tailieunhanh - Ebook Principles of instrumental analysis (6th edition): Part 2

The book's updated material enhances its proven approach, which places an emphasis on the theoretical basis of each type of instrument, its optimal area of application, its sensitivity, its precision, and its limitations. | Molecular Mass Spectrometry ass M spectrometry is perhaps widely applicable the most of all the analytical tools available in the sense that the technique is capable of providing information about (1) the elemental composition matter; (2) the structures of samples of of inorganic, organic, and biological molecules; (3) the qualitative titative composition of complex mixtures; structure and composition and quan- (4) the of solid sUlfaces; and (.5) isotopic ratios of atoms in samples. We have already discussed in Chapter 11 how mass spectrometry is used by chemists for the identi- fication and quantitative determination of one or more elements in a sample of matter. This chapter is devoted to describing how mass spectrometry and (3) in the previous paragraph. scribes how mass spectrometry is used listed in items (2) to obtain the t)pe of information Chapter 21 de- is employed for elu- cidating the structure and composition of sUlfaces. Finally, in Section 32D, the use of isotopic ratios determined r::i'l by mass spectrumetl)' is disCl1s.,ed. Throughout this chapter, this logo indicates ~ an opportumty for online self-study at www ., linking you to interactive tutorials, simulations, and exercises. Th~ first gen~ral application of molecular mass spectrometry for routine chemical analvsis occurred in the early 19405. when the techniyues' began to be adopted by the petroleum industry for the quantitative analysis of hydrocarbon mixtures produced in catalytic crackers. Before this time, analvses of mixtures of this type, which often contained a's many as nine hydrocarbon components, were carried out by fractional distillation followed by refractive-index measurements of the separated components. Typically. 2n() hours or more of operator time was reyuired to complete an analysis. It was found that similar information could be obtained in a few hours or less with a mass spectrometer. This improved efficiency .