Free-Base Nicotine Determination in Electronic Cigarette Liquids by ¹H NMR Spectroscopy

E-liquids usually contain significant nicotine, which will exist primarily in two forms, monoprotonated and free-base, the proportions of which are alterable through the effective pH of the medium. The fraction of nicotine in the free-base form is α_fb, with 0 ≤ α_fb ≤ 1. When dosed via aerosol, the two nicotine forms have different mechanisms and kinetics of delivery, as well as differing implications for harshness of the inhaled aerosol, so α_fb is relevant regarding abuse liability. Previous attempts to determine α_fb in electronic cigarette liquids and vapor have been flawed. We employed the exchange-averaged ¹H NMR chemical shifts of nicotine to determine α_fb in samples of e-liquids. This method is rapid and direct and can also be used with collected aerosol material. The e-liquids tested were found to have 0.03 ≤ α_fb ≤ 0.84. The α_fb values in collected aerosol liquid samples were highly correlated with those for the parent e-liquids. E-liquids designed to combine high total nicotine level (addictive delivery) with low α_fb (for ease of inhalation) are likely to be particularly problematic for public health

Benzene formation in electronic cigarettes - Fig 1

<p>Formation of benzene by four mechanisms: <b>a.</b> dehydration according to GL + PG– 5 H₂O, with cyclization (note: individually, propylene glycol alone and glycerol follow different stoichiometries); <b>b.</b> decarboxylation of benzoic acid; <b>c.</b> oxidation of benzaldehyde to benzoic acid, followed by decarboxylation (dashed arrow—-> indicates that the exact reaction stoichiometry is not provided); and <b>d.</b> disproportionation (Cannizzaro reaction) of benzaldehyde to form benzoic acid + benzyl alcohol.</p

Benzene and Total Particulate Matter (TPM) in E-Cigarette Aerosols Generated Using Two Devices and Different Lab-Prepared Fluids Based on Propylene Glycol (PG) and/or Glycerol (GL).

<p>When Together, PG and GL Combined in Equi-volume Amounts. ¹³C-Labelled Compounds Only Present As Indicated.</p

Benzene levels in e-cigarette aerosols generated with two different devices, different power levels, and 50:50 propylene glycol:glycerol with and without nicotine, benzoic acid, and/or benzaldehyde.

<p>Benzene levels in e-cigarette aerosols generated with two different devices, different power levels, and 50:50 propylene glycol:glycerol with and without nicotine, benzoic acid, and/or benzaldehyde.</p

Occurrence and Toxicity of Disinfection Byproducts in European Drinking Waters in Relation with the HIWATE Epidemiology Study

The HIWATE (<b>H</b>ealth <b>I</b>mpacts of long-term exposure to disinfection byproducts in drinking <b>WATE</b>r) project was a systematic analysis that combined the epidemiology on adverse pregnancy outcomes and other health effects with long-term exposure to low levels of drinking water disinfection byproducts (DBPs) in the European Union. The present study focused on the relationship of the occurrence and concentration of DBPs with in vitro mammalian cell toxicity. Eleven drinking water samples were collected from five European countries. Each sampling location corresponded with an epidemiological study for the HIWATE program. Over 90 DBPs were identified; the range in the number of DBPs and their levels reflected the diverse collection sites, different disinfection processes, and the different characteristics of the source waters. For each sampling site, chronic mammalian cell cytotoxicity correlated highly with the numbers of DBPs identified and the levels of DBP chemical classes. Although there was a clear difference in the genotoxic responses among the drinking waters, these data did not correlate as well with the chemical analyses. Thus, the agents responsible for the genomic DNA damage observed in the HIWATE samples may be due to unresolved associations of combinations of identified DBPs, unknown emerging DBPs that were not identified, or other toxic water contaminants. This study represents the first to integrate quantitative in vitro toxicological data with analytical chemistry and human epidemiologic outcomes for drinking water DBPs