A light at the end of the tunnel – E-cigarette analysis made easy with TD and TOF MS
Wednesday, 15 October 2014 at 9:51:AM
Smoking has never been far from the headlines over recent months, with the forthcoming ban on smoking in cars carrying children in England and Wales having gained a considerable amount of media attention, and the rise in awareness in indirect impacts of smoking such as third-hand smoke.
A particular focus of attention has been the e-cigarette phenomenon and the potential for harm from these mimics of real cigarettes. As a consequence, the UK Government has proposed a ban on e-cigarette sales to under-18s in England, and there are also moves afoot in the USA, with e-cigarettes proposed to come under the remit of the US FDA.
E-cigarette liquids vary widely in composition, but typically contain a variety of flavourings, with or without nicotine, dissolved in a carrier liquid such as glycerol or propylene glycol (1,2-propanediol). Heating this liquid within the e-cigarette generates a vapour, which following inhalation into the lungs, generates a visible ‘fume’ upon exhalation.
However, a meta-review of e-cigarette constituents, published earlier this year, found that commerical e-cigarette solutions can contain a number of potentially harmful chemicals, including formaldehyde, nitrosamines, and polycyclic aromatic hydrocarbons (PAHs). The presence of such chemicals naturally gives rise to some concern, and has already led analytical scientists to examine e-cigarette vapour itself in more detail.
One such study was carried out last year by Tobias Schripp and co-workers at the Fraunhofer Wilhelm-Klauditz-Institut (WKI) in Braunschweig, Germany. They used chamber sampling with Markes’ UNITY-ULTRA and GC–quadrupole MS to identify the mix of chemicals that is released upon ‘vaping’, and how this changes after exhalation.
However, a presentation by Stuart Martin and Chris Rawlinson (of tobacco company British American Tobacco - BAT) at a scientific conference on Smoke Science & Product Technology in September 2013 makes a compelling case that quadrupole MS detectors are not sufficiently sensitive to adequately characterise vapour from e-cigarettes. This is because although e-cigarettes emit a lot less particulate matter than regular tobacco (since no combustion takes place), they still produce a wide range of compounds at trace levels.
Having previously been in conversation with our specialists on how to analyse cigarette smoke, Martin and Rawlinson turned to our TD–GC–TOF MS system to tackle the problem of e-cigarettes. They weren’t disappointed. The concentrating power of TD and sensitivity of the BenchTOF not only allowed them to identify about 130 components (twice as many as before), but greatly shortened the sampling too, because they were able to replace the cumbersome smoking machine with a much simpler syringe drive. This collected just 25 mL of e-cigarette vapour on to a TD tube packed with Tenax TA and SulfiCarb, which was then conveniently desorbed on a Markes TD-100 before transfer to the GC–MS.
Remarkably, the total time for analysis and data-processing was less than 30 minutes – a speed that they say could allow 100 samples to be processed every day, a vast improvement on the eight samples per day obtainable with existing technology. At the same time, they were able to reduce limits of detection from 0.1 µg to less than 5 ng on-tube – a 20-fold increase in sensitivity.
The presentation concludes that, although existing analytical ‘smoking machines’ in conjunction with GC–quadrupole MS may be suitable for assessing the bulk components of e-cigarettes, they are not suitable for in-depth screening, and present the combination of Markes’ TD and TOF MS technologies as a powerful alternative.
David Barden received his Ph.D. in Organic Chemistry from Cambridge University in 2004, and during his time as an editor at the RSC wrote news pieces for Chemistry World on various scientific topics. He is now Technical Copywriter at Markes International, where he draws on the expertise of his colleagues to explain how new thermal desorption and mass spectrometry technologies can be applied to analyse volatile organic compounds in a wide variety of situations.