TOF-MS

In 1984, the AMPTE mission launched the first carbon-foil TOF-MS into space, which would have been the second, had the Challenger shuttle disaster not delayed the Ulysses launch until 1991 (Fig. 11.2) [23]. The photons were filtered out by a traditional blackened deflection system, which directed the ions toward the 2 p,g/cm2 thick foil mounted on an 85% transparent grid almost a square centimeter in area. The grid provided the support needed to survive the launch. The foil thickness permitted 2keV/nuc ions to pass through and hit a SSD some 10 cm away. To ensure that the ions made it through the foil and also through the dead layer on the SSD (caused by the upper electrode), the foil and the entire TOF section were floated at 20 kV to post-accelerate the ions. Electrons sputtered off the carbon foil became the start, whereas electrons sputtered off the SSD became the stop pulse for the TOF. 

Energy Time-of-flight Deflection E/q Thin Foil l(2—3 ng/cm ). 

---

Two detection techniques were tested, LIBS for the Cu-Ag-Si samples and LA-TOF-MS for the TiN-TiAlN samples. 

The "soft" ablation of the TiN-TiAlN samples by the low fluence laser beam was performed by use of LA-TOF-MS. Because of the greater sensitivity of this technique compared with direct LIBS the lower laser fluence of approximately 0.3-0.4 J cm was used. One of the depth profiles, obtained by use of femtosecond LA-TOF-MS, is shown in Fig. 4.44. Each 280-nm-thick layer was ablated by approximately 20-25 pulses, which result in an average ablation rate of 11-14 nm pulse . The ablation rate was low enough for resolution of all layers. 

The crater surfaces obtained in the LA-TOF-MS experiment on the TiN-TiAlN-Fe sample were remarkably smooth and clearly demonstrated the Gaussian intensity distribution of the laser beam. Fig. 4.45 shows an SEM image of the crater after 100 laser pulses (fluence 0.35 J cm ). The crater is symmetrical and bell-shaped. There is no significant distortion of the single layers. Fig. 4.45 is an excellent demonstration of the potential of femtosecond laser ablation, if the laser beam had a flat-top, rather than Gaussian, intensity profile. 

Kato, S., Oba, Y., Ojika, M., and Inouye, S. (2004). Identification of the biosynthetic units of Cypridina luciferin in Cypridina (Vargula) hilgen-dorfii by LC/ESI-TOF-MS. Tetrahedron 60 11427-11434. 

The molecular weights and molecular weight distributions (MWD) of phenolic oligomers have been evaluated using gel permeation chromatography (GPC),23,24 NMR spectroscopy,25 vapor pressure osmometry (VPO),26 intrinsic viscosity,27 and more recently matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).28... 

During the past decade, MALDI-TOF MS has proven to be an effective tool for the analysis of oligo- and polymeric mannoglucans (for extensive reviews see [222,223]). SEC/MALDI mass spectrometry was employed in the analysis of hemicelluloses isolated by microwave heat-fractionation from spruce and aspen wood [94]. These methods allowed the separation and characterization of the oligo- and polysaccharide fractions derived from the xylan and mannan components of both woods [224]. 

Figure 5.31 LC-electrospray-MS-MS spectrum of the column eluate at around 22 min in the analysis of the peptide mixture from the tryptic digest of glycoprotein TIME-EA4 from silkworm diapause eggs. Reprinted from Bioorg. Med. Chem., 10, Kurahashi, T., Miyazaki, A., Murakami, Y., Suwan, S., Franz, T., Isobe, M., Tani, M. and Kai, H., Determination of a sugar chain and its linkage site on a glycoprotein TIME-EA4 from silkworm diapause eggs by means of LC-ESI-Q-TOF-MS and MS/MS , 1703-1710, Copyright (2002), with permission from Elsevier Science.

Figure 5.67 Reconstructed ion chromatograms for Idoxifene and internal standard (ds-Idoxifene using LC-ToF-MS for (a) double-blank human plasma extract, (b) extract of blank human plasma containing internal standard (IS), and (c) control-blank human plasma spiked with Idoxifene at 5 gml , the LOQ of the method. Reprinted from 7. Chromatogr., B, 757, Comparison between liquid chromatography-time-of-flight mass spectrometry and selected-reaction monitoring liquid chromatography-mass spectrometry for quantitative determination of Idoxifene in human plasma , Zhang, H. and Henion, J., 151-159, Copyright (2001), with permission from Elsevier Science.

Figure 5.69 Calibration curves obtained from (a) LC-ToF-MS and (b) LC-MS-MS using selected-reaction monitoring for Idoxifene in human plasma, fortified from 5 to 2000 ngml for LC-ToF-MS and 0.5 to 1000 ngml for LC-MS-MS with a triple quadrupole is the correlation coefficient, a measure of the quality of calibration (see...

Table 5.22 Comparison of method performance for LC-ToF-MS and LC-MS-MS determination of Idoxifene...

Scheme 3. J efro-addition of 23 and 24 under MALDI-TOF MS conditions generates the ions of the mono-fullerene adducts of cydo-Ci (25" ) and cydo-C.20 (26" ), respectively [61]...

Initial MALDI-TOF MS indicates that only two of the four bean sites have carbohydrate chains attached (data not shown). 

Figure 4.12 On-line coupling of the bifur-cation-distributive chip micro mixer to a Perseptive Biosystems Mariner TOF-MS [25],...

MALDI-TOF MS Matrix-Assisted Laser Desorption Ionisation... 

Scraping and elution NMR and MALDI-TOF/MS Scraping and elution Immimoassay... 

Anke, G. H., Thomas, M., Frank, G., Reiner, S., Helge, B., Markus, K., and Monika, K. (2008). Challenging the problem of clostridial identification with matrix-assisted laser desorption and ionization-time-of-fight mass spectrometry (MALDl-TOF MS). Anaerobe 14, 242-249. 

Maier, T., Klepel, S., Renner, U., and Kostrzewa, M. (2006). Fast and reliable MALDl-TOF MS-based microorganism identification. Nat. Methods 3, 1-2. 

FIGURE 10.5 (a) MALDI-TOF MS analysis of the apo-form of bovine Cu, Zn superoxide... 

Resolution does not affect the accuracy of the individual accurate mass measurements when no separation problem exists. When performing accurate mass measurements on a given component in a mixture, it may be necessary to raise the resolution of the mass spectrometer wherever possible. Atomic composition mass spectrometry (AC-MS) is a powerful technique for chemical structure identification or confirmation, which requires double-focusing magnetic, Fourier-transform ion-cyclotron resonance (FTICR) or else ToF-MS spectrometers, and use of a suitable reference material. The most common reference materials for accurate mass measurements are perfluorokerosene (PFK), perfluorotetrabutylamine (PFTBA) and decafluorotriph-enylphosphine (DFTPP). One of the difficulties of high-mass MS is the lack of suitable calibration standards. Reference inlets to the ion source facilitate exact mass measurement. When appropriately calibrated, ToF mass... 

---