Uses of Electrospray

Although simple solutions can be examined by these electrospray techniques, often for a single substance dissolved in a solvent, straightforward evaporation of the solvent outside the mass spectrometer with separate insertion of the sample is sufficient. This situation is not true for all substances. Peptides, proteins, nucleotides, sugars, carbohydrates, mass organometallics, and many 

Lei the unknown mass be M and let the number ot unknown charges be n, corresponding to the addition ot n protons (n.H+)  

For two successive measured mass-to-charge ratios m and m two equations can be written, 

The best value for M will be obtained by averaging all the values individually calculated from all successive pairs. 

For mixture.s the picture is different. Unless the mixture is to be examined by MS/MS methods, usually it will be necessary to separate it into its individual components. This separation is most often done by gas or liquid chromatography. In the latter, small quantities of emerging mixture components dissolved in elution solvent would be laborious to deal with if each component had to be first isolated by evaporation of solvent before its introduction into the mass spectrometer. In such circumstances, the direct introduction, removal of solvent, and ionization provided by electrospray is a boon and puts LC/MS on a level with GC/MS for mixture analysis. Further, GC is normally concerned with volatile, relatively low-molecular-weight compounds and is of little or no use for the many polar, water soluble, high-molecular-mass substances such as the peptides, proteins, carbohydrates, nucleotides, and similar substances found in biological systems. LC/MS with an electrospray interface is frequently used in biochemical research and medical analysis. 

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These solutions are not always practicable and HPLC flow rates of up to 2 mlmin may be accommodated directly by the use of electrospray in conjunction with pneumatically assisted nebulization (the combination is also known as lonspray ) and/or a heated source inlet. The former is accomplished experimentally by using a probe that provides a flow of gas concentrically to the mobile phase stream, as shown in Figure 4.8, which aids the formation of droplets from the bulk liquid, and will allow a flow rate of around 200 p. min to be used. 

In contrast to ions generated by other ionization techniques, these ions do not occur at integer m jz values and this non-integer part of the mass is of crucial importance when making a precise determination of the molecular weight of the analyte involved - this being one of the major uses of electrospray ionization. 

In addition to the dissolved elements and compounds in the oceanic water column, a wide variety of water column chemicals are found in marine organisms and organic detritus. For example, a milliliter of surface seawater can contain on the order of 10 million viruses, 1 million bacteria, 100,000 phytoplankton, and 10,000 zooplankton [9]. With the advent of soft ionization processes for mass spectrometry systems, scientists have been able to study these marine organisms at molecular level. The use of electrospray ionization (ESI see Section 2.1.15), atmospheric pressure chemical ionization... 

N. J. Haskins, C. Eckers, A. J. Organ, M. F. Dunk and B. E. Winger, The use of electrospray ionization with Fourier transform ion cyclotron resonance mass spectrometry in the analysis of trace impurities in a drag substance. Rapid Communications in Mass Spectrometry, 1995,9(11), 1027-1030. 

Jackson, P. J., Brownsill, R. D., Taylor, A. R., and Walther, B. (1995). Use of electrospray ionization and neutral loss liquid chromatography/tandem mass spectrometry in drug metabolism studies. J. Mass Spectrom. 30 446-451. 

Berthon, L., Zorz, N., Lagrave, S., Gannaz, B., Hill, C. 2008. Use of electrospray ionization mass spectrometry (ESI-MS) for the characterization of complexes ligand-metallic cations in solution. ATALANTE 2008 Nuclear Fuel Cycles for a Sustainable Future, May, Montpellier, France. 

Lamouroux, C., Rateau, S., Mouhn, C. 2006. Use of electrospray ionization mass spectrometry for the study of Ln(III) complexation and extraction speciation with calixarene-CMPO in the fuel partitioning concept. Rapid Communications in Mass Spectrometry 20(13) 2041-2052. 

Sanwald P, David M, Dow J (1996) Use of electrospray ionization liquid chromatography-mass spectrometry to study the role of C YP2D6 in the in vitro metabolism of 5-hydroxytryptam-ine receptor antagonist. J Chromatogr B 678 53-61... 

The detection modes for a peptide map are the same as those described earlier for HPLC. Absorbance at low UV wavelengths is most often used. Absorbance at other wavelengths, tryptophan fluorescence, or fluorescence after derivatization might provide additional information on the location of a modification (see Section IV). The use of electrospray mass spectrometry on-line with HPLC is a powerful tool for peptide mapping that can identify the modification without further analysis.63... 

Mass spectrometry is one of the major techniques in the interdisciplinary field of proteomics. It provides a rapid, sensitive and reliable means of protein identification and structural determination, allowing for development in this newly baptised but yet classical field of biochemistry and biomedicine. The use of electrospray ionisation in conjunction with a tandem mass spectrometer (MS/MS) provides essential amino acid sequence information from the m/z values of the so-called b andy ions formed from cleavage of the amide bond of a protonated peptide. This reaction requires proton catalysis, and the mechanism is of interest in the present context, since it is closely related to the processes occurring in other protonated carboxylic acid derivatives. 

In recent years there has been a growing interest in the use of electrospray ionization-mass spectrometry (ESI-MS) either as a stand-alone technique, or following an analytical separation step like CE, to study and measure a wide variety of compounds in complex samples such us foods (Simo et al. 2005). ESI provides an effective means for ionising from large (e.g., proteins, peptides, carbohydrates) to small (e.g., amino acids, amines) analytes directly from solution prior to their MS analysis without a previous derivatization step. Santos et al. (2004) proposed the use of CE-ESI-MS for the separation and quantification of nine biogenic amines in white and red wines. More recently, the possibilities of two different CE-MS set-ups, namely, capillary electrophoresis-electrospray-ion trap mass spectrometry (CE-IT-MS) and capillary electrophoresis-electrospray-time of flight mass spectrometry (CE-TOE-MS) to analyze directly biogenic amines in wine samples without any previous treatment has been studied (Simo et al. 2008). 

Hayasaka, Y., Adams, K.S., Pocock, K.E, Baldock, G.A., Waters, E.J., Hoj, P.B. (2001). Use of electrospray mass spectrometry for mass determination of grape (Vitis vinifera) juice pathogenesis-related proteins A potential tool for varietal differentiation. J. Agric. Food Chem., 49, 1830-1839... 

T. Waters, X.-B. Wang and L.-S. Wang, Coord. Chem. Rev., 2007, 251, 474. Review describing the use of electrospray to transfer negatively charged transition metal complexes to the gas phase for photoelectron spectroscopy. Examples discussed include square planar and octahedral halide complexes, metal-metal bonded species, transition metal bis(diihiolene) complexes, and mononuclear and polynuclear iron-sulfur clusters. 

A specific P-globin adduct to Cys93 and Cysll2 was identified by the use of electrospray tandem mass spectrometry as well as by chemical transformation with the cysteine-selective reagent vinylpyridine and derivatization by S-carbamylation (Fidder et al, 2000). No method for quantification of this adduct was described. As of mid-2008, no specific adducts other than the above mentioned have been described in the literature. 

The evolution of the ESI source has been marked by the use of electrospray devices as interfaces between the separation systems such as HPLC or CE and MS detectors, the earliest instances of which were reported by Yamashita and Fenn [59] and Aleksandrov et al. [60] in the mid-1980s. Because ESI-MS is used in many areas of chemistry, a vast number of articles reporting specific modifications of the electrospray interface has been published so far. Also, instrument manufacturers have provided innovative solutions for more sensitive and reliable mass spectrometers. 

Although FAB has been used in polymer analysis, problems with fragmentation and the relatively low mass limit has made this less popular as new techniques have emerged. Plasma desorption has been used successfully but this too has waned in popularity with commercial spectrometers not really readily available. To a large extent polymer mass spectrometry equates to MALDI time-of-flight and the remainder of this article will bear this in mind. However, the use of electrospray ionisation (ESI) will be considered in conjunction with either quadrupole detectors or ion cyclotron resonance (ICR) N. B. ICR detectors can also be used with MALDI, as this is important and probably not as widely used as it could be. 

Exciting though the potential of electrospray ionization may seem, the use of electrosprays for liquid chromatography/mass spectrometry has been limited in practice by the severe restrictions on solvent composition and volumetric flow-rate that are amenable... 

Jackson, P.J. Brownsill, R.D. Taylor, A.R. Walther, B. Use of Electrospray Ionization and Neutral Loss Liquid Chromatography/Tandem Mass Spectrometry in Drug Metabolism Studies, J. Mass Spectrom. 30,446 51 (1995). 

Plumb, R.S. et al., Metabonomics The use of electrospray mass spectrometry coupled to reversed-phase liquid chromatography shows potential for the screening of rat urine in drug development, Rapid Commun. Mass Spectrom., 16(20), 1991, 2002. 

Giusti, M.M., Wrolstad, D.E., and Rodriguez-Saona, L.E. 2000. The use of electrospray and tandem mass spectrometry as a tool for the characterization of anthocyanin pigments. In Proceedings of the 4th International Symposium on Natural Colorants for Foods, Neutraceuticals, Beverages, Confectionery Cosmetics (J.F. Francis, ed.), pp. 95-109. SIC Publishing, Hamden. 

Of the 22 plenary and invited lectures presented in the Joe Chatt Chemistry session at Edinburgh, 18 are included in this volume, some in amended and expanded form. Three of these papers we believe to be sufficiently distinctive for it to be inappropriate for them to be assigned to one of the earlier sections. These concern the use of electrospray mass spectrometry to study the processes of eliminationfrom carbonyl clusters of ruthenium and iridium described by J. S. Mclndoe and coworkers, the synthesis and characterisation of complexes containing the Pt2S2 core also reporting the use of electrospray mass spectrometry) reported by T. S. A. Hor and colleagues and of squarate coordination complexes, described by F. Dumitru and colleagues. 

The covalent interactions of small molecules with DNA have also been studied using electrospray. The use of liquid chromatography in conjunction with electrospray has been reviewed. The use of electrospray in conjunction with capillary electrophoresis has also been investigated. The stabilities of duplexes formed from 3, 5 - and 2, 5 - linked DNA have been compared by electrospray The binding of metal ions to oligonucleotides has also been studied using electrospray ionisation,Fourier transform ion cyclotron mass spectrometry. ... 

Nuclear magnetic resonance spectroscopy provides the most conclusive evidence of both identity and purity [90] but few laboratories are equipped with such a resource and even fewer researchers with the experience to interpret the resulting data. Gas chromatography can be used to assess the chiral purity of derivatives, and mass spectrometry (MS) is a particularly sensitive and accurate measure of product purity. Use of electrospray ioni-... 

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