Cigarette smoke chemistry: conversion of nitric oxide to nitrogen dioxide and reactions of nitrogen oxides with other smoke components as studied by Fourier transform infrared spectroscopy

Abstract

Nitric oxide is both a critical biological toxin and an important messenger molecule, signalling events as diverse as nerve transmission and smooth muscle relaxation. Fresh cigarette smoke contains from 300 to 500 ppm nitric oxide. While there have been reports of the rate of oxidation of nitric oxide to nitrogen dioxide in cigarette smoke, none have utilized a real-time method and provided detailed kinetic data and modelling. In this paper we present a Fourier transform infrared spectroscopy (FT-IR) method for the simultaneous determination of nitric oxide and nitrogen dioxide in gas phase cigarette smoke and in a number of gaseous mixtures that model smoke. The method uses multivariate least-squares regression analysis, which allows simultaneous quantitation of several components even in the presence of overlapping peaks, and fast data acquisition for kinetic analysis. Model systems containing mixtures of nitric oxide and isoprene, methanol, and/or acrolein and acetaldehyde in air were studied. The concentrations of nitric oxide, isoprene, etc., in the model systems were chosen to duplicate those in authentic cigarette smoke. In our best model (a mixture of nitric oxide, methanol, and isoprene in air) the disappearance of nitric oxide and the appearance of nitrogen dioxide follow time courses that closely duplicate those for cigarette smoke. Furthermore, the production of nitrogen dioxide follows a time course that agrees with our previously published rate of the development of organic free radicals in cigarette smoke. The present work, therefore, substantiates the steady-state mechanism we previously proposed for the production of free radicals in gas phase cigarette smoke.