Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
J Am Soc Mass Spectrom. 2020 Jan 2;31(1):117-123. doi: 10.1021/jasms.9b00019. Epub 2019 Nov 20.
MeV-SIMS is an emerging mass spectrometry imaging method that employs fast, heavy ions to desorb secondary molecules from the analyzed sample. High yields and low fragmentation rates of large molecules, associated with the dominating electronic sputtering process, make it particularly useful in biomedical research, where insight into the distribution of organic molecules is vital. Both yield and fragmentation of desorbed molecules in MeV-SIMS rely on characteristics of the primary ion but may also be impaired by poor instrumental settings. After utilizing secondary ion optics in the linear mass spectrometer at the micro-analytical center of the Jožef Stefan Institute, we demonstrate very efficient detection of secondary ions. As a result, the secondary ion yield, using such settings, solely depends on the species and the characteristics of the primary ion. In order to analyze the yield dependence on the primary ion energy, and the corresponding stopping power within the electronic excitation regime, we used a continuous electron multiplier detector to measure the primary ion current during each measurement of the mass spectra. Secondary ion yield as a function of the primary ion energy and charge is presented as well as fragmentation rates of organic molecules arginine and leu-enkephalin. Other influential instrumental drawbacks are also studied, and their effect on the results is discussed.
MeV-SIMS 是一种新兴的质谱成像方法，它采用高速重离子从被分析样品中解吸次级分子。大分子的高产率和低碎片化率与占主导地位的电子溅射过程相关，这使得它在生物医学研究中特别有用，因为深入了解有机分子的分布至关重要。MeV-SIMS 中解吸分子的产率和碎片化既依赖于初级离子的特性，也可能受到仪器设置不佳的影响。在利用乔斯法斯特研究所微分析中心线性质谱仪中的二次离子光学器件之后，我们展示了非常高效的二次离子检测。因此，在这种设置下，二次离子产率仅取决于初级离子的种类和特性。为了分析初级离子能量对产率的依赖性以及电子激发范围内的相应阻止能力，我们使用连续电子倍增器探测器在每次测量质谱时测量初级离子电流。还展示了次级离子产率随初级离子能量和电荷的变化以及有机分子精氨酸和亮氨酸脑啡肽的碎片化率。还研究了其他有影响的仪器缺陷，并讨论了它们对结果的影响。
