Mass spectrometry with nuclear magnetic resonance

Frequently, in work carried out to attempt to elucidate the microstructure of polymers and copolymers, it is found necessary to employ not one physical analytical technique, but a range of such techniques. The literature abounds in examples of this need. Judging by the number of papers published, three of the most useful and commonly used techniques are combinations of Fourier transform infrared spectroscopy (FTIR) or infrared (IR) spectroscopy and matrix assisted laser desorption-ionisation time-of-flight (MALDI-TOF) mass spectrometry with nuclear magnetic resonance spectroscopy or photon magnetic resonance spectroscopy. 

Tor reference. Positive identification can be made only by collecting the compound or transierring it as it elutes directly into another apparatus for analysis by other means, such as infrared or ultraviolet spectroscopy, mass spectrometry, or nuclear magnetic resonance. Commercially available apparatus is available which combines in a single unit both a gas chromatograph and an infrared, ultraviolet, or mass spectrometer for routine separation and identilicalion. The ancillary system may also be microprocessor-based, with an extensive memory for storing libraries of known infrared spectra or fragmentation patterns (in the case of mass spectrometers). Such systems allow microprocessor-controlled comparison and identilicalion of detected compounds. 

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. 

Stronger chemical evidence for the presence of a dithiolene in molybdopterin was obtained when the mild alkylation reagent iodoacetamide effectively trapped the dithiolene (65). This reaction yielded a derivative whose characterization by FAB mass spectrometry and nuclear magnetic resonance (NMR) was consistent with the structure shown in Fig. 5. The method appeared to leave the side chain intact and preserved the pterin oxidation state. From this experiment the view persisted that molybdopterin is a disubstituted dithiolene bearing a reduced pterin and a short chain terminated with a phosphate. 

As the glucose is metabolized, the metabolic derivatives become enriched with the isotopic carbon label and are detected using advanced technologies such as mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. Importantly, incorporation of isotopes into molecules can alter reaction mechanisms including the rate of a reaction-this is termed isotopic substitution and forms the basis of the kinetic isotope effect. 

Ramm, M. et al. Rapid analysis of nucleotide-activated sugars by high-performance liquid chromatography coupled with diode-array detection, electrospray ionization mass spectrometry and nuclear magnetic resonance. J. Chromatogr. A. 2004, 1034,139-148. 

The field of application for the isotope dilution method with radioactive tags, extends to measurements using stable isotope. Mass spectrometry or nuclear magnetic resonance are used to determine the variations in the isotopic concentrations. Chemical labelling using externally introduced tags consists of the addition to a sample of the same analyte but containing a stable isotope (e.g. H, C, N) as an internal standard. This method is as much used for molecular species as for atoms (around 60 have stable isotopes). 

Malinowski ER (1978) Theory of error for target factor analysis with applications to mass spectrometry and nuclear magnetic resonance spectrometry. Anal Chim Acta 103 359-354 Malinowski ER (1991) Factor Analysis in Chemistry. John Wiley, New York,... 

The ease of purification and remarkable stability of P. furiosus ferredoxin, together with the availability of the recombinant protein, has enabled it to become one of the best studied of all ferredoxins, with numerous investigations into the properties of both the protein and of its single [4Fe-4S] cluster. These include the use of spectroscopic techniques, such as electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), Mossbauer, mass spectrometry, and nuclear magnetic resonance (NMR). Such studies... 

Using mass spectrometry, proton nuclear magnetic resonance ( H NMR), COSY H NMR analysis, and calculation on the relative thermodynamic stability, Tan et al. (1998) identified a novel melatonin metabolite as cyclic 3-hydroxymelatonin. This is the product of reaction of melatonin with HO generated in two different cell-free in vitro systems. Cyclic 3-hydroxymelatonin also existed in urine of both human and rat. When rats were challenged with ionising radiation (800 cGy = LD50 for a one month period), as expected, urinary cyclic 3-hydroxymelatonin was doubled over that of the controls (P = 0.002). 

Secondary metabolites include a wide variety of compounds with different structures and chemical properties. Typically, isolation and estimation of secondary metabolites are carried out by extraction followed by quantification and separation using thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), gas chromatography (GC) and mass spectrometry (MS), nuclear magnetic resonance (NMR), or absorption spectroscopy. 

Flavor research technology has been rapidly changing with the development of very sensitive instmments capable of identifying ingredients, found in very small amounts, in very complex mixtures. Some of these instruments include gas-liquid chromatography, infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance. 

In another experiment, the resultant brown residue in the chromatography column (the top layer) was extracted with methanol to give about 0.01 grams of a tan solid. This material was analyzed using Mass Spectrometry and Nuclear Magnetic Resonance. 

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