Environmental and Other Applications

Recently, several new methods have been developed for measuring isotope ratios in elemental spedes of some real-world samples, standards, and reference materials using chromatographic separation coupled on-line to MC-ICP-MS. So far, there are about 15 published papers which describe the application of on-line chromatography coupled with MC-ICP-MS to isotopic analysis in elemental species of Hg, Pb, S, Sb, Cl, and Br. In this section, these applications, induding sample preparation, analytical charaderistics of the technique, instrumentation, spedes and isotopes monitored, and some useful results, are discussed. 

GC has been used for the separation of Hg spedes and MC-ICP-MS to measure Hg isotope ratios. Krupp and Donard [11] coupled capillary GC with different MC-ICP-MS instruments via a home-made transfer line for the measurement of the Hg isotope ratios in two Hg species, Meng and IHg (Table 17.1). A T1 standard was added continuously to the plasma by using a T-piece for the cormection of the GC unit and the spray chamber with the plasma torch. The five most abundant Hg isotopes were measured simultaneously in the SPEX (IHg + spedes) and STREM (MeHg+ species) mercury standards. These spedes were first derivatized to Et2Hg and EtMeHg, respectively. Then the species were separated from one another using GC and introduced diredly into the MC-ICP-MS instrument, with which isotope ratios were measured based on the short transient signals obtained. 

Dzurko et al. [12] determined compound-spedfic Hg isotope ratios using GC interfaced with MC-ICP-MS (Table 17.1). The procedure consists of (i) species extraction based on ethylation, followed by preconcentration of the species thus obtained on a Tenax trap, (ii) thermal desorption of these Hg species and separation using a home-made GC unit, and (iii) registration of the isotope ratios in Hg species using a Neptune MC-ICP-MS instrument. Thallium was introduced 

In a subsequent investigation, the same group [14] utilized the technique developed to study spedes-specific stable isotope fractionation of mercury during methylation of IHg by anaerobic bacteria Desulfobulbus propionicus) in the dark (Table 17.1). The isotopic composition of Hg in IHg and MeHg species was measured on-line from the same sample. The authors demonstrated mass-dependent fractionation of Hg isotopes during the experiment. 

Organolead compounds are pollutants in air, water, soil, and sediments. The toxicity of organolead species depends on the organic groups bound to the Pb atom. Lead has four stable isotopes ( Pb, Pb, Pb, and Pb) and isotopic analysis of Pb can be used for geological dating and to track environmental processes and sources of Pb species. 

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