A novel chemical ionization reagent ion for organic analytes: the aquachloromanganese(II) cation [ClMn(H₂O)⁺]

Abstract

The reactivity of ClMn(H(2)O)(+) towards small organic compounds (L) was examined in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The organic compounds studied are aliphatic and aromatic alcohols, aliphatic amines, ketones, an epoxide, an ether, a thiol and a phosphine. All the reactions lead to the formation of the ClMn(H(2)O)(L)(+) complex, which dissociates by loss of the H(2)O molecule. In general, the reactions were found to occur with high efficiencies (>85%), indicating them to be exothermic. Electron transfer was also observed between ClMn(H(2)O)(+) and compounds with low ionization energies (IE), to form the molecular ion (L(+•)) of the analyte. Based on these observations, the IE of ClMn(H(2)O)(+) is approximated to be 8.1 ± 0.1 eV. Thus, the utility of ClMn(H(2)O)(+) as a chemical ionization reagent in mass spectrometry is expected to be limited to organic compounds with IEs greater than 8 eV.

Gas-phase reactions of a novel chemical ionization reagent, ClMn2+, with polar and nonpolar analytes in a linear quadrupole ion trap

“…This is true even for branched alkanes, such as 2,3-dimethylpentane (Table 1), which have been shown to fragment by CÀ ÀC bond cleavages upon ionization with other fairly gentle reagent ions, such as CpCo + [22]. Further, this also applies to analytes with low ionization energies [23] (IE; e.g., triethyl amine, IE = 7.5 eV; Table 2), which undergo [8] electron transfer with ClMn(H 2 O) + to produce molecular ions in addition to the desired adducts with ClMn + . Fig.…”

“…Examination of the reaction of an equimolar mixture of tetrahydrofuran and benzene yielded the same conclusions. Since the ClMn(H 2 O) + reactions reported previously [8] were performed in a different instrument(FT-ICR) from those used here, the reaction of triethylamine with ClMn(H 2 O) + was repeated in the LQIT in order to test whether similar reactivity is observed. Fig.…”

“…Electrospray ionization (ESI) and traditional atmospheric pressure chemical ionization (APCI) ionize preferentially the most basic or most acidic analytes. In contrast, the aquachloromanganese(II) cation [ClMn(H 2 O) + ] has been previously reported to enable efficient ionization of both polar and nonpolar analytes, including highly branched saturated hydrocarbons, via formation of a ClMn + adduct without accompanying fragmentation [6][7][8]. Coupling the ClMn(H 2 O) + reagent ion withlaser-induced acoustic desorption (LIAD) enabled mass spectrometric analysis of analytes previously inaccessible to such analysis, such as saturated nonpolar hydrocarbons in base oil fractions [7].…”

“…Coupling the ClMn(H 2 O) + reagent ion withlaser-induced acoustic desorption (LIAD) enabled mass spectrometric analysis of analytes previously inaccessible to such analysis, such as saturated nonpolar hydrocarbons in base oil fractions [7]. However, ClMn(H 2 O) + was found to ionize analytes with ionization energies less than 8 eV by electron transfer [8]. Therefore, this reagent is not suited for analysis of mixtures containing analytes with low ionization energies.…”

“…In order to address this issue,gas-phase reactions of two new, less aggressive reagent ions, ClMn 2 + and Mn + , were studied. The previous studies on the reagent ion ClMn(H 2 O) + were carried out using an obsoleteFourier-transform ion cyclotron resonance mass spectrometer(FT-ICR) [6][7][8]. In the study discussed here, a commercially available LQIT and a custom built dual linear quadrupole ion trap [9] (DLQIT) were used in order to take advantage of the faster duty cycles of the LQIT [10].…”