MS" ICR

MS/MS analysis with ion storage mass spectrometers. Ion formation, selection, collision-induced decomposition and acquisition of the product ion spectrum take place in the same location of the mass spectrometer but sequentially in time, for example, ion trap MS, ICR MS. 

ICP/MS. inductively coupled plasma and mass spectrometry used as a combined technique ICR. ion cyclotron resonance (spectroscopy)... 

Instruments are available that can perform MS/MS type experiments using a single analyzer. These instruments trap and manipulate ions in a trapping cell, which also serves as the mass analyzer. The ion trap and fourier transform ion cyclotron resonance (FT-ICR) mass spectrometers are examples. 

Tandem quadrupole and magnetic-sector mass spectrometers as well as FT-ICR and ion trap instruments have been employed in MS/MS experiments involving precursor/product/neutral relationships. Fragmentation can be the result of a metastable decomposition or collision-induced dissociation (CID). The purpose of this type of instrumentation is to identify, qualitatively or quantitatively, specific compounds contained in complex mixtures. This method provides high sensitivity and high specificity. The instrumentation commonly applied in GC/MS is discussed under the MS/MS Instrumentation heading, which appears earlier in this chapter. 

Identification of unknowns using GC/MS is greatly simplified if accurate mass measurements are made of all the ions in a spectrum so that reasonable elemental compositions of each ion are available. Unfortunately, obtaining a mass measurement that is accurate enough to significantly limit the number of possible elemental compositions requires expensive instrumentation such as a double-focusing magnetic sector or fourier transform ICR MS. 

B. Asamoto (ed.), FT-ICR/MS Applications of Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, VCH Publishers, New York, NY (1991). 

Various analyzers have been used to analyze phenolic compounds. The choice of the MS analyzer is influenced by the main objective of the study. The triple quadrupole (QqQ) has been used to quantify, applying multiple reaction monitoring experiments, whereas the ion trap has been used for both identification and structure elucidation of phenolic compounds. Moreover, time-of-flight (TOF) and Fourier-transform ion cyclotron resonance (FT-ICR) are mainly recommended for studies focused on obtaining accurate mass measurements with errors below 5 ppm and sub-ppm errors, respectively (Werner and others 2008). Nowadays, hybrid equipment also exists, including different ionization sources with different analyzers, for instance electrospray or atmospheric pressure chemical ionization with triple quadrupole and time-of-flight (Waridel and others 2001). 

A mass spectrum may be obtained using this equation by a process termed mass linearization. The FT-ICR/MS differs from other MS techniques by nondestructive observation of the ions. The FT-ICR/MS has been the subject of several books and reviews. For a more complete discussion, the reader is directed to (28-30). 

The FT-ICR/MS is an ideal instrument for studying ion-molecule reactions over an extended time scale due to the excellent trapping of ions in the cell and the unmatched mass resolution and mass accuracy. Mass resolution is defined as the mass divided by the peak width at half height... 

Niobium and rhodium cluster anions have been prepared by laser vaporization and the reactions with benzene studied by FT-ICR/MS (58). The reactions of the anions and similar cations have been compared. With few exceptions the predominant reaction of the niobium cluster anions and cations was the total dehydrogenation of benzene to form the metal carbide cluster, [Nb C6]-. The Nb19 species, both anion and cation, reacted with benzene to form the coordinated species Nb 9C6I I6p as the predominant product ion. The Nb22 ions also formed some of the addition complex but the Nb2o Nb2i, and all the other higher clusters, formed the carbide ions, Nb C6. ... 

Freiser and co-workers (241) measured the kinetics of addition of [Ti8C12]+ with H20, NH3, MeCN, C6H6, and QH4. These measurements were carried out in a FT-ICR/MS at pressures of between 10 5 and 10 6 Pa. Even at these reduced pressures, the reactions could be studied for several seconds and up to seven H20 molecules could be observed to add to [Ti8C12]+. The addition of six NH3 molecules and four MeCN molecules were also observed. Four benzene and three ethene molecules... 

Capillary electrophoresis (CE) either coupled to MS or to laser-induced fluorescence (LIF) is less often used in metabolomics approaches. This method is faster than the others and needs a smaller sample size, thereby making it especially interesting for single cell analysis [215] The most sensitive mass spectrometers are the Orbitrap and Fourier transform ion cyclotron resonance (FT-ICR) MS [213]. These machines determine the mass-to-charge ratio of a metabolite so accurate that its empirical formula can be predicted, making them the techniques of choice for the identification of unknown peaks. 

Particular measurement tools face further problems. FT-ICR will have to overcome ion-ion interferences at high concentrations. As noted above, LC-MS can be subject to matrix effects, such as the presence of nonvolatiles. 

Although the above mass spectrometric tools have mass ranges and resolving powers adequate for chemical analysis, mass spectral characterization and structural analysis of biopolymers generally demand efficient detection of ions over a wide mass range, accurate mass measurements, and high mass resolution. The FT-ICR analyzer is able to combine high resolution and MS" capabilities. ... 

In principle, mass spectrometry is not suitable to differentiate enantiomers. However, mass spectrometry is able to distinguish between diastereomers and has been applied to stereochemical problems in different areas of chemistry. In the field of chiral cluster chemistry, mass spectrometry, sometimes in combination with chiral chromatography, has been extensively applied to studies of proton- and metal-bound clusters, self-recognition processes, cyclodextrin and crown ethers inclusion complexes, carbohydrate complexes, and others. Several excellent reviews on this topic are nowadays available. A survey of the most relevant examples will be given in this section. Most of the studies was based on ion abundance analysis, often coupled with MIKE and CID ion fragmentation on MS " and FT-ICR mass spectrometric instruments, using Cl, MALDI, FAB, and ESI, and atmospheric pressure ionization (API) methods. 

---