Formation of nitric oxide during tobacco oxidation.

摘要

The sources of NO during biomass oxidation, and in particular tobacco oxidation, have been disputed. Literature results range from decomposition of nitrate to the oxidation of atmospheric nitrogen. To rectify these discrepancies, this study focuses on the sources of nitric oxide (NO) during the oxidation of tobacco samples. When Burley tobacco was heated in a partially oxidized atmosphere, NO was produced at two distinct temperature ranges, namely 275-375 degrees C (the low-temperature range) and 425-525 degrees C (the high-temperature range). The formation of NO at the low-temperature range with Burley tobacco was found to be unaffected by oxygen, while the formation of NO at the high-temperature range required an oxygen atmosphere. With Bright and Oriental tobacco, NO was produced only within the higher-temperature range. To understand the formation processes and the sources of NO formation within these two temperature ranges, several endogenous nitrogenous tobacco compounds were examined. These weremixed with non-nitrogenous biomass model materials, namely cellulose, pectin, xylan, or lignin, which also occur naturally in tobacco, and the mixtures were heated in a flow tube reactor under a partially oxidative atmosphere. A commercial gas analyzer was used to monitor the formation of NO during heating. Nitrate ion was determined to be the source of NO formation in the range of 275-375 degrees C. This ion was decomposed in a carbonaceous surrounding to produce NO. For NO formation at the higher temperature range, amino acids and proteins were shown to be the sources. The interaction between nitrogenous organic compounds (amino acids and proteins) and pectin first produced a nitrogen-containing char at a temperature below 350 degrees C. Oxidation of this char at the higher temperatures produced NO.