Alternative Abundance Generating Functions

The examples discussed above refer to adduct ion formation, where covalent bonds are formed in the Cl plasma. However, with the increasing importance of alternative ionization techniques, such as thermospray (TSI) and, in particular, electrospray ionization (ESI), a wealth of non-covalent ion/molecule adduct ions can be generated and studied nowadays. One recent example concerns the formation of ion/solvent adducts, [M- -So]+, with M including 3-aminophenol, 3-(methylamino)phenol and 3-(dimethylamino)phenol, and several hydroxypyrimidines, among other aromatic molecules. The relative abundances of ions [M- -H]+, [M -h So -h H]+ and [M - - 2 So - - H]+ were studied as a function of the temperature and the pH, with the solvents being mixtures of methanol/water and acetonitrile/water which may contain ammonium acetate as an additive . Quite in contrast to this empirical study on proton-bound ion/molecule complexes, the non-covalent, open-shell adduct ions [l + -h NH3] were investigated with respect to their intrinsic reactivity. These adduct ions were generated from phenol and ammonia by laser ionization of a... 

In addition to its protonating function, the NH4 ion can solvate the sample molecules [reaction (b) above], producing an abundant [M + 18] peak for some natural product classes (particularly carbohydrates and their derivatives). Ammonia is now well established in such cases as an alternative to methane and isobutane as a positive Cl reagent gas (9). Nitrous oxide has also been used with success to generate abundant [M + NO] ions from a variety of compounds, including natural terpenes 10). The fragmentations were characteristic. 

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