Fourier-transform mass spectrometry FTMS

The laser desorption experiments which we describe here utilize pulsed laser radiation, which is partially absorbed by the metal substrate, to generate a temperature jump in the surface region of the sample. The neutral species desorbed are ionized and detected by Fourier transform mass spectrometry (FTMS). This technique has... 

Laser desorption methods (such as LD-ITMS) are indicated as cost-saving real-time techniques for the near future. In a single laser shot, the LDI technique coupled with Fourier-transform mass spectrometry (FTMS) can provide detailed chemical information on the polymeric molecular structure, and is a tool for direct determination of additives and contaminants in polymers. This offers new analytical capabilities to solve problems in research, development, engineering, production, technical support, competitor product analysis, and defect analysis. Laser desorption techniques are limited to surface analysis and do not allow quantitation, but exhibit superior analyte selectivity. 

To overcome this, instrumental techniques such as pulsed high-pressure mass spectrometry (PHPMS), the flowing afterglow (FA) and allied techniques like the selected-ion flow tube (SIFT), and ion cyclotron resonance (ICR) spectrometry and its modem variant, Fourier transform mass spectrometry (FTMS), have been developed. These extend either the reaction time (ICR) or the concentration of species (PHPMS, FA), so that bimolecular chemistry occurs. The difference in the effect of increasing the pressure versus increasing the time, in order to achieve bimolecular reactivity, results in some variation in the chemistry observed with the techniques, and these will be addressed in this review as needed. 

Fourier Transform MS Fourier transform mass spectrometry (FTMS), which is a modem manifestation of ion cyclotron resonance, relies on the collection of ions in a high-vacuum cell and containment with a magnetic field. The ions orbit about the magnetic field axis. The ion masses and... 

Fourier transform mass spectrometry (FTMS) is a rapidly growing technique of increasing analytical importance. Foremost among its many attributes are its high mass resolution and wide mass range capabilities, as well as its ability to store ions. This relatively new technique has been employed in a wide variety of applications, ranging from the exact mass measurement of stable nuclides to the determination of peptide sequences. The future holds considerable promise both for the expanded use of FTMS in a diverse range of chemical problems, as well as advances in the capabilities of the technique itself. 

Although there are many attractive features of Fourier transform mass spectrometry (FTMS), there are problems with current implementations. The FT mass spectrometer is still a relatively young instrument when compared to the double-focussing mass spectrometer, and comparisons of the spectrometers and their... 

The theory and instrumentation of Fourier transform mass spectrometry (FTMS) have been discussed extensively in this book and elsewhere [21-23]. All experiments were performed on a Nicolet prototype FTMS-1000 Fourier transform mass spectrometer previously described in detail [24] and equipped with a 5.2 cm cubic trapping cell situated between the poles of a Varian 15 in. electromagnet maintained at 0.85 T. The cell was constructed in our laboratory and utilizes two 80 transmittance stainless steel screens as the transmitter plates. This permits irradiation with a 2.5 kW Hg-Xe arc lamp, used in conjunction with a Schoeffel 0.25 m monochromator set for 10 nm resolution. Metal ions are generated by focusing the beam of a Quanta Ray Nd YAG laser (either the fundamental line at 1064 nm or the frequency doubled line at 532 nm) into the center-drilled hole (1 mm) of a high-purity rod of the appropriate metal supported on the transmitter screen nearest to the laser. The laser ionization technique for generating metal ions has been outlined elsewhere [25]-... 

FT-ICR, first developed more than a decade ago (Comisarow and Marshall, 1974a,b), has become very popular in recent years for both analytical and ion/molecule reaction studies. In the literature this method is also frequently termed Fourier transform mass spectrometry (FTMS). The term FT-ICR, however, indicates the physical principles of the method more precisely and is less confusing the mathematical operation of Fourier transformation can also be applied to some other forms of mass spectrometry such as time-of-flight mass spectrometry as has been demonstrated recently (Knorr et al., 1986). 

Fourier transform mass spectrometry (FTMS) was first described by Comisarow and Marshall in 1974 [59,60] and was reviewed by Amster [61] in 1996 and by Marshall et al. [62] in 1998. This technique consists of simultaneously exciting all of the ions present in the cyclotron by a rapid scan of a large frequency range within a time span of about 1 ps. This induces a trajectory that comes close to the wall perpendicular to the orbit and also puts the ions in phase. This allows transformation of the complex wave detected as a time-dependent function into a frequency-dependent intensity function through a Fourier transform (FT), as shown in Figures 2.60 and 2.61. 

Electrospray ionization with the high resolving power of Fourier transform mass spectrometry (FTMS) makes possible the detection of adducts and subpicomole impurities that confuse lower resolution measurements, as shown in Figure 8.30. This method achieves accurate determination of molecular weights (<0.002 %) and permits the verification of 50-100-mer DNA and RNA sequences. [169,170]... 

Trypsin digests of both wild type HRV virus and the mutant were analyzed using MALDI-TOF and MALDI Fourier transform mass spectrometry (FTMS). For HRV, the mass spectra for both wild-type and mutant were identical except for one peptide occurring at mlz 4700. This corresponds to residues 187-227 in the wild type sequence. The corresponding peak in the mutant mass spectrum occurs at 4783.5 (Fig. 4, inset). This mass difference of 83 Da corresponds exactly to a mutation of a Cys to Trp residue and there are no other possible mutations that would be separated by 83 Da. Since there is only one Cys in the peptide 187-227 at position 199, the mutant can be localized as HRV14-Cysl99Trp, which contains a Trp at position 199 instead of Cys in the wild type. 

Considerable insight about fundamental aspects of the behavior of simple Ge, Sn and Pb species can be obtained from studies aimed at characterizing the reactivity of gas-phase ions. Reactions of the primary ions obtained by electron ionization of GelTj with the neutral monogermane precursor have been characterized both by low- and high-pressure mass spectrometric techniques , and more recently by ion trap techniques (ITMS). The ability to select a particular isotopic species (usually the Ge-containing ion) in low pressure studies carried out by Fourier Transform Mass Spectrometry (FTMS) has been essential in understanding the mechanism of these processes. The main results can be summarized as follows ... 

The first step is the priming of the NRPS active site and a subsequent limited tryptic digest of the protein. The digested sample is loaded on a reverse-phase liquid chromatography (RPLC) C18 column, which is directly connected to the inlet of an FT mass spectrometer. During online LC separation, the eluent is analyzed by MS and MS2 on an LC timescale. In the mass spectrometer the eluent is first analyzed by broadband Fourier transform mass spectrometry (FTMS). Then, peaks in the resulting broadband FT mass spectrum are... 

In this review we discuss five techniques involving Fourier transform mass spectrometry (FTMS) for determining qualitative and quantitative metal ion-ligand bond energies. These include (i) exothermic ion-molecule reactions, (ii) equilibrium measurements, (iii) competitive collision-induced dissociation, (iv) endothermic ion-molecule reactions, and (v) photodissociation. A key advantage of the FTMS methodology is its ion and neutral manipulation capabilities which permit the formation and study of a limitless number of interesting metal-ion systems. 

The combination of laser ionization and Fourier transform mass spectrometry (FTMS) has proved to be ideally suited for the study of gas-phase ion-molecule reactions involving metal ions (1-7). The laser source permits the generation of virtually any metal ion in the periodic table from a suitable metal target (8). The FTMS (9-14) stores these ions in an "electro-magnetic bottle" for times t)rpically on the order of msec to sec (hours are possible) permitting the study of their chemistry and photochemistry. These studies are further facilitated by the unusual ion and neutral manipulation capabilities of the FTMS which permit complex multistep processes to be monitored in an MS fashion (1-4). These capabilities have made laser ionization-FTMS a prominent method in what has been a rapidly growing arsenal of techniques for studying gas-phase transition-metal ion species. 

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