High mass resolution analysis

The position of the methyl group of 25b,c was deduced from high-resolution mass analysis as shown in Figs. 1 and 2. The mass fragmentation pattern of 25b was quite different from that of 25c, thus assuring the differ-... 

High resolution mass analysis of the ion at m/z 251 indicated that it has the empirical formula C h N202 > and is thus the 5,5-diphenyl-2,4-imidazolidinedione anion, resulting from cleavage of the C-N bond next to the imidazole ring. 

A high resolution mass analysis of the 220 peak reveals the presence of two compounds (220.1824 and 220.2190). The 220.1824 corresponds to the antioxidant, di-terf-butyl-p-cresol, which has a theoretical mass number of 220.1827. The 220.2190 peak corresponds to Ci6H28 which has a theoretical mass number of 220.2191. 

Basic characteristics of the quality of mass analyzer are resolving power (RP), which has been used to specify the ability of mass analyzers performing high-resolution mass analysis and it is defined and/or calculated by using the mass (M) and the full-width-at-half-maximum (FWHM) of a mass spectral peak, and mass accuracy (MA) is the measured error in m/q divided by the accurate m/q [105]. 

Fisher, I.P. and P. Fisher (1974), Analysis of high boiling petroleum streams by high resolution mass spectrometry . Talanta, Vol. 21, p. 867. 

The four-sector mass spectrometer is the ultimate in MS-MS instrumentation and consists of two high-resolution mass spectrometers in series. The strength of these instruments is in terms of their high-mass and high-resolution capabilities for both precursor-ion selection and product-ion analysis. Their cost, however, precludes their primary use for LC-MS and therefore they will not be considered any further here [12]. 

The following is a procedure recommended for elucidating the structure of complex organic molecules. It uses a combination of different NMR and other spectroscopic techniques. It assumes that the molecular formula has been deduced from elemental analysis or high-resolution mass spectrometry. Computer-based automated or interactive versions of similar approaches have also been devised for structural elucidation of complex natural products, such as SESAMI (systematic elucidation of structures by using artificial machine intelligence), but there is no substitute for the hard work, experience, and intuition of the chemist. 

The nature of water residue analysis has changed dramatically over the past 60 years. Advances in SPE media have made the isolation of hard to extract residues more attainable. The use of specific and sensitive instrumentation as in HPLC/MS/MS has even precluded the need for extraction in many cases, since the samples can be directly analyzed as they are received from the Held. The future holds even more improvements in sensitivity with rugged new API interfaces and high-resolution mass spectrometers that will dramatically increase the specificity of detection and ease of analysis. 

Polymer/additive analysis greatly benefits from high-resolution mass data, which often leads to unambiguous identification of (known) additives. However, the investment and operating costs of this instrument do not easily justify its (exclusive) use for the purpose of routine polymer/additive analysis. Analysis of organic polymer additives by means of mass spectrometry is aided by the utilisation of precursor ion and second-generation product ion (MS3) scanning experiments [169], A four-sector... 

Further evidence consistent with the polar radical pair mechanism was provided by a crossover experiment (Scheme 6.26). A 1 1 mixture of labeled 8Z /8 and unlabeled 8Z/8E was heated in xylene at 125 °C for 2h and at 135 °C for 4h to afford hydroxypyrimidinones 3 and 3. Analysis of the products by high resolution mass spectrometry showed no crossover between the labeled and unlabeled fragments. This result reinforces the computational results discussed previously wherein PRP recombines to give product within the solvent cage (Scheme 6.24). 

In comparison to humantenine (15), the structure of which has been confirmed by X-ray diffraction analysis, structure 16 can be assigned to humantenirine with reasonable confidence. The proposed structure is supported by the fragmentation pattern (high-resolution mass spectroscopy and... 

Field et al. [747] used ICP high-resolution mass spectrometry to determine vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium, and lead in seawater. Each analysis required 50 p,l sample and a 6 minute analysis time. 

High resolution mass spectrometry becomes indispensable for the analysis of biomolecules with ESI (see Chapter 2, Section 2.1.15) and MALDI (see Section 2.1.22) techniques. In these cases very high resolving power and accuracy of measurements are required to measure reliably the real masses of the sample molecules. 

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