title: Kinetic modeling of nicotine in mainstream cigarette smoking.
abstract: BACKGROUND
  The attempt to understand the kinetic behavior of nicotine in tobacco will provide a basis for unraveling its energetics in tobacco burning and the formation of free radicals considered harmful to the cigarette smoking community. To the best of our knowledge, the high temperature destruction kinetic characteristics of nicotine have not been investigated before; hence this study is necessary especially at a time addiction science and tobacco research in general is gaining intense attention.
  
  
  METHODS
  The pyrolysis of tobacco under conditions simulating cigarette smoking in the temperature region 200-700 °C has been investigated for the evolution of nicotine and pyridine from two commercial cigarettes coded ES1 and SM1 using gas chromatography hyphenated to a mass selective detector (MSD). Moreover, a kinetic model on the thermal destruction of nicotine within a temperature window of 673 and 973 K is proposed using pseudo-first order reaction kinetics. A reaction time of 2.0 s was employed in line with the average puff time in cigarette smoking. Nonetheless, various reaction times were considered for the formation kinetics of nicotine.
  
  
  RESULTS
  GC-MS results showed the amount of nicotine evolved decreased with increase in the puff time. This observation was remarkably consistent with UV-Vis data reported in this investigation. Generally, the temperature dependent rate constants for the destruction of nicotine were found to be [Formula: see text] s-1and [Formula: see text] s-1for ES1 and SM1 cigarettes respectively. In addition, the amount of nicotine evolved by ES1 cigarette was ~10 times more than the amount of nicotine released by SM1 cigarette.
  
  
  CONCLUSIONS
  The suggested mechanistic model for the formation of pyridine from the thermal degradation of nicotine in tobacco has been found to be agreement with the kinetic model proposed in this investigation. Consequently, the concentration of radical intermediates of tobacco smoke such as pyridinyl radical can be determined indirectly from a set of integrated rate laws. This study has also shown that different cigarettes can yield varying amounts of nicotine and pyridine depending on the type of cigarette primarily because of potential different growing conditions and additives introduced during tobacco processing. The activation energy of nicotine articulated in this work is consistent with that reported in literature.Graphical abstractThe anatomy of tobacco cigarette and the major chemistry involved during combustion (pyrolysis, GC-MS analysis, and kinetic modeling).
authors: Department of Chemistry, Egerton University, P.O Box 536, Egerton, 20115 Kenya.
authors: Joshua
authors: J
authors: Kibet
authors: Department of Chemistry, Egerton University, P.O Box 536, Egerton, 20115 Kenya.
authors: Caren
authors: C
authors: Kurgat
authors: Department of Physics, University of Eldoret, P.O Box 1125, Eldoret, 30100 Kenya.
authors: Samuel
authors: S
authors: Limo
authors: Department of Chemistry, Egerton University, P.O Box 536, Egerton, 20115 Kenya.
authors: Nicholas
authors: N
authors: Rono
authors: Department of Chemistry, Egerton University, P.O Box 536, Egerton, 20115 Kenya.
authors: Josephate
authors: J
authors: Bosire
keywords: Kinetic modeling; Nicotine; Puff time; Rate of destruction