Chapter 1 - Analytical chemistry deals with methods for...

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1 ¾ Analytical chemistry deals with methods for determining chemical composition of samples of matter. ¾ Qualitative method yields information about the identity of atomic or molecular species or the functional groups in the sample; ¾ Quantitative method, in contrast, provides numerical information as to the relative amount of one or more of these components. 1.A. CLASSIFICATION Of ANALYTICAL METHODS ¾ Classical methods or wet- chemical methods precede instrumental methods by a century or more. Methods Classical instrumental. Classical Methods ) Carried out by separating the components of interest (the analytes) by precipitation, extraction, or distillation. ) Qualitative analyses, the separated components are then treated with reagents that yielded products that could be recognized by their colors, their boiling or melting points, their solubility in a series of solvents, their odors, their optical activities, or their refractive indexes. ) Quantitative analyses, the amount of analyte was determined by gravimetric or by titri- metric measurements. Methods Gravimetric Titrimetric. the mass of the analyte or some compound produced from the analyte was determined the volume or mass of a standard reagent required to react completely with the analyte was measured. Classical methods for separating and determining analytes still Find use in many laboratories, The extent of their application is, however, decreasing with time and with advent or instrumental methods to supplant them.
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2 1A-2 Instrumental Methods ± Based on measuring Physical properties of analytes such as conductivity, electrode potential, light absorption or emission, mass to-charge ratio, and fluorescence. Also, Chromatographic and electrometric techniques ± Used for quantitative analysis of a variety of inorganic, organic, and biochemical analytes, ± Many of the phenomena that instrumental methods are based on have been known for a century or more. The application was delayed by lack of reliable and simple instrumentation. In fact, the growth of modern instrumental methods of analysis has paralleled the development of the electronics and computer industries. TYPES of INSTRUMENTAL METHODS Many physical characteristics are useful for qualitative or quantitative analysis. Table 1-1 lists most of the characteristic properties that are currently used for instrumental analysis.
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3 ± The first six methods involve interactions of the analyte with electromagnetic radiation where radiant energy is produced by the analyte. ± The next five involve changes in electromagnetic radiation by interaction with the sample. ± Four electrical properties then follow. ± Finally, four miscellaneous properties are grouped together: mass-to-charge ratio, reaction rate, thermal characteristics, and radioactivity. ± In addition to the numerous methods listed in Table I-I, there is a group of
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Chapter 1 - Analytical chemistry deals with methods for...

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