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CORESTA Meeting, Smoke Science/Product Technology, 2011, Graz, ST 25

Chemical, physical and thermodynamic evaluation of arsenic species and their transformation during cigarette smoking

LIU C.(1); TAEBUNPAKUL S.(2); GOENAGA-INFANTE H.(2); BRAYBROOK J.(2); HU J.(1); WRIGHT C.G.(1); McADAM K.G.(1)
(1) British American Tobacco, Group R&D, Southampton, UK; (2) LGC Ltd, Teddington, Middlesex, UK

Tobacco smoke contains metals such as chromium (Cr), cadmium (Cd) and arsenic (As). The levels of Cr, Cd and As in mainstream cigarette smoke normally range from a few to a few tens of parts-per-million (ppm) in modern filtered cigarettes. The toxicity of these metals is specific to their chemical forms as well as their concentrations in cigarette smoke. It has also been noted in the literature that redox properties of these metal species are also an important factor to consider because of their potential to mediate free radical reactions in cigarette smoke. Very little speciation information exists for these metals either in tobacco samples or in cigarette smoke. Moreover, it is desirable to understand their transformation during the smoke formation processes under puffing and smouldering cycles. In this study, we combined analytical chemistry (HPLC-ICP-MS), synchrotron-based X-ray Absorption Near-Edge Structure Spectroscopy (XANES) and thermodynamic prediction to elucidate the transformation reactions of As species during the mainstream smoke formation process. XANES results revealed a dynamic transformation from As(V) in 3R4F tobacco leaf to As(III) species in fresh mainstream smoke, although the exact species involved in the reactions cannot be determined due to the detection limit of the technique. The direction of this redox reaction was reversed upon smoke ageing. Using HPLC-ICP-MS, percentages of the water-soluble As species in cut tobacco and the mainstream smoke have been identified and they included species such as methylarsonic acids (DMA, MMA) and arsenobetaine (AsB). In addition, the chemical analysis on fresh and aged smoke samples confirmed the As(III) and As(V) redox reaction, thus allowing for a consistent picture to be built for the dynamic transformation of As species during smoke formation.