Mass spectrometry direct infusion

McDougall G, Martinussen I and Stewart D. 2008. Towards fruitful metabolomics high throughput analyses of polyphenol composition in berries using direct infusion mass spectrometry. J Chromatogr B 871(2) 362-369. 

Direct infusion mass spectrometry is a popular technique used by medicinal chemists to check the molecular mass of target compounds. In... 

Different analytical chemistry methods are used for analysis of the metabolome (Figure 3). Direct-infusion mass spectrometry (DI-MS) on both, low and (ultra)high resolution MS, infuses raw metabolite extracts in the mass spectrometer without prior chromatography or electrophoretic separation and often uses high-resolution mass spectrometers. This method offers fast analysis with low duty cycles however, isomeric and isobaric substances cannot be... 

Evidence for the presence of covalent adducts involving proanthocyanidins and anthocyanidins was also observed by infusion mass spectrometry. These minor ions appeared in two series, one series starting at m/z 781 and one at m/z 783. Each of these series is observable up to m/z 2509/2511, with ions separated by a mass of 288 (Figure 4). Based upon previous studies and speculation, these ions were consistent with two types of anthocyanin-proanthocyanidin adducts. Specifically, these ions agree with the direct condensation products of... 

Castrillo, J. L. Hayes, A. Mohammed, S. Gaskell, S. J. Oliver, S. G. An optimized protocol for metabolome analysis in yeast using direct infusion electrospray mass spectrometry. Phytochemistry 2003, 62, 929-937. 

Lewis DA, Guzzetta AW, Hancock WS, Costello M. 1994. Characterization of humanized anti-TAC, an antibody directed against the interleukin 2 receptor, using electrospray ionization mass spectrometry by direct infusion, LC/MS, and MS/MS. Anal Chem 66 585. 

Mass spectrometry enables the type of direct analyses described, but it does have its limitations. Online operation forces detection at infusion concentrations, in salty buffer and under complex mixture conditions. General ion suppression results from the buffer and mixture components, and mixture complexity can tax the resolution of even the best mass spectrometers. Increasing compound concentration is not the answer, as this leads to problems of solubility and increased compound consumption. We have found that the online method can work successfully for up to 100 compounds per analysis, but the false negative rate becomes appreciable [21]. As an alternative for ligand discovery purposes, we have developed a FAC-LC/MS system in which FAC effluent is sampled and analyzed by LC/MS [19]. This system offers the ability to concentrate mixture components and introduces another dimension to the data in order to tolerate more complex mixtures (Fig. 6.9). Using this system, we have screened approximately 1000 modified trisaccharide acceptor analogs targeting immobilized N-... 

Figure 14.5 Modified-ESI source for the direct infusion of undiluted ILs. A stainless steel wire is placed in the spray, leading to the optimal vaporization of the IL. Additionally, an orthogonal ESI source is used. Only a part of the IL ions is transferred into the MS, thus minimizing pollution of the source. (Modified from Dyson, R J. et al.. Direct probe electrospray (and nanospray) ionization mass spectrometry of neat ionic liquids. Chem. Commun., 2204, 2004. Reproduced by permission of the Royal Society of Chemistry.)...

Erve, J. C. L., DeMaio, W., and Talaat, R. E. (2008). Rapid metabolite identification with sub parts-per million mass accuracy from biological matrices by direct infusion nanoelectrospray ionization after clean-up on a ZipTip and LTQ/Orbitrap mass spectrometry. Rapid... 

Dethy, J. M., Ackermann, B. L., Delatour, C., Henion, J. D., and Schultz, G. A. (2003a). Demonstration of direct bioanalysis of drugs in plasma using nanoelectrospray infusion from a silicon chip coupled with tandem mass spectrometry. Anal. Chem. 75 805-811. 

In lipidomics, MS can be used either by direct infusion, that is, by the so-called shotgun MS, or in combination with chromatographic separation, typically LC and sometimes also with GC. Both approaches have their own advantages and limitations. Most targeted lipid analyses are performed with liquid chromatography coupled to mass spectrometry (LC-MS), while the use of gas chromatography-mass spectrometry (GC-MS) is utilized only for the analysis of fatty acids and some steroids. In addition, surface analysis by MS has been applied in lipid analysis of intact tissues. 

The infusion into the field of innovative approaches is revolutionizing our understanding of this process in the world s oceans. Sensitive new direct tracer methods of quantifying N2 fixation and improvements in mass spectrometry in parallel... 

In ESI mass spectrometry ° ° ° the sample, dissolved in an appropriate solvent (usually a 50 50 mixture of methanol and water for proteins), is infused directly into the ionization chamber of the spectrometer through a fused silica capillary. At the end of the capillary the solution is subjected to electrical stress created... 

Table 3.10 Fragmentation of M+ ions of anthocyanins present in the Clinton extract (chromatogram Figure 3.15) by direct infusion ESI multiple step mass spectrometry (MSn). (Reprinted from American Journal of Enology and Viticulture 51, Favretto and Flamini, Copyright 2000).

Dethy, J.M. Ackermann, B.L. Delatour, C. Henion, J.D. Schultz, G.A. "Demonstration of Direct Bioanalysis of Drugs in Plasma Using Nanoelectrospray Infusion from a Silicon Chip Coupled with Tandem Mass Spectrometry, Anal. Chem. 75, 805-811 (2003). 

Zahn, J.A. Higgs, R.E. Hilton, M.D. Use of Direct-Infusion Electrospray Mass Spectrometry To Guide Empirical Development of Improved Conditions for Expression of Secondary Metabolites from Actinomycetes, Appl. Environ. Microbiol. 67, 377-386 (2001). 

Figure 6.7. Product ion spectrum of direct infusion ESI generated [M-H]- species of piceatannol. The ESI conditions are the same reported in the caption of Fig. 6.6. (Reprinted from Rapid Communications in Mass Spectrometry 22, Stella et al., Collisionally induced fragmentation of [M-Hp species of resveratrol and piceatannol investigated by deuterium labeling and accurate mass measurements, p. 3870, Copyright 2008, with permission from John Wiley Sons, Ltd.)...

Electrospray ionization and MALDI represent major advances in the application of mass spectrometry to analysis of biomolecules. Although in many cases the two techniques are able to provide the same information, quite frequently they are complementary. For a variety of reasons, some samples are more successfully analyzed by MALDI and other by ESI. Thus, it is highly beneficial to have access to both types of instrument for characterization of synthetic peptides. In ESI-MS, the samples are introduced in solution at flow rates from less than 1 tL/min up to 1 mL/min, depending on the design of the ESI interface. Pure samples and simple mixtures are often analyzed by direct infusion more complex mixtures (such as proteolytic digests) generally require either on-line or off-line HPLC fractionation prior to MS analysis. 

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