Rados Edita, Pittenauer Ernst, Frank Johannes, Varmuza Kurt, Allmaier Günter
Institute of Chemical Technologies and Analytics, TU Wien (Vienna University of Technology), Vienna, Austria.
Joint Workshop of the Faculty of Technical Chemistry, TU Wien (Vienna University of Technology), Vienna, Austria.
Rapid Commun Mass Spectrom. 2018 Apr 30;32(8):649-656. doi: 10.1002/rcm.8075.
We have developed a target system which enables the use of only one target (i.e. target preparation set) for three different laser desorption ionization (LDI)/matrix-assisted laser desorption ionization (MALDI) mass spectrometric instruments. The focus was on analysing small biomolecules with LDI for future use of the system for the study of meteorite samples (carbonaceous chondrites) using devices with different mass spectrometric performance characteristics.
Three compounds were selected due to their potential presence in meteoritic chondrites: tryptophan, 2-deoxy-d-ribose and triphenylene. They were prepared (with and without MALDI matrix, i.e. MALDI and LDI) and analysed with three different mass spectrometers (LinTOF/curved field RTOF, LinTOF/RTOF and QqRTOF). The ion sources of two of the instruments were run at high vacuum, and one at intermediate pressure. Two devices used a laser wavelength of 355 nm and one a wavelength of 337 nm.
The developed target system operated smoothly with all devices. Tryptophan, 2-deoxy-d-ribose and triphenylene showed similar desorption/ionization behaviour for all instruments using the LDI mode. Interestingly, protonated tryptophan could be observed only with the LinTOF/curved field RTOF device in LDI and MALDI mode, while sodiated molecules were observed with all three instruments (in both ion modes). Deprotonated tryptophan was almost completely obscured by matrix ions in the MALDI mode whereas LDI yielded abundant deprotonated molecules.
The presented target system allowed successful analyses of the three compounds using instruments from different vendors with only one preparation showing different analyser performance characteristics. The elemental composition with the QqRTOF analyser and the high-energy 20 keV collision-induced dissociation fragmentation will be important in identifying unknown compounds in chondrites.
我们开发了一种靶标系统，该系统能够仅使用一个靶标（即靶标制备装置）用于三种不同的激光解吸电离（LDI）/基质辅助激光解吸电离（MALDI）质谱仪。重点在于使用LDI分析小生物分子，以便未来利用该系统，通过具有不同质谱性能特征的设备研究陨石样本（碳质球粒陨石）。
由于这三种化合物可能存在于陨石球粒中，因此选择了色氨酸、2-脱氧-D-核糖和三亚苯。对它们进行了制备（添加和不添加MALDI基质，即MALDI和LDI），并使用三种不同的质谱仪（线性飞行时间/弯曲场反射式飞行时间质谱仪、线性飞行时间/反射式飞行时间质谱仪和四极杆-线性离子阱-反射式飞行时间质谱仪）进行分析。其中两台仪器的离子源在高真空下运行，一台在中压下运行。两台设备使用355nm的激光波长，一台使用337nm的波长。
所开发的靶标系统在所有设备上均能平稳运行。在使用LDI模式时，色氨酸、2-脱氧-D-核糖和三亚苯在所有仪器上均表现出相似的解吸/电离行为。有趣的是，仅在LDI和MALDI模式下，使用线性飞行时间/弯曲场反射式飞行时间质谱仪才能观察到质子化色氨酸，而在所有三台仪器上（两种离子模式下）均能观察到钠化分子。在MALDI模式下，去质子化色氨酸几乎完全被基质离子掩盖，而LDI则产生了大量的去质子化分子。
所展示的靶标系统仅通过一次制备，就能够使用来自不同供应商的仪器成功分析这三种化合物，这些仪器具有不同的分析器性能特征。使用四极杆-线性离子阱-反射式飞行时间质谱仪分析器的元素组成以及高能20keV碰撞诱导解离碎片分析，对于鉴定球粒陨石中的未知化合物将具有重要意义。
