Doroshenko V M, Cotter R J
Middle Atlantic Mass Spectrometry Laboratory, Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
J Mass Spectrom. 1998 Apr;33(4):305-18. doi: 10.1002/(SICI)1096-9888(199804)33:4<305::AID-JMS635>3.0.CO;2-9.
A matrix-assisted laser desorption/ionization-quadrupole ion trap/reflectron time-of-flight (MALDI-QIT/reTOF) mass spectrometer design and its operation in both normal and tandem mass spectrometric modes are described. A parabolic reflectron was found to be capable of providing mass resolution of 5000 for an initial ion energy distribution ranging over a 50% energy interval of the entire reflectron energy range. The sensitivity, ion isolation and fragmentation efficiency in the MALDI-QIT/reTOF instrument were close to those observed in the MALDI/QIT mass spectrometer. The mass resolution was shown to depend on the extraction field potentials, the r.f. trapping voltage amplitude and the phase of shutting down the r.f. voltage before extraction. At values of qs < 0.3-0.4 the mass resolution does not depend on the ion mass, is in a range of 1000-1400 and is governed by the extraction voltages and the ion temperature before extraction, the latter shown to be in the range 1180-1690 K. The variation of the mass resolution for ions at values of qs > 0.4 is irregular but normally it is lower than that for ions having lower qs values. Mass spectral line positions shifted when the trapping voltage before extraction was varied. The line shifts were larger for lower mass ions and were comparable to the line widths in the case of very low masses.
本文描述了一种基质辅助激光解吸/电离-四极杆离子阱/反射式飞行时间（MALDI-QIT/reTOF）质谱仪的设计及其在正常和串联质谱模式下的运行情况。研究发现，对于初始离子能量分布在整个反射器能量范围的50%能量区间内的情况，抛物线反射器能够提供5000的质量分辨率。MALDI-QIT/reTOF仪器的灵敏度、离子分离和碎裂效率与MALDI/QIT质谱仪中观察到的相近。结果表明，质量分辨率取决于提取场电位、射频阱电压幅度以及提取前关闭射频电压的相位。当qs < 0.3 - 0.4时，质量分辨率与离子质量无关，在1000 - 1400范围内，且由提取电压和提取前的离子温度决定，后者显示在1180 - 1690 K范围内。对于qs > 0.4的离子，质量分辨率的变化不规则，但通常低于qs值较低的离子。当提取前的阱电压变化时，质谱线位置会发生偏移。对于较低质量的离子，线偏移较大，对于非常低质量的离子，线偏移与线宽相当。
