Amalgams mercury vapour release

Parsons et al.66 reported on the determination of total mercury as a toxic element in urine at the trace level using ICP-MS. The main sources of exposure in the human body are inhalation of Hg vapour released from dental amalgams and the consumption of fish species that accumulate, for example, methyl mercury (MeHg). 

Elemental mercury (Hg°) is a naturally occurring form of the metal that exists uniquely in liquid form at room temperature and quickly turns to vapour when heated. The natural sources of Hg° in the environment include the release of Hg gases from volcanic eruptions and the erosion of ores that contain Hg. Several studies over the past 30 years have demonstrated that dental amalgam filling releases mercury vapour into the oral cavity. Mouth breathing carries the vapour to the lung where it is absorbed and distributed to tissues. 

By use of an amalgamation step, a decrease in the sample matrix effect upon the instrument calibration (e.g. due to varying release rates for mercury and unspecific UV absorption) can be expected. Thus, calibration may be carried out by use of standards without the sample matrix present, provided that the overall release of mercury is as complete from the sample as from the standard. Further, a high calibration precision by use of known amounts of mercury vapour was reported by Dumarey et al. (1985) and Friese et al. (1990). The latter group reported results for different biological reference samples in close agreement with certified values. 

Sensitivity and reproducibility is improved if the mercury vapour formed is concentrated by the formation of amalgams on gold wool. Heating the gold wool causes the mercury to be released suddenly and it may then be measured. This can improve sensitivity by at least a factor of 10. 

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