Microwave method

Freitag and John [96] studied rapid separation of stabilisers from plastics. Fairly quantitative extraction (>90% of the expected content) of stabilisers from a powdered polymer was achieved by MAE within 3 to 6 min, as compared to 16 h of Soxhlet extraction for the same recovery. MAE and Soxhlet extraction have also been compared in the analysis of cyclic trimer in PET [113]. On the other hand, Ganzler et al. [128] compared the extraction yields for various types of compounds from nonpolymeric matrices for microwave irradiation with those obtained by the traditional Soxhlet or shake-flask extraction methods. Microwave extraction was more effective than the conventional methods, in particular in the case of polar compounds. As expected, the efficiency of the former is high especially when the extraction solvents contain water. With the high dipole moment of water, microwave heating is more... [Pg.138]

Taylor CR, Shi S-R, Chen C, et al. Comparative study of antigen retrieval heating methods microwave, microwave and pressure cooker, autoclave, and steamer. Biotech. Histochem. 1996 71 263-270. [Pg.282]

Compared to enzyme digestion methods, microwave heating demonstrated more intense immunoreactivity of estrogen and progesterone in breast cancer tissues fixed with methacam (60% methanol, 30% chloroform, and 10% acetic acid) (Oyaizu et al., 1996). [Pg.153]

These, then, are the reasons why magnetic resonance methods, microwave or far-infrared laser, have had limited success with 2A diatomic radicals. Similar considerations apply to nonlinear polyatomic radicals in doublet states success in far-infrared laser magnetic resonance depends upon the magnitude of the spin-rotation coupling, and the size of the energy mismatch between the transition frequency and the laser frequency, since the mismatch has to be magnetically tuned. This becomes less of a limitation as more laser frequencies become available, except that one then needs to know in advance which laser frequency to choose. It becomes part of the search problem ... [Pg.641]

Liquid penetrant method Magnetic particle method Eddy current method Microwave method Radiography, including... [Pg.127]

Reference will be made in the relavant subsections to the calculations necessary for a theoretical interpretation of the results of the individual experimental methods (microwave, photoelectron spectroscopy, nmr data, etc.). [Pg.5]

Supported zeolite membranes have been prepared using numerous procedures [4] such as alignment of crystals in electrical fields, electroplating, self-assembly, growth on organic molecular layers, covalent linkages, hydrothermal synthesis (in situ and ex situ), hydrothermal method microwave heating assisted, dry gel method (vapor-phase transport method and steam-assisted crystallization), synthesis at the interface between two fluid phases, etc. [Pg.271]

Although the traditional Soxhlet and solvent extraction techniques are widely accepted, they have inherent limitations and problems. Thus, Soxhlet extraction requires 12-24 h in most cases and uses high volumes of organic solvents (hundreds of millilitres). In contrast to conventional methods, microwave-assisted extraction can reduce the extraction time to less than 30 min and solvent consumption to under 50 ml [12]. Moreover, the recoveries obtained with microwave-assisted extraction are comparable with those provided by alternative extraction methods [7]. [Pg.218]

The reaction rate doubles with every 10°C increase, so that hydrolysis at 145°C for 4 h gives results comparable to the conventional method. Microwave hydrolysis reduces analysis time to 30-45 min. Alternative hydrolysis agents include sulfonic acid, which often gives better recovery but is nonvolatile, and alkaline hydrolysis, used in the analysis of tryptophan, proteoglycans, and proteolipids. [Pg.124]

The selectivity and sensitivity offered by atomic spectroscopy techniques can be used for direct and indirect determination of metals in a range of pharmaceutical preparations and compounds. Metals can be present in pharmaceutical preparations as a main ingredient, impurities, or as preservatives which can be prepared for analysis using non-destructive (direct or solvent dilution) or destructive methods (microwave acid digestion, bomb combustion, extraction, etc.) and the metal of interest measured against standards of the metal prepared in the same solvents as the sample. Methods associated with some pharmaceutical products are already described in the international pharmacopoeias and must be used in order to comply with regulations associated with these products, e.g titration techniques are carried out according to methods that are the same for all pharmaceutical products. [Pg.230]

Tentative heat of formation was defined by MOPAC. Calculation was started from initially defaulted value of inter-atomic distance in each sample Value of gradient by root-mean-square method Microwave spectroscopy cited in [13]... [Pg.304]

This method, developed at the end of the 19th century, is still the most widely used when organic compounds have to be extracted from solid materials, like dusts, sand, soil, and marine sediments. It is particularly suitable when the organic material is strongly adsorbed on a porous solid matrix. Such a simple method presents several advantages the sample is repeatedly brought into contact with fresh portions of the solvent and no filtration is required after the leaching step, simultaneous extraction in parallel can be performed since the basic equipment is inexpensive, and finally it has the possibility to extract more sample mass than most of the latest methods [microwave extraction,... [Pg.821]

In the case of protein, heat treatment of pork does not greatly affect retention as long as the critical temperature or time is not greatly exceeded according to Sebranek (1988). This has been suggested to be about 100°C and less than 1 hr, respectively. Heating methods (microwave, steam, infra-... [Pg.136]

In the microwave synthesis of zeolites, a mixture of a precursor and a zeolite support is heated in a microwave oven. The sample is then tested for its catalytic activity and the results compared with those from the sample obtained by the conventional method. Microwave irradiation at the calcination stage led to samples with more uniform partide-size distribution and microstructure and to bimetallic catalysts with different morphology. [Pg.619]

There are numerous physical methods that can be used to determine partial molecular structures. But here we will limit our discussion to the four methods that are in wide current use and that may be utilized to accurately determine a total molecular structure. These are three diffraction methods, namely electron diffraction, neutfon diffraction, and X-ray diffraction, and one spectfoscopic method, microwave spectfoscopy. (There are, of course, many other methods for studying molecular stfucture, some of which are extremely powerful, although usually in limited areas. But, not all of chemistfy can be discussed here, so we will limit the topics to those mentioned.) Each of these methods measures something that is a little different, sometimes quite a bit different, from what the other methods measure. The calculational methods, described in the next chapter, generally calculate something that is still different from any of the above. The structures of the same molecule determined by these different methods are not, in general, identical. Hence, we need to understand how the structures obtained from each of these methods are interrelated. [Pg.7]

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