Simultaneous Determination of Mercury and Tin Species in Standard Reference Materials

Methods applicable to the extraction and quantification of mercury and tin species in biological, environmental, and clinical reference materials using speciated isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SID-GC/ICP-MS) have been developed and optimized. These methods were applied to measurement of methylmercury; inorganic mercury; and mono-, di-, and tributyltin species in various biological-matrix SRMs.

Tributyltin (TBT) as well as its degradation products dibutyltin (DBT) and monobutyltin (MBT) are toxic compounds widely dispersed in the environment. TBT has been extensively used as a biocide in marine antifouling paints since the 1970s and subsequently released into the marine environment, resulting in extensive damage to organisms such as oysters and mussels. In the case of mercury, the environmental and human health effects are generally related to the environmental transformation of inorganic mercury (iHg) to methylmercury (MeHg), and subsequent bioaccumulation of methylmercury in wildlife and humans. In some cases, more than 90 % of the total mercury found in edible fish tissue is in the form of methylmercury. The potential for human and environmental impacts calls for improvements in current analytical methods to obtain accurate measurements for specific organometallic species.

Listed below are SRMs that are currently available with values assigned for mercury or tin species. In most cases, these SRMs are certified for mercury species at various concentrations and in both freeze-dried and fresh frozen forms, which represent different analytical challenges. The methylmercury, inorganic mercury, and total mercury in the various materials have been determined, in most cases, by ID GC/ICP-MS and GC/MS methods performed by NIST and additional measurements by collaborating laboratories. The methods utilized different sample extraction, cleanup, separation, instrumental techniques, and approaches to quantification. These materials are provided primarily for use in method development and as control materials to support the measurement of these constituents in other similar products. These materials will help ensure comparability and accuracy of organometallic speciation measurements in biota and clinical matrices. The development of SRMs for organometallic species is an ongoing effort and will soon include the first fresh frozen mussel tissue certified for butyltin species.   

Major Accomplishments:

• Eight natural-matrix SRMs have been produced with values assigned for methylmercuryAnalytical methods have been developed for the quantification of methylmercury, inorganic mercury, monobutyltin, dibutyltin, and tributyltin.