Characterizing e-cigarette Liquid Compounds: Top Questions Answered

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Characterizing e-cigarette Liquid Compounds: Top Questions Answered

Team TFS
Team TFS

Electronic cigarettes were introduced in 2007 as an alternative to conventional tobacco products, and their use has significantly increased worldwide. Yet despite their growing popularity, little is known about the potential impact of e-cigarettes on human health. This is especially important in relation to the presence of flavoring compounds, solvents, additives and other components intentionally or unintentionally added with unclear long-term effects.


Characterizing e-cigarette liquid compounds.jpgAs you seek to understand the opportunities and challenges of analyzing e-cigarette liquid compounds, here are answers to some frequently asked questions:


What are regulatory bodies doing to address the unknown risks of e-cigarettes?


In 2012, the U.S. Food and Drug Administration (FDA) established a list of 93 “harmful and potentially harmful constituents” (HPHCs) in cigarette smoke, cigarette filler, and smokeless tobacco products.


Under section 904(a)(3) draft guidance of the Federal Food, Drug and Cosmetic Act (the FD&C Act), only a representative subset of 20 HPHCs to be reported by tobacco product manufacturers for combustible products are detailed.


Additionally, under section 910 draft guidance of the FD&C Act, 29 HPHCs have been outlined in the Premarket Tobacco Products Applications (PMTA) guidance for Electronic Nicotine Delivery Systems (ENDS).


In May 2016 the Tobacco Products Directive (TPD) 2014/14/EU5 introduced new rules for nicotine-containing electronic cigarettes and refill containers (Article 20), to protect human health and meet the obligations of the European Union under the World Health Organization’s WHO Framework Convention on Tobacco Control. In the UK, the majority of the provisions under article 20 are implemented by the Medicines and Healthcare products Regulatory Agency (MHRA). Other EU member states have transposed the EU TPD into their own national laws and assigned competent bodies to oversee.



What analytical technologies are used for the qualitative and quantitative assessment of electronic cigarette liquids (e-liquids)?


The most frequently used technologies to analyze e-liquids are liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS), but both techniques can have limitations with regard to mass accuracy, sensitivity and linear dynamic range. GC-MS triple quadrupole and GC-FID would typically only be used for quantification of known compounds in e-liquids. An alternative approach is high-resolution accurate mass (HRAM) mass spectrometry which can achieve confident targeted and non-targeted compound identification and quantitation.


Are there any challenges associated with using these technologies?


There are several analytical challenges associated with the analysis of e-cigarette liquids using GC or GC-MS. To have good coverage of the chemical content, you need to use a GC-MS platform that can sensitively and selectively detect chemical constituents, taking into account the variety and complexity of possible matrices.


GC coupled to high-resolution mass spectrometry is one of the most appropriate, as it offers both the required sensitivity and selectivity. In particular, GC-Orbitrap MS with sub-ppm mass accuracy, versatility for sample introduction, and combined with unique software algorithms for automated deconvolution and extensive spectral libraries, make it a powerful solution for both qualitative and quantitative assessments of e-liquids, all while operating in full scan acquisition mode.


What if I can’t (or don’t want to) use liquid injections?


Although liquid injections are commonly used in GC-MS workflows for this analysis, an alternative is solid phase micro extraction (SPME), which is a solvent-free technique that combines sample extraction with concentration in a single step. It consists of a fused-silica fiber coated with an organic phase that acts by extracting and concentrating the analytes present using selective adsorptive/absorptive processes. The fiber can be exposed to the headspace or via direct immersion in the sample.


Where can I learn more about chemical characterization of e-cigarette liquids?

In a recent study, Thermo Fisher Scientific used specific analytical systems to perform qualitative analysis of e-liquids on a targeted subset of the US FDA list of HPHCs. The study also used an untargeted approach to screen the samples for other potential toxic chemicals that may be present. The study demonstrated that using specific GC-MS technology, with unique intuitive software workflows for automated deconvolution and extensive spectral libraries, it’s possible to achieve excellent analytical results for e-liquids.


Read more about the study and workflow.

Read the Knowledgebase post: How to characterize chemicals in e-cigarette liquids with Orbitrap GC-MS


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