Solvent resonance-mass spectrometry

Owing to its stability, solubility, and highly reproducible oxidation behavior, ferrocene has long been used as an electrochemical standard in nonaqueous solvents. Not surprisingly, the electron-donor or -acceptor properties of ring substituents in ferrocenes and other metallocenes have been repeatedly evaluated with electrochemical techniques. Measurements have been obtained using polarography,150 cyclic voltammetry (CV),151 chronopotentiometry,152 photoelectron spectroscopy, 53 and Fourier transform ion cyclotron resonance mass spectrometry.154 Extensive compilations of such data are available.155 156 Historically, variations of oxidation potentials have been discussed almost solely in terms of the... 

If the objective is identification (qualitative analysis), it suffices to compare the spectrum of the analyte with that of a standard, both recorded in the same solvent and at an identical pH. This is not the main application of UV-Vis spectrophotometry as the best results in this context are provided by spectroscopic methods considered more effective for the study of the molecular structure of organic compounds (infrared, nuclear magnetic resonance, mass spectrometry, and X-ray diffraction). However, UV-Vis spectrophotometry is a source of relevant supplementary information that helps in the elucidation of molecular structures of drugs, impurities, metabolites, intermediate compounds of degradation, etc. 

Klein, G.C. Kim, S. Rodgers, R.P. Marshall, A.G. Yen, A Asomaning, S. (2006). Mass Spectral Analysis of Asphaltenes. I. Compwsitional Differences between Pressure-Drop and Solvent-Drop Asphaltenes Determined by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Energy Fuels, Vol.20, No.5, pp. 1965-1972... 

Starting from 27, cyclo-Cig was prepared in the gas phase by laser flash heating and the neutral product, formed by stepwise elimination of three anthracene molecules in retro-Diels-Alder reactions, was detected by resonant two-photon-ionization time-of-flight mass spectrometry [23]. However, all attempts to prepare macroscopic quantities of the cyclocarbon by flash vacuum pyrolysis using solvent-assisted sublimation [50] only afforded anthracene and polymeric material. 

Several modem analytical instruments are powerful tools for the characterisation of end groups. Molecular spectroscopic techniques are commonly employed for this purpose. Nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and mass spectrometry (MS), often in combination, can be used to elucidate the end group structures for many polymer systems more traditional chemical methods, such as titration, are still in wide use, but employed more for specific applications, for example, determining acid end group levels. Nowadays, NMR spectroscopy is usually the first technique employed, providing the polymer system is soluble in organic solvents, as quantification of the levels of... 

Halcinonide dissolved in either methanol, deutero-methanol, aqueous ammonia-methanol, or deuterium oxide deuter-ated ammonia-methanol solvents appears stable after storage for six days at 50°, using nuclear magnetic resonance and mass spectrometry.70... 

Several other analytical procedures exist in which solvent extraction may be applied. Thus extraction has been used in a limited number of analyses with procedures such as (1) luminescence (fluorimetry), where, for example, the detection limit of rhodamine complexes of gallium or indium can be increased by extraction [28] (2) electron spin resonance using a spin-labelled extractant [29] and (3) mass spectrometry, where an organic extract of the analyte is evaporated onto pure AI2O3 before analysis [30]. 

Preparative HPLC is another convenient method for isolating degradants from excipient compatibility matrices (72,73). The peaks from stressed samples can be collected, the solvent removed with a rotary evaporator, and the remaining solution lyophilized to obtain purified compounds. The samples can then be analyzed by other methods such as mass spectrometry and nuclear magnetic resonance (NMR) in order to identify the molecular composition. 

Silylium ions R3Si+ are known to be more stable in the gas phase than their carbon analogues, which is due to the fact that silicon is more electropositive than carbon. It is easy to observe them by mass spectrometry or ion cyclotron resonance spectroscopy of triorganosilyl compounds. [5] However, their existence in solvent phases is difficult to prove and, therefore, is still a matter of dispute. Early attempts to synthesize silylium ions in solution with methods successful in the preparation of carbocations were not successful. [78] The lack of stability of R3Si+ in solution was attributed to the strong tendency of Si to form hypercoordinated compounds, in which Si has five or even six bonding partners. [79]... 

Different techniques have been used to study the products of photoreactions of organometallic compounds for example, irradiation of the arene complexes [CpFe() -arene)]+ resulted in the substitution of the arene by solvent or other potential ligands present in solution. In solutions containing an epoxide monomer, this photochemical reaction generated a species that initiated polymerization. Ion cyclotron resonance Fourier transform mass spectrometry and electrospray ionization mass spectrometry were used to elucidate the mechanism of these photoinitiated polymerizations. 

The exact chemical composition of a plant extract is not always completely known. Many articles published in recent years attempt to identify the compounds structure by coupling chromatography with spectro-metric methods. Modern densitometers are able to record the in situ ultraviolet-visible (UV-vis) spectra of a separated substance on a TLC plate [6]. Thin-layer chromatography can be also coupled with other methods in order to enhance the identification of compounds, such as mass spectrometry (MS) or nuclear magnetic resonance (NMR). There are devices able to record the in situ spectra on the TLC plate, or the separated substance is removed from the plate together with the layer, then extracted in a small volume of an adequate solvent, and the sample can be used for obtaining the spectra [6,7]. 

The analysis of CAD and alkamides has been completed using a variety of analytical techniques that include high-performance liquid chromatography (HPLC), capillary electrophoresis, gas chromatography (GC), GC-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), and nuclear magnetic resonance (NMR). Sample preparation methodologies utilize hexane, methanol and ethanol as the primary extraction solvents. 

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