Formation of selected toxicants from tobacco under different pyrolysis conditions

Abstract

The effects of temperature, atmosphere, sample and particle size were examined on the formation of selected smoke compounds from tobacco. The study used on-line pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and off-line pyrolysis experiments in a pyrolyzer with subsequent GC/MS measurements. The Py-GC/MS experiments were carried out in helium, while the experiments with off-line analysis were made in nitrogen as well as in a mixture of 2% (v/v) O 2 and 98% (v/v) N 2. Two different blends of tobacco (Virginia and Burley) and some precursor compounds (cellulose, quercetin dihydrate, chlorogenic acid hemihydrate) were examined. The formation of 1,3-butadiene, benzene, naphthalene, phenol, hydroquinone and catechol were studied at 450, 600 and 900 °C. It was found that the formation of butadiene, benzene and naphthalene was promoted, while phenol formation was hindered by the introduction of 2% oxygen. The results verified that cellulose and polyphenols are source compounds of butadiene, benzene and naphthalene at 900 °C. The polyphenols may be considered as precursors of catechol, and chlorogenic acid as a precursor of hydroquinone at lower temperatures (<600 °C). The yields of the studied compounds at varied pyrolysis temperatures showed similar trends independently of the sample size. It was found that the particle size did not modify significantly the formation of the selected pyrolysis products. This does not mean, however, that the sample and particle sizes do not affect the thermal decomposition processes. To clarify this, thermogravimetric studies (TGA) were carried out at low sample masses (0.4–2 mg) in an inert atmosphere as well as in the presence of 2 and 9% oxygen.