Mass spectrometry ionized particles

Secondary ion (mass spectrometry) SIMS Particle induced desorption/ ionization Nonvolatile molecular ions Semiconductors Surface analysis Imaging... 

FIGURE 11.72 Negative ion laser ionization mass spectrometry of particles generated in the laboratory that contain equimolar amounts of NaCI, NH4N03, (NH4)2S04, and CH3S03H at (a) 7%, (b) 40%, and (c) 83% relative humidity (adapted from Neubauer et al., 1998). 

Coupling of liquid chromatography with mass spectrometry provides unequivocal online spectrometric identification of tetracycline antibiotics in animal-derived foods. Typical applications of mass spectrometry in confirming tetracycline residues in edible animal products describe coupling of liquid chromatography with mass spectrometry via particle-beam (280), electrospray (292), or atmospheric pressure chemical ionization (307), using negative-ion detection interfaces. 

FL fluorescence DAD diode array detector UV UV detector MS mass spectrometry PB particle beam interface TSP thermospray interface ESI electrospray ionization EC electrochemical detection CV cyclic voltammetry MAECFD micro-array electrochemical flow detector DL detection limit Rec recovery RSD relative standard deviation... 

There is no systematic study of mass spectra of azoniaspiroalkanes. Mass spectra of Prospidine and related compounds (22), using secondary emission spectroscopy, have been reported <90OMS(25)432, 91KFZ78>. A minor adduct from prospidine and deoxyguanosine-5 -phosphate has been studied by soft-ionization mass spectrometry (Cf particle desorption mass spectrometry— PDMS) <94RCM195, 94MI 840-01 >. 

Crecelius, A., Clench, M.R., Richards, D.S., and Parr, V. 2002. Thin-layer chromatography-matrix-assisted laser desorption ionization-time-of-flight mass spectrometry using particle snspension matrices, J. Chromatogr. A, 958 249-260. 

Static Secondary Ion Mass Spectrometry (SIMS) involves the bombardment of a sample with an energetic (typically 1-10 keV) beam of particles, which may be either ions or neutrals. As a result of the interaction of these primary particles with the sample, species are ejected that have become ionized. These ejected species, known as secondary ions, are the analytical signal in SIMS. 

See footnote cto Table3 LC/PB/MS = hquid chromatography/particle beam mass spectrometry LC/APcl/ESl-MS/MS = liquid chromtography/atmospheric pressure chemical ionization/electrospray ionization tandem mass spectrometry LC/FTIR = Fourier transform infrared LC/TSP-MS/MS = liquid chromatography/thermospray tandem mass spectrometry LC/TSP-MS = liquid chromatography/thermospray mass spectrometry. 

Cochran JK, Masque P (2003) Short-lived U/Th-series radionuclides in the ocean tracers for scavenging rates, export fluxes and particle dynamics. Rev Mineral Geochem 52 461-492 Cohen AS, O Nions RK (1991) Precise determination of femtogram quantities of radium by thermal ionization mass spectrometry. Anal Chem 63 2705-2708 Cohen AS, Belshaw NS, O Nions RK (1992) High precision uranium, thorium, and radium isotope ratio measurements by high dynamic range thermal ionization mass spectrometry. Inti J Mass Spectrom Ion Processes 116 71-81... 

Figure 7.28 Typical particle-beam interface. After Ashcroft [524]. From A.E. Ashcroft, Ionization Methods of Organic Mass Spectrometry, The Royal Society of Chemistry, Cambridge (1997). Reproduced by permission of The Royal Society of Chemistry...

M. Schiirenberg, K. Dreisewerd, and F. Hillenkamp, Laser Desorption/Ionization Mass Spectrometry of Peptides and Proteins with Particle Suspension Matrices, Anal. Chem., 71, 221 229(1999). 

By employing a laser for the photoionization (not to be confused with laser desorption/ ionization, where a laser is irradiating a surface, see Section 2.1.21) both sensitivity and selectivity are considerably enhanced. In 1970 the first mass spectrometric analysis of laser photoionized molecular species, namely H2, was performed [54]. Two years later selective two-step photoionization was used to ionize mbidium [55]. Multiphoton ionization mass spectrometry (MPI-MS) was demonstrated in the late 1970s [56—58]. The combination of tunable lasers and MS into a multidimensional analysis tool proved to be a very useful way to investigate excitation and dissociation processes, as well as to obtain mass spectrometric data [59-62]. Because of the pulsed nature of most MPI sources TOF analyzers are preferred, but in combination with continuous wave lasers quadrupole analyzers have been utilized [63]. MPI is performed on species already in the gas phase. The analyte delivery system depends on the application and can be, for example, a GC interface, thermal evaporation from a surface, secondary neutrals from a particle impact event (see Section 2.1.18), or molecular beams that are introduced through a spray interface. There is a multitude of different source geometries. 

Based on a new technology, particle beam enhanced liquid chromatography-mass spectrometry expands a chemist s ability to analyse a vast variety of substances. Electron impact spectra from the system are reproducible and can be searched against standard or custom libraries for positive compound identification. Chemical ionization spectra can also be produced. Simplicity is a key feature. A simple adjustment to the particle beam interface is all it takes. 

Ionization may take place by the interaction with a particle sufficiently high in energy, e.g. an electron or a photon, or by the addition of charged species, e.g. an electron or a proton. The thermochemistry associated with the ionization process provides information on ion structures, since a structure may be assigned based on heat of formation when compared to data of reference ions. Thus, the determination of ionization energy, electron affinity and proton affinity plays a central role in mass spectrometry. 

Traditionally thermal ionization mass spectrometry was the instrument of choice for the isotopic analysis of metals because thermal ionization produced an ion beam with a very small kinetic energy spread ( 0.5 eV). Therefore only a magnetic mass analyzer is needed to resolve one isotope from another. Moreover, ionization of unwanted material, such as atmospheric contaminates, hydrocarbons from pump oil, or production of doubly ionized particles is almost non existent, thus background counts are minimized and signal-to-noise ratio is maximized. 

Fig. 9.4. Simple illustration of an instantaneous collision cascade generated as a result of primary particle impact in desorption/ionization mass spectrometry. Adapted from Ref. [24] by permission. John Wiley Sons, 1995.

Groenewold, G.S., A.D. Appelhans, G.L. Gresham, and J.E. Olson, J. Jeffery, and J.B. Wright. 1999. Analysis of VX on soil particles using ion trap secondary ionization mass spectrometry. Analytical Chemistry 71 2318-2323. 

Interfacing of solution-based separation techniques with mass spectrometry has historically been a challenge because of the incompatibility of the used solvent with the vacuum system. Standard electron impact (El) ionization with techniques such as particle beam require samples to be vaporized under high vacuum for ion formation to occur. 

Even if relatively new, HF FIFFF has been used to separate supramicrometer particles, proteins, water-soluble polymers, and synthetic organic-soluble polymers. Particle separation in HF FIFFF has recently been improved, reaching the level of efficiency normally achieved by conventional, rectangular FIFFF channels. With these channel-optimized HF FIFFF systems, separation speed and the resolution of nanosized particles have been increased. HF FIFFF has recently been examined as a means for off-line and on-line protein characterization by using the mass spectrometry (MS) through matrix-assisted laser desorption ionization time-of-flight mass spectrometry (M ALDl-TOF MS) and electrospray ionization (ESl)-TOF MS, as specific detectors. On-line HF FIFFF and ESl-TOF MS analysis has demonstrated the viability of fractionating proteins by HF FIFFF followed by direct analysis of the protein ions in MS [38]. 

Great care has to be taken in the analytical characterization of synthetic cyclic peptides.[73] The major side reactions during cyclization are epimerization of the C-terminal amino acid residue and cyclodimerization. Cyclodimers can be detected by mass spectrometry, although the analysis is not trivial, because artifacts do occur in some ionization techniques such as ES-MS as a result of aggregation.1 1 Ll 121 Real dimers can be detected as double-charged particles with mlz values identical to the cyclic monomers, but with a mass difference of 0.5 amu in the resolved isotope signals. The mass difference of the corresponding monomer is 1 amu. The cyclodimerization has received some attention as a direct method for the synthesis of C2-symmetrical cyclic peptides.[62 67 94113 115]... 

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