Mercury reference materials

Meija, J., Yang, L., Sturgeon, R.E., and Mester, Z. (2010) Certification of natural isotopic abundance inorganic mercury reference material NlMS-1 for absolute isotopic composition and atomic weight. J. Anal. At. Spectrom., 25, 384-389. 

Donais MK, Saraswati R, Mackey E, Vangel MG, Levenson MS, Mandic V, Azemard S, Hor-VAT M, Burow M, Emons H, Ostapczuk P, and Wise SA (1997) Certification of three mussel tissue Standard Reference Materials (SRMs) for MeHg and total mercury content. Fresenius J Anal Chem 358 424-430. 

Horvat M, Liang L, Azemaed S, Mandic V, Coquery M, and Viixeneuve J.-P (1997) Certification of total mercury and methylmercury concentrations in mussel homogenate (Mytilus edidis) reference material, IAEA-142. Fresenius J Anal Chem 358 411-418. 

Quevauviller Ph, and Maier EA (1999) Interlaboratory studies and certified reference materials for environmental analysis - the BCR approach. Elsevier, Amsterdam Quevauviller Ph, Drabaek I, Muntau H, Biahchi M, Bortoli A, and Griepink B (1996a) Certified reference materials (CRMs 463 and 464) for the quafity control of total and methyl mercury determination in tuna fish. Trends Anal Chem 15 160-167. 

Gill and Fitzgerald [481] determined picomolar quantities of mercury in seawater using stannous chloride reduction and two-stage amalgamation with gas-phase detection. The gas flow system used two gold-coated bead columns (the collection and the analytical columns) to transfer mercury into the gas cell of an atomic absorption spectrometer. By careful control and estimation of the blank, a detection limit of 0.21 pM was achieved using 21 of seawater. The accuracy and precision of this method were checked by comparison with aqueous laboratory and National Bureau of Standards (NBS) reference materials spiked into acidified natural water samples at picomolar levels. Further studies showed that at least 88% of mercury in open ocean and coastal seawater consisted of labile species which could be reduced by stannous chloride under acidic conditions. 

Schintu, M., F. Jean-Caurant, and J.C. Amiard. 1992. Qrganomercury determination in biological reference materials application to a study on mercury speciation in marine mammals off the Faroe Islands. Ecotoxicol. Environ. Safety 24 95-101. 

The certification procedure for seven trace metals (Ba, Ca, Li, Mg, Mn, Na and Sr) in the certified reference material FEBS-1 (National Research Council Canada, Institute for National Measurement Standards, Ottawa, Canada) based on fish otolith matrix by isotope dilution - ICP-MS in comparison to ICP optical emission spectrometry and X-ray fluorescence analysis, is described by Sturgeon et al4X The isotope dilution technique is also employed for species analysis in biological systems,46 e.g., for the determination of mercury species in tuna material,54 or in aquatic systems using cold vapour ICP-MS.55... 

In November 1971, NBS issued Standard Reference Material (SRM) 1630, Mercury in Coal, with a provisionally certified mercury content of 0.13 ppm. Later the provisional value of 2.1 ppm selenium in SRM 1630 was issued. 

For a trace element concentration to be certified by NBS, it must be determined by at least two independent methods, the results of which must agree within a small experimental error range of 1% to 10%, depending on the nature of the sample and the concentration level of the element. Such accuracy in determining some trace elements for certification of coal SRM is achieved most easily by NAA with radiochemical separation. Scientists at NBS have extensively tested a neutron activation method that involves a combustion separation procedure on coal as well as on several other matrices to be certified as standard reference materials. The procedures they have thus developed to determine mercury (12), selenium (13), and arsenic, zinc, and cadmium (14) are outlined in a following section on methods for determining specific elements in coal. 

Alberts, J.J., Takacs, M. and Pattanayek, M. (2001) Influence of IEfSS standard and reference materials on copper and mercury toxicity to Vibrio fischeri, Acta Hydrochimica et Hydrobiologica 28, 428-435. 

The calibration step is critical. In general, the basic principle is always to use two independent calibration solutions. One of these can be made from pure chemicals, for example, Hg° dissolved in concentrated HN03 and diluted to the appropriate volume. For mercury, commercially available standard solutions can be used, but regular checks against a reference standard must be made. Certified reference materials (CRFs) should be used if available, but reference standards can also be prepared from pure mercury compounds. In the absence of aqueous-phase reference standards, solid materials may be used. 

I. R. Pereiro, A. Wasik, R. -obin ski, Determination of mercury species in tish reference materials by isothermal multicapillary gas chromatography with atomic emission detection after microwave-assisted solubilization and solvent extraction, J. Anal. Atom. Spectrom., 13 (1998), 743D747. 

Further barriers to a broader use of Raman spectroscopy are problems with intensity calibration and benchmarking, lack of reference materials, and the expense of the equipment. The calibration equipment, which is typically supplied with the instruments by the manufacturers, varies for instance neon or mercury lamps are delivered with dispersive instruments and HeNe lasers with FT spectrometers. 

Numerous standard or certified reference materials exist for verifying the reliability of new or modified methods, especially for total mercury standard reference materials for individual organomercury species can be more difficult to obtain. The existing methods for determining mercury in biological and environmental matrices are described more fully in the following sections. 

Padberg S, Burow M, Stoeppler M. 1993. Methyl mercury determination in environmental and biological reference and other materials by quality control with certified reference materials (crms). Fresenius J Anal Chem 346 686-688. 

Seawater and estuarine water CRMs certified for their contents of trace elements (see sections 8.7 and 8.8) were not analysed for mercury. Due to the high volatility of mercury, water to be analysed for Hg content can not be stored in polythene bottles and a higher acidification is necessary. So far, no CRM existed for this element, and hence a separate reference material had to be produced. 

The preparation of a seawater candidate reference material to be certified for its content in mercury poses additional difficulties in comparison to other trace metals. 

---