Mass spectrometry molecular weights using

Various techniques have been used depending on the polymer and the nature of the chemical transformations infrared, ultraviolet and electron spin resonance spectroscopy, vapour phase chromatography, mass spectrometry, molecular weight and gel fraction determination, luminescence measurements, etc. These techniques have recently been discussed in a well-documented review on analytical methods applied to the study of the photodegradation of polymers [19]. 

Mass Spectrometry. Field desorption mass spectrometry has been used to analy2e PPO (179). Average molecular weight parameters (M and could be determined using either protonated (MH + ) or cation attachment (MNa + ) ions. Good agreement was found between fdms and data supphed by the manufacturer, usually less than 5% difference in all cases up to about 3000 amu. Laser desorption Fourier transform mass spectrometry was used to measure PPG ion and it was claimed that ions up to m/2 9700 (PEG) can be analy2ed by this method (180). 

Mass Spectrometry (MS) Approaches Used in the Determination of Molecular Weights of Oligomeric and Polymeric Materials... 

Polymers are not easily converted to gas-phase ions but this is a requirement for compounds analyzed by mass spectrometry. Despite this difficulty, mass spectrometry has been utilized to study various aspects of polymers polymers can be characterized - among others - with respect to their chemical composition, to their end groups, and to their molecular weight. Moreover, mass spectrometry can be used to study polymer surfaces. 

Mass spectrometry should be used discriminately where a maximum amount of information can be expected. The heavier nonvolatile feedstocks are for practical purposes, beyond the useful range of routine mass spectrometry. At the elevated temperatures necessary to encourage volatility, thermal decomposition will occur in the inlet and any subsequent analysis would be biased to the low molecular weight end and to the lower molecular products produced by the thermal decomposition. 

Structure determination for new GAs. Mass spectrometry is a useful tool for identifying GAs whose structures have been previously determined, in which case comparison of mass spectra is sufficient. In contrast, the characterization of GAs of unknown structure is a much more difficult and time-consuming task. In these cases mass spectrometry can give information such as molecular weight and some indications of structure. 

Mass spectrometry has been used to determine the molecular weight of small labile molecules precisely. The analysis of macromolecules became possible following the development of novel mass spectrometry technologies, especially, Matrix-assisted laser desorption ionization time of flight mass... 

The major side reactions in lactide ROP are intramolecular and intermolecular transesterification (Fig. 3). Intramolecular transesterification leads to formation of mixtures of linear and cyclic polymers, ultimately reducing the molecular weight of the polymer sample. Intermolecular transesterification, or chain transfer, leads to a broadening of the polymer molecular weight distribution. The extent of these processes can be experimentally verified using mass spectrometry, most commonly using ESI or MALDI-ToF mass spectrometry and by l3C hi) NMR spectroscopy [24, 25]. 

Chemical ionization mass spectrometry is not useful for peak matching (either manually or by computer) nor is it particularly useful for structure elucidation its main use is for the detection of molecular ions and hence molecular weights. 

Although mass spectrometry has many uses in research, we are interested in it for only a limited amount of data. The most important piece of information it provides for us is the molecular weight of an unknown. A mass spectrum can also show if an unknown is branched... 

Mass spectrometry is widely used in organometallic and cluster chemistry as a rapid means of determining the molecular weight, the number of carbonyl and other ligands present, and even the number of metal atoms present. In the case of relatively small molecules it is also possible to detect hydrogen loss. 

Mass spectrometry would be useful even if molecular weight and formula were the only information that could be obtained. In fact, though, we can get much more. For example, the mass spectrum of a compound serves as... 

Mass spectrometry is widely used for the qualitative analysis of unknowns samples, and in particular, for the identification and characterization of biological macromolecules. Recent decades have seen the introduction and optimization of the so-called soft ionization methods that provide intact, vapor-phase biomolecular ions for separation and detection. This chapter considers MS fundamentals, ionization methods, and applications to biological macromolecules. Conventional mass spectrometers used for low volatile molecular weight samples that are introduced in the vapor phase are called single-focusing mass spectrometers, and use an electron-impact ion source.1 Figure 15.1 shows a diagram of this type of instrument. 

Mass spectrometry is generally useful only to obtain information on the molecular weight and to identify the type and functional groups bound to the terpenoid core. Soft ionization techniques must be employed (FAB, DC1, TSP). The spectra of Winterstein esters are characterized by a prominent peak at m z 210, and those of the X,W-dimethylphenylisoserine esters at 226, corresponding to the aminoacidic side chain [58],... 

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