Currently available measurement techniques quantify total arsenic but far more challenging is identifying the exact form of arsenic present.
‘Understanding the form of arsenic is important because arsenic is known to be toxic to humans, and the level of toxicity depends on, amongst other things, its chemical form,’ says Dr Kevin McAdam, Principal Scientist at British American Tobacco. ‘There is clear evidence, for example, that inorganic arsenic is carcinogenic to humans, whereas there is little evidence of carcinogenicity with arsenic compounds that cannot be metabolised in humans, such as arsenobetaine,’ he says. ‘Now for the first time, we are able to identify the exact chemical form of a number of arsenic species found in tobacco and smoke. This should allow us a greater understanding of their possible role in smoking-related diseases and potentially help us identify routes for their removal from tobacco and smoke,’ he adds. The new technique is described in the journal J. Anal. At. Spectrom .
Heavy metals, like arsenic, are thought to be absorbed naturally by tobacco plants from soil and atmospheric sources and to transfer to some degree into cigarette smoke.
Current analytical methods for total arsenic determination in tobacco leaf and smoke condensates involve the use of strong acids to efficiently extract the arsenic from the sample matrix. The amount of total arsenic present is then determined using spectroscopy or elemental mass spectrometry. However, recent synchrotron studies by scientists at British American Tobacco have shown that arsenic is present as a mixture of species in tobacco and smoke2. The new technique goes a step further to identify many of these individual arsenic species. A less aggressive extraction technique is used to ensure that arsenic species are removed from the substrates in a way that does not change their chemical form. The different species are then separated from each other using liquid chromatography and the amount of each determined using mass spectrometry.
‘Using this technique, we managed to identify 63% of the arsenic present in tobacco, and identify major species present in water soluble extracts of cigarette smoke’ says Dr McAdam. ‘Identifying the chemical forms of arsenic in tobacco products is a step forward in improving our understanding of the composition of tobacco and cigarette smoke, and this study now opens doors for us to examine other toxic metals such as cadmium, chromium, lead, nickel and selenium,’ he says.
Heidi Goenaga-Infante, Principal Scientist at LGC in Mass Spectrometry, said ‘It is particularly satisfying that LGC’s significant experience and capability in the area of arsenic and selenium speciation in plant materials has been recognised. By working closely with BAT’s scientists to understand the complex nature of a typical tobacco product, we have successfully developed a new method for determining arsenic species in tobacco and tobacco smoke.’ BAT is now extending this collaboration with LGC to identify other metal species within tobacco smoke.