Ion Attachment-TOF System

The lA-TOF system mainly consists of an lA ion source, a differential pumping system, and a TOF mass spectrometer (Fig. 6.9). The main body of the lA-TOF sys- 

Ion attachment mass spectrometry (lAMS) has proven to be a rMque method that complements electron-impact ionization mass spectrometry for the determination of components in chemical processes and environments, such as microwave discharge plasma. The identification of intermediate free radicals and other species in chemical reactions is particularly challenging. One of the greatest advantages of lAMS is that it can be used to directly analyze gaseous compounds. The features that allow this system to detect the intermediate free radicals (refer to Sect. 5.2.4) and novel molecular species produced in various plasmas have been extensively explored (Sect. 5.2.7), and lAMS techniques can be used to identify and quantify compounds and mixtures under plasma and pyrolysis (Sect. 6.4) conditions. To extend the ion attachment technique to ion trap mass spectrometry (Sect. 6.5) or time-of-flight mass spectrometry (Sect. 6.6) has been realized. 

However, the conunercial lAMS apparatus is too cumbersome for use in field analysis of air samples. Unfortunately, the commercial apparatus is not practical for the study of atmospheric environments. Therefore, to develop a new, compact and fieldable lAMS system by eliminating the differential pumping stage is desirable. The primary objeetive for the development was to design a system that can be easily transported to the field and that can detect any chemical species at atmospheric pressirre on a real-time basis. A single turbomolecular pump is employed as the vacuirm system to fill the basic requirements for vacuum conditions this is simple and cost effective. The optimal operation parameters for its use, the details and operation of the capillary leak inlet, and the system s analytical power in some preliminary applications are described also in this section 

A compact ion attachment mass spectrometer was designed that is simple and small and fulfills all the basic requirements for lAMS the system can be used to obtain only molecular ions by detecting any chemical species in real time [93]. This custom-made apparatus (Fig. 6.11) consists of a Li+ ion attachment ion source into which a stream of gas from a capillary leak inlet is directed, an electrostatic lens system (ELS), and a quadrupole mass spectrometer and detector, all of which are installed in a vacuum-separated envelope. The system employs a single tuibomo-lecular pirmp on the vacuum envelope instead of a differential pumping system. 

The newly developed instrument has several important features. It accepts high capacity direct introduction of samples, operates with the atmospheric sampling device, and allows easy coupling of varions sample introduction sonrces to the mass spectrometer. It permits real-time detection of chemical species, possibly in-clnding radical intermediates and easy identification of compounds via the generation of ions that do not fragment. In addition, the capillary leak inlet system is simple and adaptable. In the near future, a large increase is expected in the use of lAMS for environmental and food chemistry research, especially in cases where 

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