基于傅里叶变换离子回旋共振质谱仪(FT ICR MS)的超宽波段光解离光谱系统的研制及应用

Development and Application of a Ultra-wide-band Photodissociation Spectroscopy System Based on a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer

基于质谱技术的光解离光谱方法具有灵敏度高和可行性好的优势,近年来在气相离子化学和分析化学研究领域得到了快速发展和广泛应用。本工作基于一台7 T的傅里叶变换离子回旋共振质谱仪(FT ICR MS),搭建了超宽波段的可调谐激光光路系统,获得了气相离子超宽波段的光解离光谱。该系统的光谱可调谐范围为192~3 700 nm,是目前已知在单台质谱仪上可获得最宽波段的光解离光谱系统。超宽波段的波长覆盖范围使用两台宽波段可调谐OPO激光器实现,光路可以在真空传输,提高了紫外和红外激光的传输效率。该系统结合了电喷雾(ESI)电离源和FT ICR MS的高分辨能力以及超强的离子操控能力,可以获得目标离子的紫外-可见光以及中红外区域的光解离光谱,分别对应于分子的电子和振动能级,实现了分子结构信息的互补。以罗丹明110和色胺为例,获得了相应的离子在不同波段中的光解离光谱,初步证明了该仪器实现相关功能的可行性。

The method of photodissociation spectroscopy based on mass spectrometry was rapidly developed and widely applied in gas phase ionic chemistry and analytical chemistry due to its high sensitivity and feasibility in recent years. In this research, an optical system with ultra-wide-band tunable laser output was constructed and combined with a 7.0 T Fourier transfer ion cyclotron resonance mass spectrometer(FT ICR MS). The system could be used to acquire "Action" spectra of isolated ions. Compared with the traditional absorption spectroscopy, it had the advantage of high sensitivity, which could completely eliminate influence of impurities and solvents. After its generation, the target ion could be selected in FT ICR cell, and irradiated by laser with different wavelengths. The energy obtained after absorbing photons at appropriate wavelengths could cause the ions to dissociate and to form fragment ions to be detected. By gradually changing the wavelength of laser and analyzing the mass spectra under different wavelengths, the photodissociation spectra of target ions could be obtained through data analysis. The system applied here could be used to obtain ultra-wide-band photodissociation spectra of different ions in the gas phase. The full spectral tunable range of the system was 192-3 700 nm, which was, as far as we knew, the widest available tunable spectral range fulfilled on a single mass spectrometer. The ultra wide wavelength coverage was realized by two wavelength tunable OPO lasers. The optical path was set in vacuum, which improved the transmission efficiency of lasers in ultraviolet and infrared regions. The system combined the advantages of electrospray ionization(ESI), high mass resolution and superior ion handling capability of FT ICR MS. The UV-visible and mid-infrared photodissociation spectra of the target ion could be obtained, which were complementary, corresponding to their electronic and vibrational energy levels of molecules, respectively. Since the full spectrum for some target ion was generated under the same ion source, it avoided some unexpected spectral differences caused by ionization conditions and other instrument-relative factors. In this paper, rhodamine 110 and tryptamine were taken as examples. Photodissociation spectra of corresponding ions in different wavelength range were obtained, which preliminarily proved the feasibility of the method.