids consisting solely of the solvents, the researchers detected significant levels of 31 harmful chemical compounds, including two that had never been previously found in e-cigarette vapour - propylene oxide and glycidol, both of which are probable carcinogens. This verified that propylene glycol and glycerin were the source of these emissions within e-cigarettes.

“Understanding how these compounds are formed is very important,” according to Destaillats. “One reason is for regulatory purposes, and the second is, if you want to manufacture a less harmful e-cigarette, you have to understand what the main sources of these carcinogens are.”

The researchers are working on a follow-up study focusing on the health and environmental impacts of e-cigarettes. 

References

1. M.Sleiman et al., Environ. Sci. Technol. DOI: 10.1021/acs.est.6b01741

1. Action on Smoking and Health. Fact sheet. Use of electronic cigarettes (vaporisers) among adults in Great Britain. May 2015. [Accessed 05/08/16] http://www.ash.org.uk/files/documents/ASH_891.pdf

1. C.A. Schoenborn and R.M. Gindi, Electronic Cigarette Use Among Adults: United States, 2014. NCHS Data Brief No. 217 October 2015.