Electrospray ionization-MS

Ivanov, A.R., Zang, L., Karger, B. L. (2003). Low-attomole electrospray ionization MS and MS/ MS analysis of protein tryptic digests using 20 pm-i.d. polystyrene-divinylbenzene monolithic capillary columns. Anal. Chem. 75, 5306-5316. 

CID collision-induced dissociation ESI electrospray ionization MS mass spectrometry... 

The mechanism of zinc deprivation by 3-nitrosobenzamide was elucidated most recently. When the reconstituted nucleocapsid protein p7 of HIV-1 (15 i-M) was incubated with 3-nitrosobenzamide (300 iM) at pH 7.5, three disulfide bonds per protein molecule were formed while 3-nitrosobenzamide was reduced to the hydroxylamine. Molecular masses of p7 adducts augmented by one or two 3-nitrosobenzamide residues were observed by electrospray ionization MS, consistent with covalent bond formation between cysteine sulfur and the nitroso nitrogen atom127. 

LC-NMR can be used to identify natural products in crnde plant extracts that usually consist of complex mixtnres. The crnde natural product extracts normally contain a great nnmber of closely related and difficult-to-separate compounds. The classical separation approach may become very tedious and time-consuming. The directly conpled HPLC-NMR presents an efficient separation techniqne together with a powerfnl spectroscopic method to speed up the identification process. LC-NMR has been nsed extensively for characterization of natnral prodncts. More recently, the combination of LC-NMR and LC-MS has been further developed in this field. Eor example, Wilson et al. have nsed combined on-flow NMR and electrospray ionization MS to characterize ecdysteroids in extracts of silene otites. After reversed-phase HPLC nsing D2O in acetonitrile-dj and UV detection, the LC flow was split 95 5 for the simnl-taneous detection by NMR and MS. The peaks of interest were analyzed by stop-flow NMR to give better quality spectra for structural assignment. 

Chen, Y. R., Tseng, M. C., Chang, Y. Z., and Her, G. R. (2003). A low-flow CE/electrospray ionization MS interface for capillary zone electrophoresis, large-volume sample stacking, and micellar electroklnetlc chromatography. Anal. Chem. 75, 503 — 508. 

Determination of Perchlorate in Drinking Water by LC Electrospray Ionization MS... 

Part IV covers the relevance of new combination (i.e., hyphenation) techniques such as CE-ESI- (electrospray ionization) MS (mass spectrometry) and CE-ESI-TOF- (time of flight) MS for ACE. 

There are three major ionization sources now used for steroid LC-MS electrospray ionization MS (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI). Under optimal conditions, all ionization methods have similar absolute sensitivities. ESI is preferred for polar and charged (steroid conjugates) molecules, but derivatization or chemical modification of less-polar molecules may be necessary for this technique to match the sensitivity of APPI or APCI. 

Figure F2.4.1 Liquid chromatography/mass spectrometry (LC/MS) analysis of isomeric carotenes in a hexane extract from 0.5 ml human serum. Positive ion electrospray ionization MS was used on a quadrupole mass spectrometer with selected ion monitoring to record the molecular ions of lycopene, p-carotene, and a-carotene at m/z (mass-to-charge ratio) 536. A C30 HPLC column was used for separation with a gradient from methanol to methyl-ferf-butyl ether. The a -trans isomer of lycopene was detected at a retention time of 38.1 min and various c/ s isomers of lycopene eluted between 27 and 39 min. The all-frans isomers of a-carotene and P-carotene were detected at 17.3 and 19.3 min, respectively.

Plastic microdevices for high-throughput screening with MS detection were also prepared for detection of aflatoxins and barbiturates. These devices incorporated concentration techniques interfaced with electrospray ionization MS (ESI-MS) through capillaries [2], The microfluidic device for aflatoxin detection employed an affinity dialysis technique, in which a poly (vinylidene fluoride) (PVDF) membrane was incorporated in the microchip between two channels. Small molecules were dialyzed from the aflatoxin/antibody complexes, which were then analyzed by MS. A similar device was used for concentrating barbiturate/antibody complexes using an affinity ultrafiltration technique. A barbiturate solution was mixed with antibodies and then flowed into the device, where uncomplexed barbiturates were removed by filtration. The antibody complex was then dissociated and electrokinetically mobilized for MS analysis. In each case, the affinity preconcentration improved the sensitivity by at least one to two orders of magnitude over previously reported detection limits. 

PLE pressurized liquid extraction, LLE liquid-liquid extraction, MAA methacrylic acid, EGDMA ethylene glycol dimethacrylate, HPLC high-performance liquid chromatography, LC hquid chromatography, ESI electrospray ionization, MS mass spectrometry... 

Elaboration of nerve agent toxicokinetics requires sophisticated analytical tools to detect and, if possible, to quantify the free toxicants as well as adducts with proteins and enzymes. Analysis of OP nerve agents has been performed by capillary electrophoresis (CE), biosensors, matrix-assisted laser desorption/ionization (MALDI) MS, desorption electrospray ionization MS (DESI MS), ion mobility time-of-flight MS (IM-TOF MS), nuclear magnetic resonance spectroscopy (NMR), LC-UV, gas chromatography (GC), and many more techniques (Hooijschuur et al, 2002 John et al, 2008). 

Various HPLC-MS methods were examined to establish the optimal ion source and detector operating conditions for the detection or determination of low molecular mass phenols and flavan-3-ols. Atmospheric pressnre electrospray ionization MS (ESI-MS) in... 

Heeft, E.v.d. Hove, G.J.t. Herberts, C.A. Meiring, H.D. Els, C.A.C.M.v. Jong, A.P.J.M.d. A Microcapillary Column Switching HPLC-Electrospray Ionization MS System for the Direct Identification of Peptides Presented by Major Histocompatibility Complex Class I Molecules, Anal. Chem. 70, 3742-3751 (1998). 

Mass spectroscopy (MS) and isothermal calorimetry (ITC) also have been utilized as screening tools. MS techniques, such as non-denaturing electrospray ionization MS (ESI-MS), use mass identification as the means for the detection of reversible binding events. MS analysis allows for simultaneous binding of multiple fragments, and hence direct stoichiometric detection of the binding events. Despite such advantages, application is at times limited because the protein of interest may... 

HA, heterocyclic amine AA, aromatic amine PA, polyamine Al, aliphatic amine N, nitrosamine BCD, electrochemical UV, ultraviolet FL, fluorescence TSI, thermospray ionization ESI, electrospray ionization MS, MS-tandem mass spectrometry SIM, selected ion monitoring A, air H, water W, waste. 

Electrospray ionization MS -MS ethyUiexylbenzoate Tobacco-specific nitrosamines 94... 

Idborg-Bjorkman, H., P-O. Edlund, O. M. Kvalein, I. Schuppe-Koistinen, and S. P. Jacobsen. 2003. Screening of biomarkers in rat urine using LC/mass electrospray ionization-MS and two-way data analysis. Analytical Chemistry 75 4784 792. 

The C-H activation reactions of complexes Cp (PMe3)lr(CH3) and Cp(PMe3)Ir(CH3)" has been studied by a combination of electrospray ionization MS/MS techniques, isotopic labeling experiments in the gas phase and in... 

Although substantial progress has been made in determining acrylamide, a recent interlaboratory comparison showed that many current methods are not satisfactory for samples in complex matrices. liven with relatively simple samples, the range of results was loo wide to be acceptable. Hius. more improvements in analytical methodology are certainty in order. A fully validated improved LC/MS/ MS method was recently reported that uses isotope dilution. l.C. and electrospray ionization MS/MS. lixcellem results were obtained on chocolate powders, cocoa, and coffec. 

Matrix-assisted laser desorption ionisation/time of flight (i.e., MALD-TOF) MS Electrospray ionization MS SSCP - Quantitative single-strand conformation polymorphism analysis... 

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