Mass spec

Vartanian V H, Anderson J S and Laude D A 1995 Advances in trapped ion cells for Fourier transform ion cyclotron resonance mass spectrometry Mass Spec. Rev. 41 1-19... 

Although GGMS is the most widely used ana lytical method that combines a chromatographic sep aration with the identification power of mass spectrometry it is not the only one Chemists have coupled mass spectrometers to most of the mstru ments that are used to separate mixtures Perhaps the ultimate is mass spectrometry/mass spectrome try (MS/MS) m which one mass spectrometer gener ates and separates the molecular ions of the components of a mixture and a second mass spec trometer examines their fragmentation patterns ... 

Understanding how molecules fragment upon electron impact permits a mass spec trum to be analyzed m sufficient detail to deduce the structure of an unknown compound Thousands of compounds of known structure have been examined by mass spectrome try and the fragmentation patterns that characterize different classes are well docu mented As various groups are covered m subsequent chapters aspects of their fragmentation behavior under conditions of electron impact will be descnbed... 

Mass Spectrometry The molecular ion peak is usually quite small m the mass spec trum of an alcohol A peak corresponding to loss of water is often evident Alcohols also fragment readily by a pathway m which the molecular ion loses an alkyl group from the... 

An alternative approach to peptide sequencing uses a dry method in which the whole sequence is obtained from a mass spectrum, thereby obviating the need for multiple reactions. Mass spec-trometrically, a chain of amino acids breaks down predominantly through cleavage of the amide bonds, similar to the result of chemical hydrolysis. From the mass spectrum, identification of the molecular ion, which gives the total molecular mass, followed by examination of the spectrum for characteristic fragment ions representing successive amino acid residues allows the sequence to be read off in the most favorable cases. 

Mounting electrodes in a bioreactor is costly, and there is an additional contamination risk for sensitive cell cultures. Some other sensors of prac ticai importance are those for dissolved oxygen and for dissolved carbon dioxide. The analysis of gas exiting from a bioreactor with an infrared unit that detects carbon dioxide or a paramagnetic unit that detects oxygen (after carbon dioxide removal) has been replaced by mass spec trophotometry. Gas chromatographic procedures coupled with a mass spectrophotometer will detect 1 the volatile components. 

Fig. 3.3. Experimental arrangement used by Krauss and Gruen for SSIMS [3.8] a qua-drupole mass spectrometer was used for mass analysis and a retarding-field analyzer for prior energy selection (a) ion gun (b)-(d) lenses 1-3 (e) quadrupole mass spec-...

M. Heiraiz, G. Reglero, T. Heiraiz and E. Loyola, Analysis of wine distillates made from muscat grapes (Pisco) by multidimensional gas cliromatography and mass spec-ti ometry , J. Agric. Food Chem. 38 1540-1543 (1990). 

The unmodified form of coelenterazine, C26H2i03N3(mass spec. M+ 423), can be crystallized from methanol as orange-yellow prisms with a melting point of 175-178°C (dec). In methanol, coelenterazine is fluorescent in yellow, and its ultraviolet absorption spectrum shows a maximum at 435 nm (s 9,800), as shown in Fig. 5.1. 

Analysis. 1-MNN is best identified by redn to the amine with Sn and 10% HC1, which is converted to the benzenesulfonamide, mp 167° or the benzamide, mp 160° (Ref 36). The picrate, CA Registry No 29754-26-5, is also known (Ref 37). It has been found in cn de TNT recovered from Comp B (probably anCng from the presence of naphthalene in coml toluene), from which it was isolated by gas chromatography and identified by mass spec (Ref 40). Standard anal procedures for Mil grade 1-MNN are given in Ref 35 Flash Point. Closed Cup, 327°F (Ref 42)... 

More recent prepns are by the reaction of tetra-fluorohydrazine (F2NNF2) with thio phenol, yield up to 74% (Ref 7) by treatment of tri-phenylmethyldifluoramine with sulfuric acid, yield almost quant, purity by mass spec 99%... 

The only author to postulate a homolytic mechanism in the last few decades was Deng (1989). His arguments are based on the formation of small amounts of fluorinated bi- and polyphenyls in thermal fluoro-de-diazoniations and in mass-spec-trometric degradations of benzenediazonium tetrafluoroborate and its substituted derivatives. However, he does not include a critical discussion of his work. 

L.J.F., and Liskamp, R.M.J. Comparing mass spectrometric characteristics of peptides and peptoids — 2. J. Mass Spec. 

MejSiCHzCu 1(70) M.p. 78°-79° (decomp.) w tetrameric in C6H6 hexameric in cyclohexane (Me3SiCH2Cu) + in mass spec. 176a... 

Mercadante A.Z., Rodriguez-Amaya, D.B., and Britton, G., HPLC and mass spec-trometric analysis of carotenoids from mango, J. Agric. Food Chem., 45, 120, 1997. 

Modern reviews of BDEs in closed-shell molecules measured by using mass spec-trometric methods have been provided by Ellison and co-workers. ° Additional evaluations have been provided by Ervin and DeTuri. A list of important fundamental hydrocarbon BDEs is given in Table 5.2. 

Embrechts, J. Lemiere, F. Dongen, W. V. Esmans, E. L. Buytaert, P. van Marck, E. Kockx, M. Makar, A. Detection of estrogen DNA-adducts in human breast tumor tissue and healthy tissue by combined nano LC-nano ES tandem mass spectrometry. J. Am. Soc. Mass Spec from. 2003, 14, 482M-91. 

Al-Saad, K. A. Zabrouskov, V. Siems, W. F. Knowles, N. R. Hannan, R. M. Hill, H. H. Matrix assisted laser desorption/ionization time-of-flight mass spectrometry of lipids ionization and prompt fragmentation patterns. Rapid Comm. Mass Spec-trom. 2003,17, 87-96. 

---