Chapters Microwave digestion

Direct your Web browser to http //chemistry.brookscole.com/skoogfac/. From the Chapter Resources menu, choose Web Works. Locate the Chapter 36 section, and find the links for microwave digestion systems. Look up information on open-vessel microwave digestion systems versus closed-vessel systems. Summarize the advantages and disadvantages of these two approaches. 

Figure 8. Photograph of the fully automated total Tc analyzer instrument in the laboratory. The labeled components are (A) robotic autosampler (B) microwave digestion unit (C) fluid handling components for sample injection, automated standard addition, sample acidification/digestion (D) separation fluidics including syringe pumps, flow reversal, and diversion valves (E) separation column (F) flow scintillation detector and (G) control computer with automation software. Reproduced with permission from the Handbook of Radioactivity Analysis, Second Edition Chapter 14, page 1152. Copyright...

Most AdSV determinations are carried out, after sample digestion by UV irradiation, by recording cathodic stripping voltammograms. Oxidative microwave digestion with Oxisolv (Chapter 25.5) is also suitable for sample preparation. Only rarely can trace concentrations of metals in natural samples such as seawater be determined without sample digestion. An example is the determination of... 

As mentioned above, the development of microwave-oven engineering has allowed a drastic enhancement of safety and reproducibility. Several ovens dedicated to chemistry are now available. For further details, the reader can referred to the paper from Kremsner et al In the second part of this chapter, different compounds have been synthesized using an advanced microwave oven from the CEM Corporation (Figure 2.1). The oven is a MARS-5 Microwave Digestion System operating at a frequency of 2.45 GHz and a maximum power of 1200 W. The reactor used (XP-1500 plus model) can operate up to 220 C and 55 bars as internal pressure. To prevent explosion, any deviation in the predetermined parameters causes the system to stop. Secondly, in case of overpressure, the breaking of a disk occurs and the released gaseous species are evacuated by the... 

Antigen partly destroyed or masked by fixation If the antigen was masked as a result of overfixation in formalin, the nse of digestion or microwave heating prior to the application of the primary antibody may increase staining intensity (see Chapter 13). 

It should be noted that microwave-assisted extraction (MAE) discussed in this chapter is different from microwave-assisted acid digestion. The former uses organic solvents to extract organic compounds from solids, while the latter uses acids to dissolve the sample for elemental analysis with the organic contents being destroyed. Microwave-assisted digestion of metals is covered in Chapter 5. 

Another application area in microwave technology is the use of microwave irradiation for the enzymatic digestion of proteins [106]. As discussed in the early part of this chapter, enzymatic cleavage to produce smaller peptide fragments of protein samples is an important step in structural characterization of proteins [24]. Traditional enzymatic digestion method usually takes several hours, whereas microwave-assisted digestion occurs in minutes. The initial... 

Some contradictory results are obtained in the comparison of results in the determination of arsenic after ultrasonic slurry sampling — the use of sampling is not most appropriate in this case as the sampling step is before the slurry formation — ultrasound-assisted extraction — leaching has been the correct word in this case — and microwave-assisted digestion [28], which will be treated in detail in Chapter 5. 

This chapter describes the principal applications of microwaves to the pretreatment of solid samples, with special emphasis on digestion and extraction, which are their two main uses in analytical chemistry. The description is preceded by a discussion of the fundamentals of microwave energy and its interaction with matter, and also of the equipment used by analytical laboratories, which can be of the open or closed type depending on whether they operate at atmospheric pressure or a higher level and whether they use multi-mode or focused microwaves. Selected designs developed for specific purposes are also commented on. 

The addition of auxiliary components to perform specific steps, such as titration and microwave-assisted sample digestion, also influences sample dispersion, and is discussed in the subsequent chapters. 

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