Spectrometers, quadrupole mass

ToF mass spectrometers as dynamic instruments gained popularity with the introduction of matrix assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) as effective pulsed ion sources for the soft ionization of large biomolecules (up to 10s dalton) due to their high ion transmission.38 ToF mass spectrometers, quadrupole analyzers and/or magnetic sector fields can be combined in tandem mass spectrometers (MS/MS) for the analysis of organic compounds. 

At present GDMS164 165 is one of the most powerful solid-state analytical methods for the direct determination of trace impurities and depth profiling of solids. The positively charged ions formed in the low pressure argon plasma of the glow discharge are extracted and accelerated into the double-focusing sector field mass spectrometer, quadrupole, ion trap or ToF mass analyzer. 

Due to the pulsed nature of most of these experiments, much of the work to date has been performed using time-of-flight mass spectrometers. Quadrupole mass spectrometers are also well suited, especially with higher duty cycle systems. Design of the instruments has followed conventional approaches, for which the resolution limits the size and complexity of the cluster and cluster-adduct species that can studied. One serious problem is the isotopic abundance of many of the metals, which serves to complicate mass spectra. Isotopi-cally pure materials, such as used in measurements of hydrogen uptake on Fe clusters, " simplify the mass spectra. Use of the reflectron time-of-flight mass spectrometer allows the study of metastable clusters and cluster adducts. Details of different instrument designs are described in the references. 

Time-of-flight mass spectrometers, quadrupole mass filters, and several types of magnetic-sector mass spectrometer have all been used in photoionization studies. Specific experiments may favor one or another of these types. Most experiments favor a mass spectrometer with high transmission and only modest mass resolution (e.g., 1/100). The time-of-flight mass spectrometer is not as generally useful as the other two types... 

Germany MM-1 Mobile Mass Spectrometer - Quadrupole mass spectrometric detection of chemical warfare agents Rapid Alarm and Identification Device -1 (RAID-1) - Ion mobility spectrometric detection of nerve and blister agents... 

Quadrupole mass spectrometer Quadrupole mass filter... 

The potential of the most commonly used mass spectrometers (quadrupoles and magnetic sector-field single collectors) for elemental analysis has been discussed in detail in Parts 2.1 and 2.2.1 of this chapter. However, some intrinsic limitations still remain with these sequentially scanned systems, particularly when transient or time-dependent signals (such as those produced by laser ablation (LA), electrothermal vaporisation (ETV), flow injection (FI) and chromatography) are used to analyse a large number of isotopes. These scan-based systems can measure only a single m/z at a unit of time. Hence, truly simultaneous determination of multiple isotopes, particularly when fast transient signals are analysed, is not possible without the introduction of spectral skew . ... 

---