Abstract Distinguishing chemicals and improvement on analytical methods has a direct impact on modern chemical analysis. In this work, the dissociative ionization of xylene isomers was investigated using a femtosecond laser mass spectrometry (FLMS) method with a custom-built linear time-of-flight (TOF) instrument. Laser beams at 800 nm and 400 nm were used and intensity-dependent analysis of the obtained mass spectra was performed using principal component analysis (PCA) to distinguish the xylene isomers, which give identical mass spectra in appearance that cannot be distinguished using normal mass spectrometry methods. The results show that there is a statistically highly significant difference between the xylene isomers for two principal components (1 − α > 99.99%) and minimal information loss (<5%) took place during the PCA procedure. Also, the use of the k-medoid clustering method showed that the isomers may be distinguished in real-time for a wide range of ionization laser pulse powers with approximately 99% accuracy. The results suggest that real-time isomer analysis by the FLMS method is suitable for mass spectral identification applications. The FLMS method has been shown to be an important alternative to other mass spectrometric methods that use different ionization mechanisms.

中文翻译：

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使用飞秒激光质谱 (FLMS) 获得的光电离和解离质谱实时区分二甲苯异构体

摘要 化学物质的鉴别和分析方法的改进对现代化学分析有着直接的影响。在这项工作中，使用飞秒激光质谱 (FLMS) 方法和定制的线性飞行时间 (TOF) 仪器研究了二甲苯异构体的解离电离。使用 800 nm 和 400 nm 的激光束，并使用主成分分析 (PCA) 对所获得的质谱进行强度相关分析，以区分二甲苯异构体，其外观相同，无法使用普通质谱进行区分方法。结果表明，两种主要成分的二甲苯异构体之间存在统计学上非常显着的差异 (1 - α > 99.99%)，并且在 PCA 过程中发生的信息损失最小 (<5%)。此外，k-medoid 聚类方法的使用表明，可以以大约 99% 的准确度实时区分各种电离激光脉冲功率的异构体。结果表明，通过 FLMS 方法进行的实时异构体分析适用于质谱鉴定应用。FLMS 方法已被证明是其他使用不同电离机制的质谱方法的重要替代方法。