Electrospray Ionization Mass Spectrometry ES-MS

Electrospray Ionization/Mass Spectrometry (ES/MS), a soft-ionization desorption technique using polar solvents such as water, methanol, or acetonitrile, was used for direct measurement of cations in solution. The first measurements carried out with mono or bis(crown-6) calix[4]arenes from an equimolar cation-extractant solution confirm that the calixarenes mono(crown-6) extract only one cesium cation. On the contrary, in the same conditions, bis(crown-6) calix[4]arenes can extract two cesium cations for a ratio Cs/BC6 equal to 2.5. The binuclear complex (composed of two cesium cations) is the major species. Cesium/sodium selectivity measurements implementing various mono or bis(crown-6) calix[4]arenes were in agreement with liquid/liquid results.42... 

After isolation and identification of the peptides containing these glycosylation sites, high pH anion exchange chromatography, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, and electrospray ionization mass spectrometry (ES-MS) were utilized to evaluate carbohydrate microheterogeneity. 

The ability of combinatorial chemistry to generate a myriad of compounds in a very short period of time sets demands upon the analytical techniques to produce a maximum of information in a minimum of time. A prime candidate for the analysis of combinatori-ally generated compounds is electrospray ionization-mass spectrometry (ES-MS) using a quadrupole mass analyzer. In the following section we wish to examine the practical aspects of ES-MS, and exemplify these on the routine analysis of several combinatorially generated compounds and libraries. Furthermore, attention will be paid to high-through-put and computer-assisted sample evaluation. 

The term nebulizer is used generally as a description for any spraying device, such as the hair spray mentioned above. It is normally applied to any means of forming an aerosol spray in which a volume of liquid is broken into a mist of vapor and small droplets and possibly even solid matter. There is a variety of nebulizer designs for transporting a solution of analyte in droplet form to a plasma torch in ICP/MS and to the inlet/ionization sources used in electrospray and mass spectrometry (ES/MS) and atmospheric-pressure chemical ionization and mass spectrometry (APCI/MS). 

Electrospray mass spectrometry (ES-MS) Nanoelectrospray ionization mass spectrometry (NanoESl-MS)... 

Mass spectrometry (MS) in its various forms, and with various procedures for vaporization and ionization, contributes to the identification and characterization of complex species by their isotopomer pattern of the intact ions (usually cation) and by their fragmentation pattern. Upon ionization by the rough electron impact (El) the molecular peak often does not appear, in contrast to the more gentle field desorption (FD) or fast-atom bombardment (FAB) techniques. An even more gentle way is provided by the electrospray (ES) method, which allows all ionic species (optionally cationic or anionic) present in solution to be detected. Descriptions of ESMS and its application to selected problems are published 45-47 also a representative application of this method in a study of phosphine-mercury complexes in solution is reported.48... 

HPLC-mass spectrometry (MS). MS conditions ionization mode, atmospheric pressure ionization-electrospray (API-ES) polarity, positive Vcap, 4000 V nebulizer pressure, 35 psig drying gas, 10 L min gas temperature, 350 °C fragmentor, 70 V scan range, 120-600 atm. 

The separation of intact polar lipids by liquid chromatography (LC) and the subsequent detection by mass spectrometry (MS) has today become straightforward. LC-MS is no longer a sophisticated technique only in the hands of specialists. Today, it is a routinely used, although advanced, analytical technique. The fields of application are expanding and today the use of LC-MS with electrospray (ES) ionization grows at the expense of other ionization techniques, at least where analysis of intact polar lipids is concerned. 

The content of this chapter focuses on the analysis of intact polar lipids by high-pressure liquid chromatography (HPLC) with flow or loop injection -and mass spectrometry (MS) or tandem mass spectrometry (MS-MS) using thermospray (TS), discharge-assisted TS [or plasmaspray (PSP)], electrospray (ES) and atmospheric pressure chemical ionization (APCI). It was intended to include only those papers describing the analysis of intact polar lipids by liquid chromatography on-line with MS. However, many papers describe flow or loop injection with MS and/or the analysis of derivatives of polar lipids. These papers, describing excellent applications of MS and/or MS-MS of polar lipids, are included since this chapter would not have been complete without them. 

Several mass spectrometric techniques including fast atom bombardment (FAB), plasma desorption (PD), matrix-assisted laser desorption/ionization (MALDI), and electrospray (ES) mass spectrometry (MS) are presently available for the analysis of peptides and proteins (Roepstorff and Richter, 1992). Of these techniques, mainly PDMS has gained footing in protein laboratories because the instrumentation is relatively cheap and simple to operate and because, taking advantage of a nitrocellulose matrix, it is compatible with most procedures in protein chemistry (Cotter, 1988 Roepstorff, 1989). Provided that the proper care is taken in the sample preparation procedure most peptides and small proteins (up to 10 kDa) are on a routine basis amenable to analysis by PDMS. Molecular mass information can be obtained with an accuracy of 0.1% or better. Structural information can be gained by application of successive biochemical or chemical procedures to the sample. 

With the advent of new methods by which gaseous ions can be formed from polar molecules and injected into an ion trap, a wider range of ion trap applications is possible. The coupling of liquid chromatography (LC) with electrospray (ES) ionization and with mass spectrometry (MS) in the early 1980s led to the development of new ion trap instruments... 

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