This report describes a new method for estimating the retention of selected mainstream smoke constituents in the respiratory tract of adult smokers during cigarette smoking. Both particulate-phase (PP) constituents including nicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and N'-nitrosonornicotine (NNN), two tobacco-specific nitrosamines (TSNA), and gas-vapor-phase (GVP) constituents including carbon monoxide (CO), isoprene (IP), acetaldehyde (AA), and ethylene, were studied. To estimate the amounts of smoke constituents delivered during smoking, we used predetermined linear relationships between the measured cigarette filter solanesol content and machine-generated mainstream deliveries of these selected compounds. To determine the amounts of smoke constituents exhaled, the expired breath was directed through a Cambridge filter pad (CFP) attached to an infrared spectrometer. PP compounds were trapped on the CFP for later analysis and GVP compounds were analyzed in near real time. The smokers' respiratory parameters during smoking, such as inhalation/exhalation volume and time, were monitored using LifeShirt(R), a respiratory inductive plethysmography (RIP) device. The retention of each smoke constituent, expressed as a percentage, was then calculated as the difference between the amount delivered (estimated) and the amount exhaled relative to the amount delivered. We studied 16 adult male smokers who smoked cigarettes according to 3 predefined smoking patterns: no inhalation (pattern A), normal inhalation (pattern B), and deep inhalation (pattern C). For the three PP constituents, the mean retentions for pattern A ranged between 10 and 20%; and while the mean retentions of the two TSNAs were significantly higher for pattern C (84% for NNK and 97% for NNN) than those for pattern B (63% for NNK and 84% for NNN), the mean retentions of nicotine were basically the same between patterns B and C, which were both greater than 98%. For the GVP constituents, the retentions were similar between pattern B and pattern C, although different constituents were retained to different degrees (average values of 33%, 52%, 79%, and 99% for ethylene, IP, CO, and AA, respectively). The differences in the retention between different constituents could be interpreted in terms of each constituent's physical properties such as volatility and solubility. In conclusion, the method described is suitable for studying the retention of selected mainstream smoke constituents in the respiratory tract of smokers.

The development, during the last decade, of modern step-scan interferometry instrumentation has allowed FT-IR to be applied to the study of time-dependent phenomena in ways not previously possible, because of the problems of uncoupling the spectral multiplexing from the temporal domain in the continuous-scan FT-IR mode. Specifically, the time regime from tens of nanoseconds to tens of milliseconds has been accessible to time-domain measurements to only a very limited degree with continuous-scan instrumentation and not at all for modulation-demodulation (frequency-domain) experiments in this time range. The step-scan technique not only works very well in this time regime and for slower phenomena, but is only prevented from application to faster processes by the signal strength, the speed of available detectors, the intensity of sources, and the speed and sophistication of the electronics. This paper surveys the various types of experiments which are either enhanced by use of step-scan FT-IR methods or are only possible by use of these techniques. The principles of step-scan instrumentation are reviewed, particularly those of retardation control, signal generation, and data acquisition, as well as the place of step-scan FT-IR relative to other techniques of dynamic vibrational spectroscopy. The importance of path difference (phase) modulation, particularly in frequency-domain measurements, the extraction and use of the signal phase, the creation of 2D FT-IR spectra, and the strategies for acquisition of both time- and frequency-domain data in the step-scan mode are discussed and illustrated.

There is significant regulatory and economic need to distinguish analytically between tobacco-derived nicotine (TDN) and synthetic nicotine (SyN) in commercial products. Currently, commercial e-liquid and oral pouch products are available that contain tobacco-free nicotine, which could be either extracted from tobacco or synthesized. While tobacco products that contain TDN are regulated by FDA Center for Tobacco Products, those with SyN are currently not in the domain of any regulatory authority. This regulatory difference provides an economic incentive to use or claim the use of SyN to remain on the market without submitting a Premarket Tobacco Product Application. TDN is ~99.3% (S)-nicotine, whereas SyN can vary from racemic (50/50 (R)/(S)) to ≥ 99% (S)-nicotine, i.e., chemically identical to the tobacco-derived compound. Here we report efforts to distinguish between TDN and SyN in various samples by characterizing impurities, (R)/(S)-nicotine enantiomer ratio, (R)/(S)-nornicotine enantiomer ratio, and carbon-14 (14C) content. Only 14C analysis accurately and precisely differentiated TDN (100% 14C) from SyN (35–38% 14C) in all samples tested. 14C quantitation of nicotine samples by accelerator mass spectrometry is a reliable determinate of nicotine source and can be used to identify misbranded product labelled as containing SyN. This is the first report to distinguish natural, bio-based nicotine from synthetic, petroleum-based nicotine across a range of pure nicotine samples and commercial e-liquid products.

We have fabricated miniature planar IR waveguides with thicknesses of 30-50 mum, consisting of 12-mm long, 2-mm wide strips of Ge supported on ZnS substrates. Evidence for efficient propagation of broadband IR light through these waveguides is provided by the presence of characteristic high- and low-frequency optical cutoffs of Ge; by the observation of an oscillatory interference pattern in the transmittance spectrum, which exhibits a dependence on waveguide thickness and propagation angle that closely matches waveguide theory; and by the detection of strong evanescent-wave absorption from small (2 mm(2)) droplets of liquid, e.g., water, on the waveguide surface. As also predicted by theory, the surface sensitivity (detected light absorbance per unit area of sample-waveguide contact) is shown to increase as a function of incidence or bevel angle.

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