Multiply charged species

The spark source is an energetic ionization process, producing a rich spectrum of multiply charged species (Af/2, Af/3, Af/4, etc.). These masses, falling at halves, thirds, and fourths of the unit mass separation can aid in the positive identification of elements. In Figure 2, species like Au and are labeled. The most abundant... 

What multiple charging does not do, however, is to provide an equivalent increase in the resolution of the mass spectrometer and the resolution required to separate the individual isotopic contributions from a multiply charged species is identical to that required for the corresponding singly charged species. Figures 4.16 and 4.17 show the ions from the 7- - charge state of aprotin at resolutions of 1500 and 5000, respectively. 

AB cements are not only formulated from relatively small ions with well defined hydration numbers. They may also be prepared from macromolecules which dissolve in water to give multiply charged species known as polyelectrolytes. Cements which fall into this category are the zinc polycarboxylates and the glass-ionomers, the polyelectrolytes being poly(acrylic acid) or acrylic add copolymers. The interaction of such polymers is a complicated topic, and one which is of wide importance to a number of scientific disciplines. Molyneux (1975) has highlighted the fact that these substances form the focal point of three complex and contentious territories of sdence , namely aqueous systems, ionic systems and polymeric systems. 

Together with singly charged ions doubly and multiply charged ions may also arise in the ionization process. However, the number of doubly charged and especially of multiply charged species is much lower. The yield of these ions depends on the structure of a molecule and on the experimental conditions. For example, polycyclic aromatic hydrocarbons give more ions of these types compared to aliphatic or monoaromatic compounds. 

Multiply charged species can be seen when using ESI. In positive ion mode, the number of charged species normally observed is determined by the number of basic sites on a molecule that can be protonated at low pH. Singly charged species will show isotopic peaks that differ by 1 mass unit doubly charged ions show isotopic peaks that differ by 0.5 mass units. 

Another cause of error is the intrinsic mobility of multiply charged species. The mobility of doubly charged species is not always double the mobility of a single-charged species, as is the case with betahistine (14). Although some groups used this invalid assumption (18,28), this is one cause error. 

Multiply charged species require interpretation and mathematical transformation... 

Atmospheric pressure chemical ionisation (APCI, Fig. 16.21c) is a high sensitivity process that can also lead to the presence of multiply charged species (M + nH)n+. 

Mass spectrometric techniques also enable experimentalists to react dications and trications with neutral substrates in the gas phase to explore the chemical reactions of these multiply charged species. Although only a few superelectrophiles have thus far been examined experimentally for their gas phase chemical reactivities, other electrophilic gas phase reactions have demonstrated the potential of these methods. For example, the... 

There is no question that positively charged halogens exist and their associated energies are well-established the energies needed to convert the atomic halogens F, Cl, Br and I into the cations F+, Cl+, Br+ and I+ as well as a plethora of multiply charged species are well-... 

The formation and reaction of multiply-charged ions may occur more generally with other large molecules in IS and CS regions. For example, naphthalene, a member of the PAH family, has been shown to be doubly-ionized by thermal reaction with He+ [126]. The chemistry of such multiply-charged species remains to be explored, particularly with regard to their role in the ion-assisted synthesis of neutral molecules. 

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