Isotope dilution microwave digestion

The apphed pretreatment techniques were digestion with a combination of acids in the pressurized or atmospheric mode, programmed dry ashing, microwave digestion and irradiation with thermal neutrons. The analytical methods of final determination, at least four different for each element, covered all modern plasma techniques, various AAS modes, voltammetry, instrumental and radiochemical neutron activation analysis and isotope dilution MS. Each participating laboratory was requested to make a minimum of five independent rephcate determinations of each element on at least two different bottles on different days. Moreover, a series of different steps was undertaken in order to ensure that no substantial systematic errors were left undetected. 

Joining another type of ancillary device to ICP-MS, Beary et al. developed a continuous-flow microwave digestion apparatus for isotope dilution analysis of lead in environmental samples [38]. Although introduction to the ICP torch was... 

Today, ICP-MS permits very low detection limits (0.1 jgkg ) of tin in biological matrices. Sample preparation consists of reconstitution of the freeze-dried material or in microwave digestion, both followed by dilution in a solution of an internal standard (europium, indium, scandium, etc.) The main characteristic isotopes used for the determination of tin are Sn, Sn, Sn, and Sn. 

After microwave-assisted digestion of the sample with a mixture of nitric acid and hydrogen peroxide, during which equilibration with the isotopically enriched spikes added also took place, formic acid was used to convert the isotope-diluted elements into volatile compounds in a photo-reactor. In the case of iron and nickel, the corresponding volatile carbonyl compounds are most likely formed, whereas in the case of selenium, hydride compounds are obtained. A schematic representation of the UV-PVG-ICP-IDMS setup is shown in Figure 8.10. The good accuracy of results was demonstrated by the successful analysis of certified reference materials. Extremely low LODs of 0.18, 1.0, and 1.7 pgg were found for Ni, Fe, and Se, respectively, which are improvements of a factor of 30 for the two metals and 150 for Se compared with conventional pneumatic solution nebulization. 

Beary, E. S., Paulsen, P. J.,Jassie, L. B., and Fassett,J. D. (1997). Determination of environmental lead using continuous-flow microwave digestion isotope dilution inductively coupled plasma mass spectrometry. Anal. Chem. 69(4), 758. 

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