Mass spectrometer applications

Lustig, S., Michalke, B., Beck, W. and Schramel, R (1998) Platinum speciation with hyphenated techniques high performance liquid chromatography and capillary electrophoresis on-line coupled to an inductively coupled plasma mass spectrometer -application to aqueous extracts from a platinum treated soil. Fresenius J. Anal. Chem., 360,18-23. 

F Chew, S Gronert, CB LebrUla. Preliminary studies of the reactions of peptide dianions in a mass spectrometer applications for sequencing. Proceedings of the 47th ASMS Conference on Mass Spectrometry and Allied Topics, Dallas, TX, 1999. 

Material Tooth enamel Instrumentation Mass spectrometer Application Provenience Place Mexico... 

Material Tooth enamel Instrumentation Mass spectrometers Application Place of birth Place Honduras... 

J. M. Ramsey, Microfabricated quadru-pole ion trap for mass spectrometer applications, Phys. Rev. Lett. 2006, 96, 120801. 

A potentially important application area for capillary SFC and SFC-MS is in the analysis of thermally labile molecules not readily amenable to gas chromatography, such as mycotoxins of the trichothecene group (48,49). Figure 14 shows a fast separation of four trichothecenes on a short 0.8 m x 25 pm column at 100 C with supercritical CO2 as the mobile phase. Diacetoxyscirpenol (DAS) and T-2 toxin are easily resolved while the two macrocyclic compounds, roridin A and verricarin J, are not well separated. However, even this level of separation is often sufficient given a highly selective detector such as the mass spectrometer. Application of SFC-MS to these compounds is described in detail elsewhere ( ). 

Sheath gas flow around the emitter orifice can be utilized when a stable electrospray in the cone-jet mode is difficult to achieve. One reason why a stable cone-jet mode electrospray can be difficult to obtain in a mass spectrometer application is an increased flow rate. An increase in flow rate causes the electrospray to operate outside the island of stability mentioned previously (Fig. 32.12). The effect that the sheath gas has on the electrospray is increased breakup of the spray droplets through the transfer of kinetic energy. 

FIGURE 12.2 Detection and measurement protocol using a quadrupole mass analyzer. (From Integrated MCA Technology in the ELAN I CP-Mass Spectrometer, Application Note TSMS-25, PerkinElmer Instruments, 1993.)... 

Integrated MCA Technology in the ELAN ICP-Mass Spectrometer, Application Note TSMS-25, PerkinEkner Instruments, 1993. 

Figure 5. Variable pressure soft ioniser for ion mobility and mass spectrometer applications using UV-LED excitation in LaB nanolayers...

Ryhage, R. (1967), Efficiency of molecule separators used in gas chromatograph-mass spectrometer applications. Ark. Kem., 26,305. 

In essence, a guided-ion beam is a double mass spectrometer. Figure A3.5.9 shows a schematic diagram of a griided-ion beam apparatus [104]. Ions are created and extracted from an ion source. Many types of source have been used and the choice depends upon the application. Combining a flow tube such as that described in this chapter has proven to be versatile and it ensures the ions are thennalized [105]. After extraction, the ions are mass selected. Many types of mass spectrometer can be used a Wien ExB filter is shown. The ions are then injected into an octopole ion trap. The octopole consists of eight parallel rods arranged on a circle. An RF... 

The mass spectrometer tends to be a passive instrument in these applications, used to record mass spectra. In chemical physics and physical chemistry, however, the mass spectrometer takes on a dynamic function as a... 

Time-of-flight mass spectrometers have been used as detectors in a wider variety of experiments tlian any other mass spectrometer. This is especially true of spectroscopic applications, many of which are discussed in this encyclopedia. Unlike the other instruments described in this chapter, the TOP mass spectrometer is usually used for one purpose, to acquire the mass spectrum of a compound. They caimot generally be used for the kinds of ion-molecule chemistry discussed in this chapter, or structural characterization experiments such as collision-induced dissociation. Plowever, they are easily used as detectors for spectroscopic applications such as multi-photoionization (for the spectroscopy of molecular excited states) [38], zero kinetic energy electron spectroscopy [39] (ZEKE, for the precise measurement of ionization energies) and comcidence measurements (such as photoelectron-photoion coincidence spectroscopy [40] for the measurement of ion fragmentation breakdown diagrams). 

Analytical chemistry has in recent years been equipped with a number of powerful means of investigation. Their application, especially that of gas-phase chromatography coupled with a mass spectrometer, has demonstrated the presence of a certain number of thiazoles in natural products such as fruits or cereals (287. 288, 297). The many results are shown in Table III-59. 

In many applications in mass spectrometry (MS), the sample to be analyzed is present as a solution in a solvent, such as methanol or acetonitrile, or an aqueous one, as with body fluids. The solution may be an effluent from a liquid chromatography (LC) column. In any case, a solution flows into the front end of a mass spectrometer, but before it can provide a mass spectrum, the bulk of the solvent must be removed without losing the sample (solute). If the solvent is not removed, then its vaporization as it enters the ion source would produce a large increase in pressure and stop the spectrometer from working. At the same time that the solvent is removed, the dissolved sample must be retained so that its mass spectrum can be measured. There are several means of effecting this differentiation between carrier solvent and the solute of interest, and thermospray is just one of them. Plasmaspray is a variant of thermospray in which the basic method of solvent removal is the same, but the number of ions obtained is enhanced (see below). 

Nebulizers are used to introduce analyte solutions as an aerosol spray into a mass spectrometer. For use with plasma torches, it is necessary to produce a fine spray and to remove as much solvent as possible before the aerosol reaches the flame of the torch. Various designs of nebulizer are available, but most work on the principle of interacting gas and liquid streams or the use of ultrasonic devices to cause droplet formation. For nebulization applications in thermospray, APCI, and electrospray, see Chapters 8 and 11. 

Modem mass spectrometers are used in a very wide variety of situations, so it is almost impossible to have a simple set of criteria that would determine whether a quadrupole or magnetic sector instmment would be best for any particular application. Nevertheless, some attempt is made here to address major considerations, mostly relating to cost. 

A major advantage of the TOF mass spectrometer is its fast response time and its applicability to ionization methods that produce ions in pulses. As discussed earlier, because all ions follow the same path, all ions need to leave the ion source at the same time if there is to be no overlap between m/z values at the detector. In turn, if ions are produced continuously as in a typical electron ionization source, then samples of these ions must be utihzed in pulses by switching the ion extraction field on and off very quickly (Figure 26.4). 

Accurate, precise isotope ratio measurements are important in a wide variety of applications, including dating, examination of environmental samples, and studies on drug metabolism. The degree of accuracy and precision required necessitates the use of special isotope mass spectrometers, which mostly use thermal ionization or inductively coupled plasma ionization, often together with multiple ion collectors. 

In field ionization (or field desorption), application of a large electric potential to a surface of high curvature allows a very intense electric field to be generated. Such positive or negative fields lead to electrons being stripped from or added to molecules lying on the surface. The positive or negative molecular ions so produced are mass measured by the mass spectrometer. 

In many applications of mass spectrometry, it is necessary to obtain a mass spectrum from a sample dissolved in a solvent. The solution cannot be passed directly into the mass spectrometer because, in the high vacuum, the rapidly vaporizing solvent would entail a large pressure increase, causing the instrument to shut down. 

Accurate, precise isotope ratio measurements are used in a variety of applications including dating of artifacts or rocks, studies on drug metabolism, and investigations of environmental issues. Special mass spectrometers are needed for such accuracy and precision. 

---