Inorganic analytical methods

Different analytical methods used for the analysis of samples collected under the requirements of different environmental laws are discussed in Chapter 2.4. Although many of these methods target the same analytes, their calibration requirements are different. Tables 4.5, 4.6, and 4.7 summarize the differences in calibration requirements for organic compound and trace element analysis. (Inorganic analyte methods and techniques have a range of requirements that cannot be summarized in a concise manner we should refer to specific methods for this information). 

Total attack is generally aoeomplished by using hydrofluoric acid in oombination with other aoids that allow all sample components except silica, which is volatilized during evaporation to dryness, to be solubilized. Some other components (e.g. boron) may be partially lost. This type for treatment is exclusive for inorganic analytes. Methods using this prooedure are best validated with CRM. 

Kruszynski, A.J. and A. Henriksen Die quantitative Bestimmung von Kohlenmonoxid im Tabakrauch [The quantitative determination of carbon monoxide in tobacco smoke] Beitr. Tabakforsch. 5 (1969) 9-12. Kubota, H., M.R. Guerin, and J.A. Carter Inorganic analytical methods of tobacco smoke analysis A comparative smdy 26th Tobacco Chemists Research Conference, Program Booklet and Abstracts, Vol. 26, Paper No. 23, 1972, p. 35. 

Although many quantitative applications of acid-base titrimetry have been replaced by other analytical methods, there are several important applications that continue to be listed as standard methods. In this section we review the general application of acid-base titrimetry to the analysis of inorganic and organic compounds, with an emphasis on selected applications in environmental and clinical analysis. First, however, we discuss the selection and standardization of acidic and basic titrants. 

Inorganic Analysis Redox titrimetry has been used for the analysis of a wide range of inorganic analytes. Although many of these methods have been replaced by newer methods, a few continue to be listed as standard methods of analysis. In this section we consider the application of redox titrimetry to several important environmental, public health, and industrial analyses. Other examples can be found in the suggested readings listed at the end of this chapter. 

The determination of an analyte s concentration based on its absorption of ultraviolet or visible radiation is one of the most frequently encountered quantitative analytical methods. One reason for its popularity is that many organic and inorganic compounds have strong absorption bands in the UV/Vis region of the electromagnetic spectrum. In addition, analytes that do not absorb UV/Vis radiation, or that absorb such radiation only weakly, frequently can be chemically coupled to a species that does. For example, nonabsorbing solutions of Pb + can be reacted with dithizone to form the red Pb-dithizonate complex. An additional advantage to UV/Vis absorption is that in most cases it is relatively easy to adjust experimental and instrumental conditions so that Beer s law is obeyed. 

Noncatalytic Reactions Chemical kinetic methods are not as common for the quantitative analysis of analytes in noncatalytic reactions. Because they lack the enhancement of reaction rate obtained when using a catalyst, noncatalytic methods generally are not used for the determination of analytes at low concentrations. Noncatalytic methods for analyzing inorganic analytes are usually based on a com-plexation reaction. One example was outlined in Example 13.4, in which the concentration of aluminum in serum was determined by the initial rate of formation of its complex with 2-hydroxy-1-naphthaldehyde p-methoxybenzoyl-hydrazone. ° The greatest number of noncatalytic methods, however, are for the quantitative analysis of organic analytes. For example, the insecticide methyl parathion has been determined by measuring its rate of hydrolysis in alkaline solutions. 

Chemical Properties. Elemental analysis, impurity content, and stoichiometry are determined by chemical or iastmmental analysis. The use of iastmmental analytical methods (qv) is increasing because these ate usually faster, can be automated, and can be used to determine very small concentrations of elements (see Trace AND RESIDUE ANALYSIS). Atomic absorption spectroscopy and x-ray fluorescence methods are the most useful iastmmental techniques ia determining chemical compositions of inorganic pigments. Chemical analysis of principal components is carried out to determine pigment stoichiometry. Analysis of trace elements is important. The presence of undesirable elements, such as heavy metals, even in small amounts, can make the pigment unusable for environmental reasons. 

F E Beamish and A D Westland, Volumetric and gravimetric analytical methods for inorganic compounds, Anal. Chem., 1960, 32, 249R... 

An extremely wide variety of analytical methods are used by RM producers and developers in the certification of RMs for inorganic elemental content. These methods range from the classical, through current instrument based methods to highly specialized definitive methods. 

How critically interdependent matrix and analytical methods can be is illustrated in the example of the analysis of a soil sample. Table 7.1 shows the method dependent certified values for some common trace elements. The soil had been subjected to a multi-national, multi-laboratory comparison on a number of occasions (Houba et al. 1995) which provided extensive data. The data was subjected to a rigorous statistical program, developed for the USEPA by Kadafar (1982). This process allowed the calculation of certified values for a wide range of inorganic analytes. Uniquely, for the soil there are certified values for four very different sample preparation methods, as follows ... 

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