The form of nicotine in tobacco. Thermal transfer of nicotine and nicotineacid salts to nicotine in the gas phase

Thermal transfer to nicotine in the gas phase from neat nicotine, from vari ous nicotine carboxylic acid salts, and from endogenous nicotine in Burley, Bright, and Oriental tobacco samples has been examined by thermogravimetri c/differential thermal analysis/mass spectroscopy and evolved gas analysis. Under the conditions used in these studies, the peak transfer temperatures of these substances to nicotine in the gas phase are nicotine and nicotine acetate, both ca. 110-125 degrees C; nicotine malates, ca. 110-210 degrees C for nicotine to malic acid ratios of 1:0.56 and 1:1 and ca. 160-210 degr ees C for a nicotine to malic acid ratio of 1:2; (S)-nicotine bis[(2R,3R)-h ydrogen tartrate] dihydrate, ca. 195-210 degrees C; and tobacco samples, a range of ca. 160-220 degrees C. These results suggest that nicotine is most ly protonated in tobacco leaf. In all cases, the temperature of the transfe r of nicotine to the gas phase was found to be many hundreds of degrees bel ow the temperatures observed around the coal of a burning cigarette (smolde r, ca. 500-775 degrees C; dynamic smoking, 600 to over 950 degrees C). With in the narrow zone of a puffing cigarette that encompasses an intermediate temperature range (125-250 degrees C), kinetic data suggest that these temp eratures are not sufficient to volatilize significant amounts of nonprotona ted nicotine, assuming any exists at all, during the short puff duration (2 s). It is concluded that nonprotonated nicotine and protonated nicotine (s alts of nicotine with natural tobacco carboxylic acids) will transfer nicot ine to smoke with comparable yields and efficiencies during the smoking pro cess.