GC-AED Studies of Nicotine Fate in a Burning Cigarette

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Abstract
An atomic emission detector (AED) for a gas chromatograph (GC) can be used to selectively detect compounds labeled with stable isotopes, such as D, 13C, and 15N. This capability can be used to determine precursor-fate relationships within complex matrixes, using stable isotopes rather than radiolabeled isotopes. Employing stable isotopes removes the safety consideration associated with radiolabeling studies. Two previous reports have employed GC-AED in fate studies for 13C-labeled precursors. The goal of this study was to evaluate the utility of GC-AED for precursor-fate determinations in tobacco science. In this work, GC-AED was used to determine the fate of nicotine-d4 in a burning cigarette. GC-MSD was then employed to identify the compounds that the AED indicated contained D. Spectral confirmation of the presence of D was performed on each chromatographic peak of interest with both AED and MSD to ensure that the identification of the products was correct. Nicotine and nicotine-d4 standards were used to evaluate the effect of coelution of unlabeled compounds with the labeled compounds on the AED response for D. It was shown that the AED response for D at λ = 308 nm decreases with increased concentration of unlabeled compound. Detection at λ = 656 nm, however, is unaffected by the presence of the unlabeled compound. Compound-independent calibration is also possible at this wavelength. GC-AED studies with nicotine-d4 core injected into cigarettes demonstrated that most of the nicotine (79%) is distilled, unchanged, into the mainstream (MS) and sidestream (SS) smoke. The degradation products that do occur include 3-substituted pyridines and nicotine-oxidation products. These are found only in the SS smoke.