Electrospray Ionisation Mass Spectrometry ESI-MS

Electrosprays are generated by dispersing a liquid into small droplets via an electric field. This method has been known for a long time and is used for a variety of tasks 

ESI enables the production of molecular ions directly from samples in solution. It can be used for small as well as large biopolymers up to about 200,000 Da including peptides, proteins, carbohydrates, DNA fragments and lipids. Unlike MALDI, ESI is a continuous ionisation method and suitable for coupling with liquid separation methods like HPLC (chapter 2) or CE (chapter 3.3). 

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In common with M. macedonicus, urine from male M. spretus also demonstrated a MUP-sized band following gel electrophoresis. The proteins within this band were analysed by high resolution anion exchange chromatography and electrospray ionisation mass spectrometry (ESI-MS). The former technique produced an elution profile consisting of just three peaks, in contrast to both the more complex patterns observed previously from M. m. domesticus and the single major peak in M. macedonicus. Furthermore, similar analyses from five individual males resulted in near... 

To shed light on the mechanism of formation of silsesquioxane a7b3, to identify the species formed during the process, and to try to explain the high selectivity towards structure a7b3 of the optimised synthetic method described above (64% yield in 18 h), the synthesis of cyclopentyl silsesquioxane a7b3 was monitored by electrospray ionisation mass spectrometry (ESI MS) [50-52] and in situ attenuated total reflection Fourier-transform infrared (ATR FTIR) spectroscopy [53, 54]. Spectroscopic data from the latter were analysed using chemometric methods to identify the pure component spectra and relative concentration profiles. 

We have developed a method for analysis of genetic alterations in PCR amplified DNA fragments using electrospray ionisation mass spectrometry (ESI-MS) termed Short Oligonucleotide Mass Analysis (SOMA). The technique is highly accurate and has been applied to genotyping individuals and to mutational analysis of human tumours. 

D. Ekeberg, S.H. Knutsen, and M. Sletmoen, Negative-ion electrospray ionisation-mass spectrometry (ESI-MS) as a tool for analysing structural heterogeneity in kappa-carrageenan oligosaccharides, Carbohydr. Res., 334 (1), 49-59,2001. 

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). 

Owing to the anionic character of LAS, an electrospray ionisation (ESI) interface operated in negative ion mode is particularly attractive for the mass spectrometric detection of this surfactant type. Consequently, a great part of the atmospheric pressure ionisation-mass spectrometry (API-MS) work on LAS is devoted to the application of (— )-ESI-MS. 

For quantitative analysis of organic compounds in general by means of liquid chromatography-electrospray ionisation mass spectrometry (LC-ESI-MS), one should be aware of two major factors, which may strongly impact on the outcomes. These are directly associated with the process of ion generation in the interface. 

A novel approach in initial CDG diagnostics has currently been described by analysing the glycosylation state of serum transferrin using electrospray ionisation-tandem mass spectrometry (ESI-MS/MS). This method requires expensive technical... 

Many publications exist in the field of food analyses. Gerda Morlock described in 2004 the determination of heterocyclic aromatic amines after a 6-step AMD-separation. She used an HPTLC-MS online extractor, developed by Luftmarm [93a]. In 2004 a patent application was made for the mode of operation of this so-called ChromeXtrakt device [93b]. In her latest paper (2006), the quantification of isopropylthioxanthon (ITX) in food using HPTLC/FLD coupled with ESI-MS and DART-MS was reported. The prepared samples were separated on a HPTLC-plate and determined by a fluorescence detector (FLD). Positive results have been verified by ESI-MS (Electrospray-Ionisation-Mass-Spectrometry) and DART-MS (Direct Analysis in Real Trme-Mass-Spectrometry) [93c]. 

Automated in-tube solid-phase microextraction (SPME) has recently been coupled with liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS), e. g. for the determination of drugs in urine [60, 62]. In-tube SPME is an extraction technique in which analytes are extracted from the sample directly into an open tubular capillary by repeated draw/eject cycles of sample solution. The analyte is then desorbed with methanol and transferred to an analytical HPLC-column. 

HPLC-ESI-MS (Electrospray Ionisation mass spectrometry) uses a soft ionisation method, which yields the quasi molecular ion, in positive or negative ionisation mode or cation adducts, but a very restricted amount of fragmentation. The identification of unknown compounds is a major challenge in plant metab-... 

Mass spectroscopy [electron ionisation (El), chemical ionisation (Cl), electrospray ionisation (ESI), fast atom bombardment (FAB), matrix-associated laser desorption ionisation (MALDI), inductively coupled plasma-mass spectrometry (ICP-MS)... 

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