Organic compound analysis principle

GC-C-IRMS instrumentation enables the compound-specific isotope analysis of individual organic compounds, for example, n-alkanes, fatty acids, sterols and amino acids, extracted and purified from bulk organic materials. The principle caveat of compound-specific work is the requirement for chemical modification, or derivatisation, of compounds containing polar functional groups primarily to enhance their volatility prior to introduction to the GC-C-IRMS instrument. Figure 14.7 summarises the most commonly employed procedures for derivatisation of polar, nonvolatile compounds for compound-specific stable isotope analysis using GC-C-IRMS. 

Chapter 1 discusses the principles of the various techniques now being employed in the analysis of soils, sludges and sediments and the types of determinations to which these methods can be applied. This chapter also contains a useful key system which enables the reader to quickly locate in the book sections in which are discussed the determination by various techniques of particular organic compounds in particular types of sample. 

As discussed in Chapter 9.C, ambient particulate matter contains inorganic elements and ions, including trace metals, as well as graphitic (elemental) carbon and a wide variety of organic compounds and water. Techniques in common use to measure these species are discussed very briefly here. For further details of the principles behind these techniques, the reader should consult instrumental analysis texts (e.g., Skoog et al., 1998). Specific applications of various methods to particles in the atmosphere are described in the book edited by Spurny (1986) as well as the references at the end of this chapter. 

We shall not describe here the differences among several types of mass spectrometer especially designed for structural analysis of organic compounds, but shall only give general principles which are necessary for understanding how a mass spectrum arises. 

The major kinds of spectroscopy used for structural analysis of organic compounds are listed in Table 9-1. The range of frequencies of the absorbed radiation are shown, as well as the effect produced by the radiation and specific kind of information that is utilized in structural analysis. After a brief account of the principles of spectroscopy, we will describe the methods that are of greatest utility to practical laboratory work. Nonetheless, it is very important to be aware of the other, less routine, methods that can be used to solve special problems, and some of these are discussed in this and in Chapters 19 and 27. 

Organic substances that are not volatile are grouped under semivolatiles. The latter class also includes substances of very low volatility such as chlorinated biphenyls and polynuclear aromatics. As far as the GC/MS technique goes, the principle of analysis of the semivolatile organics is not so distinctly different from that of the volatile organics. On the other hand, the method of extraction of analytes from the sample matrices and the sample concentration steps for these semivolatile organic compounds vastly differ from the volatile organics. Such extraction techniques and the sample cleanup methods are discussed more extensively in Chapter 1.5. 

The book commences with a chapter in which the principles and theory of various chromatographic techniques are discussed. Ion chromatography (Chapter 2) is a relatively recently introduced technique that has found extensive applications in the analysis of mixtures of anions and to a lesser extent of organic compounds and cations. Codetermination of anions and cations is possible. A variant of ion chromatography, namely electrostatic ion chromatography has to date found a very limited application to the determination of anions and is discussed in Chapter 3. 

The thermodynamic principles introduced in Chapter 10 can be used to investigate the partitioning of organic compounds between the gas and aerosol phases. We will first focus on the analysis of a series of idealized scenarios and then discuss their applicability to the atmosphere. 

This chapter will focus on MS principles and instrumentation for both organic and inorganic analysis. Chapter 10 will cover applications of MS for organic and inorganic analyses as well as interpretation of simple mass spectra for structural identification of organic compounds. 

---