Mass Spectrometry & Spectroscopy
Chasing clouds, catching chemicals: Bisphenols in e-liquids analysed with SPE and LC-MS/MS
James Edwards, Porvair Sciences
Vaping refers to the use of an electronic device to inhale an aerosol created through heating a liquid, commonly known as an e-liquid. E-liquids typically consist of propylene glycol (PG), vegetable glycerine (VG), nicotine and various fl avouring compounds. The popularity of vaping has increased signifi cantly since 2013, growing from 1.3% of adults vaping to 10.0% in 2023. This is especially true among young adults with 23% of 18 year olds reporting long term vaping by 2023 [1]. As the prevalence of vaping continues to rise, there is an increasingly urgent need to fully understand the emerging health risks associated with it. Previous research has identifi ed some potential harmful health effects of vaping e-liquids including cardiovascular damage [2-5], respiratory issues [6-8], reproductive issues [9, 10] and neurological damage [11, 12].
An overlooked health risk associated with the e-liquids is contamination with bisphenols, believed to migrate into the liquid from their packaging. However, research into the presence of bisphenols in e-liquids remains limited. Notably, one study detected bisphenol A in every sample tested [13], showing the need for further work to investigate both bisphenol A as well as other bisphenols which may be present.
Bisphenols are compounds composed of two phenolic rings, connected via a carbon with differing chemical groups attached. Figure 1 shows examples of three common bisphenols. They are important in the manufacturing of plastics, where they provide the structural backbone and offer desirable properties which are diffi cult to achieve with alternative materials.
This work utilised a polymeric solid phase extraction (SPE) technique using the Microlute®
CP HLB 96 well plate to develop a sample preparation method, validate
extraction of bisphenols from e-liquid solutions, and analyse 16 different brands of e-liquids for six different bisphenols - A, AP, E, F, S and Z.
Materials and Methods
Stock and Standards A stock solution of all six bisphenols (A, AP, E, F, S and Z) was prepared by dissolving in methanol (MeOH) at 1 mg/mL. Working solutions were prepared by diluting this stock solution in water to obtain standards of 2.5, 50, 100, 250, 2,500 and 5,000 ng/mL.
Matrix solution
For validation of the SPE procedure and preparation of matrix match standards, a solution of 70% vegetable glycerine (VG) and 30% propylene glycol (PG) (v/v) was prepared.
Samples Figure 1: Chemical structures of three commonly used bisphenol compounds – bisphenol A, S and F.
Despite their usefulness within plastic production, bisphenols pose signifi cant health risks primarily due to their endocrine disrupting properties [14]. This means that they interfere with the body’s hormone systems, with research linking them to cancer (breast, prostate, ovarian, testicular and colorectal) [15], metabolism disruption [16] and harm to reproductive health [17].
The regulation of bisphenols varies signifi cantly worldwide, with the European Union (EU) implementing the strictest regulations globally. In 2022, the European Food Safety Authority (EFSA) suggested a tolerable intake of 0.2 ng/kg bodyweight/day for bisphenol A [19]. This was made substantially lower than the EFSA’s 2015 temporary tolerable intake of 4 ng/kg bodyweight/day, based on additional data demonstrating bisphenol A’s greater toxicity. Following this, on the 20th January 2025, the EU banned the use and trade of bisphenol A and other hazardous bisphenol derivatives in food contact materials [18].
While e-liquids are not classifi ed as food products and are therefore excluded from current EU bisphenol regulations, their storage in plastic bottles creates a potential source of contamination. Additionally, because exposure occurs through inhalation rather than ingestion, the health risks are less well understood and could differ signifi cantly. For these reasons, it is important to assess the concentration of bisphenols in e-liquids, evaluate potential risks, and develop reliable sample preparation methods to enable further study.
16 different brands of e-liquids with a composition of 70% VG 30% PG were purchased from an online UK retailer. The e-liquids were primarily packed in polyethylene terephthalate (PET) bottles, with one packaged in an low density polyethylene (LDPE) bottle and four in plastics of unknown composition. The fl avours included unfl avoured, mint, cherry, passionfruit, mixed berries, melon and apple pear, cream and energy drink.
SPE method A 10 mg 96 well plate (Microlute® CP 10 mg HLB) with a positive pressure manifold
(UltraPPM™ Lite) was used for processing samples. Prior to performing the SPE, samples and matrix match solutions were diluted 1:1 with ultrapure water to reduce viscosity and improve liquid fl ow through the SPE plate.
• Conditioning: 0.5 mL of methanol • Equilibration: 0.5 mL of ultrapure water • Loading: 1 mL diluted sample • Wash: 0.5 mL of 20% methanol in water
• Drying step: The sorbent was dried at 20 PSI for 2 minutes using the positive pressure manifold
• Elution: 2 x 0.5 mL of 5% ammonium hydroxide in methanol (dried at 20 PSI for 2 minutes after each elution with the positive pressure manifold)
• Reconstitution: The eluate was evaporated using a nitrogen blowdown evaporator (Ultravap®
Mistral) at 30°C and reconstituted with 0.1 mL of ultrapure water
INTERNATIONAL LABMATE - NOVEMBER 2025
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