Sample preparation for inorganic

Data Sheet B Sample Preparation for Inorganic Analysis... 

Sample preparation for the common desorption/ionisation (DI) methods varies greatly. Films of solid inorganic or organic samples may be analysed with DI mass spectrometry, but sample preparation as a solution for LSIMS and FAB is far more common. The sample molecules are dissolved in a low-vapour-pressure liquid solvent - usually glycerol or nitrobenzyl alcohol. Other solvents have also been used for more specialised applications. Key requirements for the solvent matrix are sample solubility, low solvent volatility and muted acid - base or redox reactivity. In FAB and LSIMS, the special art of sample preparation in the selection of a solvent matrix, and then manipulation of the mass spectral data afterwards to minimise its contribution, still predominates. Incident particles in FAB and LSIMS are generated in filament ionisation sources or plasma discharge sources. 

Gaseous and volatile compound analysis is covered in Chapter 7. Since all MS systems ultimately require gas phase ions, such a topic is of high importance in inorganic as well as molecular MS analysis. The chapter is short, yet does cover sample preparation for volatiles as well as some important applications. This chapter is very well referenced. 

The way in which blank corrections are made can cause problems in IDMS, especially where a digestion stage has proved to be necessary during sample preparation for an inorganic analyte. There are two possible approaches that can be followed ... 

Membrane filtration can be used in sample preparation for liquid chromatography, e.g., in the ion-chromatographic determination of various inorganic anions and cations in water samples. Tubular membrane interfaces have been used for sample introduction in capillary zone electrophoresis to separate the low-molecular mass organic constituents of blood plasma. 

The object of sample preparation in inorganic analysis is to meet the requirements for a substantially trouble-free determination of the analyte. The most important of these with respect to trace analysis in any matrix include ... 

In the area of inorganic constituents, the determination of nitrite/nitrate [391] and iodide [392] is very important The sample preparation for instant milk is the same as that described above for milk products. As an example, Figure 10.247 shows the separation of nitrite and nitrate in an instant baby food sample. As can be seen from this chromatogram, again both analytes are completely separated from matrix components. Precision, recovery rates, and detection limits are at a similar level as discussed for milk products. 

SEM requires little sample preparation for metallic and inorganic materials as the information required concerns only the surface structure and the material composition of the layer proximate to the surface. Small samples of up to several millimetres and sometimes even larger can be investigated directly in the SEM if the sample material has a sufficiently high electric conductivity to prevent charging produced by electron bombardment. However,... 

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