Influence of potassium on the formation of benzo[a]pyrene in tobacco pyrolysis
It is known that potassium, which is the most abundant alkali metal in tobacco leaves, affects the thermal degradation of biomass and cigarette combustion. However, there is little information on the relationship between potassium and the formation of benzo[a] pyrene (B[a]P) from tobacco. In this study, tobacco samples with various potassium contents were pyrolyzed using an infrared image furnace to evaluate their B[a]P yields, and their pyrolysis behaviors were investigated by thermogravimetric analyses (TGA). Potassium-extracted samples were prepared by washing tobacco samples with water, and potassium-added samples were prepared by adding potassium lactate, potassium carbonate (K2CO3) and potassium chloride (KCl) to individual tobacco samples. It was found that the removal of potassium by water extraction increased the yield of B[a]P significantly. However, the influence of potassium addition on the yield of B[a]P was different according to the types of salts and tobacco. The addition of potassium lactate or K2CO3 to flue-cured tobacco decreased the yield of B[a]P, while the KCl addition increased it. The addition of potassium lactate to Burley tobacco did not decrease the yield of B[a]P. As the results of the TGA, the addition of potassium lactate or K2CO3 to flue-cured tobacco lowered the temperature at which cell wall components such as cellulose and lignin decomposed. On the other hand, no significant change in temperature was observed in the case of the KCl addition to flue-cured tobacco and for the addition of potassium lactate to Burley tobacco. These results indicate that the modification of the pyrolysis process of cell wall components by potassium influences the formation of B[a]P and the influence of potassium depends on the form of potassium that is present.