Subtractive phase Subject

Until now it was assumed that interaction between currents is absent, i.e. all currents induced in a conducting nonuniform medium, regardless of the distance from the source, are shifted in phase by 90°. For this reason electromotive forces induced in measuring coils of a probe are in phase with each other, and they are added and subtracted in the same way as scalars. If only one component of the electromotive force, for instance the quadrature component, is measnred it is subjected to the same operations as scalars, regardless of whether currents are shifted in phase by 90°, or the internal skin effect manifests itself and due to it at every point of a medium there are both quadrature and inphase components of the induced current. 

Ionization of the analyte is the first crucial and challenging step in the analysis of any class of compounds by mass spectrometry. The key to a successful mass spectrometric experiment lies to a large extent in the approach to converting a neutral compound to a gas-phase ionic species. A wide variety of ionization techniques have become available over the years, but none has universal appeal. In some techniques, ionization is performed by ejection or capture of an electron by an analyte to produce a radical cation [M+ ] or anion [M ], respectively. In others, a proton is added or subtracted to yield [M - - H]+ or [M — H] ions, respectively. The adduction with alkali metal cations (e.g., Na+ and K+) and anions (e.g., Cl ) is also observed in some methods. The choice of a particular method is dictated largely by the nature of the sample under investigation and the type of information desired. Table 2.1 lists some of the methods currently in vogue. Some methods are applicable to the atomic species, whereas others are suitable for molecular species. Also, some methods require sample molecules to be present in the ion source as gas-phase species, whereas others can accommodate condensed-phase samples. The methods that are applicable to molecular species are the subject of the present chapter those applicable to atomic species are described in Chapter 7. 

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