Gross Jürgen H
Institute of Organic Chemistry, University of Heidelberg, Heidelberg, Germany.
J Am Soc Mass Spectrom. 2008 Sep;19(9):1347-52. doi: 10.1016/j.jasms.2008.06.002. Epub 2008 Jun 20.
Ionic liquids form neutral ion pairs (CA) upon evaporation. The softness of the gas-phase ionization of field ionization has been used to generate "molecular ions," CA(+), of ionic liquids, most probably by neutralization of the anion. In detail, 1-ethyl-3-methylimidazolium-thiocyanate, C(6)H(11)N(2) SCN, 1-butyl-3-methylimidazolium-tricyanomethide, C(8)H(15)N(2) C(4)N(3), N-butyl-3-methylpyridinium-dicyanamide, C(10)H(16)N C(2)N(3), and 1-butyl-1-methylpyrrolidinium-bis[(trifluormethyl)sulfonyl]amide, C(9)H(20)N C(2)F(6)NO(4)S(2) were used. The assignment as CA(+) ions, which has been confirmed by accurate mass measurements and misassignments due to thermal decomposition of the ionic liquids, has been ruled out by field desorption and electrospray ionization mass spectrometry of the residues.
离子液体在蒸发时会形成中性离子对（CA）。场电离的气相电离的柔和性已被用于产生离子液体的“分子离子”CA(+)，很可能是通过阴离子的中和作用。具体而言，使用了1-乙基-3-甲基咪唑鎓硫氰酸盐，C(6)H(11)N(2) SCN，1-丁基-3-甲基咪唑鎓三氰基甲酸盐，C(8)H(15)N(2) C(4)N(3)，N-丁基-3-甲基吡啶鎓二氰胺盐，C(10)H(16)N C(2)N(3)，以及1-丁基-1-甲基吡咯烷鎓双[(三氟甲基)磺酰基]酰胺，C(9)H(20)N C(2)F(6)NO(4)S(2)。通过对残留物的场解吸和电喷雾电离质谱分析，排除了将其归为CA(+)离子的可能性，这一归类已通过精确质量测量得到证实，且因离子液体的热分解而存在错误归类。
