Electronic configuration of the elements to radon

This appendix describes briefly the dissolution procedures for some of the more common inorganic sample types. The use of an internal standard is discussed in Section 13.3. 

Water samples are amongst the simplest to prepare, simply requiring acidification to keep the sample elements in solution and to matrix-match with the calibration solutions, and the addition of an internal standard. The procedure is as follows. 

Open vessel digestion (HN03) for bones, teeth, hair, and soil This is a standard preparation for most organic samples. In the case of soils, nitric acid will not fully dissolve all of the sample, but this method is sufficient to examine the total available elements. 

Open vessel digestion (HF HC104) for ceramics, glass, rocks, and soil These acids should completely dissolve most materials. HF removes the silica (as volatile SiF4), which reduces the total dissolved solid content and therefore reduces interferences, and C104 produces perchlorates, which are soluble (but explosive if dried out). The use of hydrofluoric and perchloric acids therefore has considerable safety risks and requires specialized fume hoods, handling equipment, and safety equipment. The hydrofluoric and perchloric acids are removed by a later evaporation stage unless the analytical instmment and safety considerations have been specially adapted. 

Closed vessel microwave digestion for bones, teeth, hair, and soil Specially designed closed pressurized Teflon vessels may be used for microwave digestion. Teflon is transparent to microwaves, which enhances the effect of the acids by raising the temperature and pressure within the vessel. In addition the closed vessels will retain any volatile components (e.g., Si) in solution. It must, however, be emphasized that any sealed vessels must only be heated if they have been designed for the purpose. Examples of applications include Kingston and Walter (1992), Baldwin et al. (1994), Sheppard et al. (1994), and Tamba et al. (1994). 

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