CORESTA Meeting, Smoke/Technology, Innsbruck, 1999, ST18

Aspects of the thermal behavior of nicotine and its salts with carboxylic acids

Philip Morris USA, Richmond, VA, USA
Nicotine transfer to the gas phase from pure nicotine, nicotine carboxylic acid salts ( i.e ., protonated nicotines), and Burley tobacco was studied by thermogravimetric/differential thermal analysis/mass spectroscopy (TG/DTA/MS). Under conditions used in this study, transfer of nicotine to the gas phase occured maximal at circa 110-125°C for both nicotine and nicotine acetate, circa 160-210°C for nicotine malates, circa 195-210°C for nicotine bis (hydrogen-(2 R ,3 R )-tartrate), and circa 160-220°C for burley tobacco. Separate thermolysis experiments (at heating rates of about 400°C/min under a flow of air) afforded 92-94% yields of recovered nicotine from its salts with carboxylic acids. Under the same conditions, pure nicotine was transferred in yields of ca. 97%. It is concluded that nonprotonated nicotine and salts of nicotine with natural tobacco carboxylic acids will transfer nicotine to smoke with comparable yields and efficiencies during the smoking process. Co-pyrolysis of both nicotine and these salts with urea had little effect on nicotine recoveries. In contrast, co-pyrolysis of the nicotine salts with diammonium phosphate significantly reduced the yields of recovered nicotine. Most pyrolysis experiments reported in the literature involve inserting the substrate(s) into a preheated region. Such experiments have been used over the years as models for cigarette smoke formation. The experimental design herein involves heating the substrates from ambient to higher temperatures under gas flow. This allows any volatile products to escape pyrolytic destruction by distillation into a cooler environment before exposure to higher temperatures, a process in closer similarity to the behavior within a puffing cigarette. The temperatures required to transfer nicotine to the gas phase from its protonated forms, such as found in tobacco, are lower than the decomposition temperature of the nicotine superstructure. In contrast the superstructure of protonated forms of some other alkaloids decompose thermally at temperatures lower than the temperatures required to effect their deprotonation and/or evaporation.