Application of alkali ions in chemical ionization mass spectrometry

Sodium ion attachment reactions in an ion trap mass spectrometer

“…3(b)). The use of Na + to detect species at the partial pressure provided in the ion trap for these experiments has shown that the minimum enthalpy variation required for reaction (1) lies in the same range as the energy required for binding (specified earlier) in the case of lithium cation attachment reactions 13. Taking into account the differences in binding energy between Na + and Li + with most of the organic compounds, nitromethane appeared to be the lowest bound adduct detected.…”

“…The binding energy of the reagent alkali ion A + to the molecule B is an important parameter in choosing the alkali ion; it must be high enough to permit a significant number of adducts to be formed at the partial pressure used in the experiments. Such use of alkali cations as reagent species for CI mass spectrometry has been investigated previously 13,. 14 The relative binding energies of a large number of molecules have been measured and correlated with theoretical calculations.…”

“…The results have indicated that the ion binding energies of a wide range of alkali ion complexes are high enough to be detectable at low concentrations as long as the attachment process is kinetically efficient 9,. 12,, 15 It was initially proposed that enthalpies of binding exceeding 21 kcal.mol −1 were desirable for sampling under analytical conditions (typically, with analytes at a partial pressure in the 10 −7 Torr range in a bath gas at 10 −1 Torr, as demonstrated for lithium ion attachment reactions13). More recently, enthalpies ΔH ° and free‐energies ΔG ° for reaction 1 have been reassessed, with lower absolute values established for several organic molecules in the case of lithium or sodium adduction 12,.…”

Development of a tabletop time‐of‐flight mass spectrometer with an ion attachment ionization technique

“…A new CI method – the ion attachment (IA) method – has been evaluated 2, 3. In IA, an alkali metal ion A + attaches to a sample molecule M. These ion association reactions are describes as follows: …”

Resonant laser ablation as a selective metal ion source for gas-phase ion molecule reactions

“…ass spectrometric investigations of the gasphase chemistry of metal ions have been conducted since the early 1970s. Early studies [1][2][3][4][5][6][7][8] involved the use of thermionic emitters for metal ion production and mass spectrometers for reaction and product analysis. Subsequent investigations led to the exploitation of alkali and transition metal ions as chemical ionization (Cl) reagents for aliphatic molecules.…”