Hampton Christina Y, Silvestri Catherine J, Forbes Thomas P, Varady Mark J, Meacham J Mark, Fedorov Andrei G, Degertekin F Levent, Fernández Facundo M
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA.
J Am Soc Mass Spectrom. 2008 Sep;19(9):1320-9. doi: 10.1016/j.jasms.2008.06.012. Epub 2008 Jun 28.
The internal energy deposition of a Venturi-assisted array of micromachined ultrasonic electrosprays (AMUSE), with and without the application of a DC charging potential, is compared with equivalent experiments for Venturi-assisted electrospray ionization (ESI) using the "survival yield" method on a series of para-substituted benzylpyridinium salts. Under conditions previously shown to provide maximum ion yields for standard compounds, the observed mean internal energies were nearly identical (1.93-2.01 eV). Operation of AMUSE without nitrogen flow to sustain the air amplifier focusing effect generated energetically colder ions with mean internal energies that were up to 39% lower than those for ESI. A balance between improved ion transfer, adequate desolvation, and favorable ion energetics was achieved by selection of optimum operational ranges for the parameters that most strongly influence the ion population: the air amplifier gas flow rate and API capillary temperature. Examination of the energy landscapes obtained for combinations of these parameters showed that a low internal energy region (<or=1.0 eV) was present at nitrogen flow rates between 2 and 4 L min(-1) and capillary temperatures up to 250 degrees C using ESI (9% of all parameter combinations tested). Using AMUSE, this region was present at nitrogen flow rates up to 2.5 L min(-1) and all capillary temperatures (13% of combinations tested). The signal-to-noise (S/N) ratio of the intact p-methylbenzylpyridinium ion obtained from a 5 microM mixture of thermometer compounds using AMUSE at the extremes of the studied temperature range was at least fivefold higher than that of ESI, demonstrating the potential of AMUSE ionization as a soft method for the characterization of labile species by mass spectrometry.
采用“存活产率”方法，在一系列对位取代苄基吡啶鎓盐上，对有无直流充电电位的文丘里辅助微机械超声电喷雾阵列（AMUSE）的内能沉积与文丘里辅助电喷雾电离（ESI）的等效实验进行了比较。在先前已证明能为标准化合物提供最大离子产率的条件下，观察到的平均内能几乎相同（1.93 - 2.01电子伏特）。在没有氮气流以维持空气放大器聚焦效应的情况下运行AMUSE，会产生能量更低的离子，其平均内能比ESI产生的离子低达39%。通过为对离子群体影响最大的参数选择最佳操作范围，即空气放大器气体流速和API毛细管温度，实现了改进的离子转移、充分的去溶剂化和有利的离子能量学之间的平衡。对这些参数组合获得的能量分布图的研究表明，使用ESI时，在氮气流速为2至4 L min⁻¹且毛细管温度高达250℃的情况下，存在一个低内能区域（≤1.0电子伏特）（在所测试的所有参数组合中占9%）。使用AMUSE时，该区域出现在氮气流速高达2.5 L min⁻¹且所有毛细管温度的情况下（在所测试的组合中占13%）。在研究温度范围的极端条件下，使用AMUSE从5 microM温度计化合物混合物中获得的完整对甲基苄基吡啶鎓离子的信噪比（S/N）至少比ESI高五倍，这证明了AMUSE电离作为一种通过质谱表征不稳定物种的软方法的潜力。
