Abstract
The submicron liquid droplets constituting the particulate matter of mainstream tobacco smoke (PM~MTS~) are viscous and of a composition that is complex and poorly understood. PM~MTS~ is often ∼80% w/w ‘tar’ where ‘tar’ = total PM~MTS~− (nicotine + water). Many of the chemical agents in MTS responsible for smoking‐related cancers are found at least partially in the PM~MTS~ portion of MTS. The properties of PM~MTS~ vary with brand and with puffing patterns. The chemical forms and total levels of nicotine, the identities/levels of other compositionally dominant compounds, and the identities/levels of carcinogens are of interest. Most studies of the composition of PM~MTS~ have involved extraction then chromatography. Such methods allow the determination of low‐level constituents, but alter the samples such that direct information regarding chemical conditions within the PM~MTS~ cannot be obtained. Here, we utilize nuclear magnetic resonance spectroscopy (NMR) to examine native PM~MTS~ in conventional cigarettes, including measurements of the brand‐dependent fraction of PM~MTS~ nicotine that is in the free‐base form (increasing this fraction in inhaled tobacco smoke affects the rates of the processes governing nicotine deposition in the respiratory tract, and so has implications for smoking behavior and addiction). We also demonstrate the use of NMR for characterizing the composition of PM~MTS~ (including the levels of selected cigarette additives) when the cosolvent DMSO‐d~6~ is added to improve spectral resolution. The native and solvent‐assisted results open the door to a range of future studies. Copyright © 2006 John Wiley & Sons, Ltd.