1. Liquid Chromatographic Analysis of Carbonyl Compounds in Aerosols from High and Low Nicotine E-Cigarette Liquids Mirroring Realistic Puffing Topography
Kimber CF1, Kośmider L2, Kurek J2, Corcoran O3, Dawkins LE4
1) Drugs and Addictive Behaviours Research Group, School of Psychology, University of East London, Water lane, Stratford, London, E15 4LZ, UK ; 2) Institute of Occupational Medicine and Environmental Health, Poland; 3) The Medicines Research Group, School of Health, Sport and Bioscience, University of East London, Stratford campus; 4) Division of Psychology, School of Applied Sciences, 103 Borough Road, London South Bank University, London, SE1 0AA, UK
Introduction
Results
Tobacco smokers engage in more intensive puffing regimes (more frequent and longer puffs) when switching from higher to lower nicotine-containing cigarettes [1,2,3,4], this can result in increased toxicant exposure [5]. Such compensatory puffing behaviour has recently been demonstrated in experienced vapers using high and low nicotine concentration liquids in the lab [6]. Although exposure to toxins in e-cigarette aerosols is negligible by comparison with tobacco smoke [7], whether a more intensive puffing regime associated with using a lower nicotine concentration liquid increases exposure, has not been explored. This research is particularly timely with the recent introduction (20th May 2016) of the European Tobacco Product Directive (EU-TPD).
In the liquid, there was no statistical difference between conditions for levels of acetaldehyde (p = 0.41). Levels of formaldehyde, acetone and acrolein were either not detected (N.D) or below the limit of quantification (BLQ).
In the aerosols, based on participants’ puffing topography, levels detected were as follows for: formaldehyde 3.41 ±0.94 vs 1.49 ±0.30, acetaldehyde ±0.36 vs 1.04 ±0.13 and acetone 0.73 ±0.20 vs 0.28 ±0.14 (all p < 0.01) in the 6 and 24 mg/mL nicotine concentration liquids respectively. Acrolein was not detected (figure 3).
Table 2. Levels of carbonyl compounds found in liquids
Levels (µg/50µl) in Liquids
Formaldehyde
Acetaldehyde
Acetone
Acrolein
6 mg/mL
N.D
0.059 – 0.075
BLQ
24 mg/mL
0.043 – 0.067
0.080 – 0.094
Aims
To establish whether more intensive puffing regimes associated with using a lower nicotine concentration produces higher levels of toxicants from e-cigarette nicotine aerosols.
Table 3. Levels of carbonyl compounds found in aerosols
Levels (µg) in Aerosols
Formaldehyde
Acetaldehyde
Acetone
Acrolein
6 mg/mL
N.D
24 mg/mL
Methodology
HPLC/diode array analysis was employed. Four carbonyl compounds formaldehyde, acetaldehyde, acrolein and acetone were quantified in liquid (vehicle of propylene glycol and vegetable glycerine 50/50%) and aerosol using 24 mg/mL and 6 mg/mL nicotine concentration liquids. Aerosols were generated by a smoking machine (figure 2; University of Technology, Lodz, Poland [8]) configured to exactly replicate puffing topography data obtained from a sample of 12 experienced vapers using both aforementioned solutions, for 1 h [6].
The ‘Joyetech eVic Supreme’ e-cigarette (figure 1) (output voltage 3.9) was mounted with the Aspire Nautilus BVC tank (atomiser 1.8 Ohm). The 6 mg/mL liquid was used more intensively compared to the 24 mg/mL. Results are presented in number of puffs taken on average for 1 h of e-cigarette use (74 and 47 for 6 and 24 mg/mL liquids respectively as per the puffing topography in Dawkins et al, in press; table 1). Analyses was performed 6 times for each solution. T-tests were used for comparing the means in aerosols and in solutions.
Figure 2. Smoking machine
Figure 3. Levels of toxicants detected in aerosols
Table 1. Puffing protocol used in the study
* P < 0.01; whiskers - SEM
Puff duration
Number of puffs
Intervals between puffs
Sampling time
24 mg/mL
3.76s. 14
74.5s.
1017s.
6 mg/mL
5.04s.
44.3s.
641s.
Conclusions
The smoking machine, programmed with a more intensive puffing regimen to reflect compensation by experienced vapers on lower nicotine concentration liquid, resulted in higher aerosol levels of formaldehyde, acetaldehyde and acetone. Our findings suggest, vapers making a sudden switch to much lower nicotine concentration liquid (either due to the EU-TPD implementation or personal choice) may inadvertently increase their exposure to carbonyl compounds through compensatory puffing behaviour.
Figure 1. E-cigarette and tank used in the study
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Competing interests
No financial support from any companies was received for this work and there are no non-financial conflicts of interest that would be considered relevant to this work. CFK, LK and JK declare no competing interests.
LED and OC have previously conducted research for several independent electronic cigarette companies. These companies had no input into the design, conduct or write up of the projects. LED has also acted as a consultant for the pharmaceutical industry and as an expert witness in a patent infringement case.