Hyphenation of fast gas chromatography to photo-ionisation mass spectrometry for comprehensive analysis of climate and health-relevant organic aerosol components from dynamic combustion processes

众所周知，有机气溶胶的成分对人类健康和气候有复杂的影响。研究燃烧过程的动态变化，如原木燃烧或内燃机在不同负荷下的动态变化，需要具有适当时间分辨率的测量技术来跟踪复杂有机排放的定性和定量变化。作为软电离技术的单光子(SPI)和共振增强多光子电离(REMPI)与飞行时间质谱仪(TOFMS)相结合，满足了这些要求。然而，仅仅基于分子质量，不能对化合物进行明确的鉴定。SPI/REMPI-TOFMS采用新型Peltier调节剂的快速气相色谱联用可以克服这一问题，分离同量异构体，而保留时间相同但分子质量不同的化合物在质谱图上会被不同的峰分开。因此，可以在动态燃烧过程中以足够的时间分辨率分析单个挥发性化合物到半挥发性化合物。重点将放在烷基化多环芳烃(PAH)和酚类物种上，它们都可以用SPI-和REMPI-TOFMS进行分析，检测下限较低。烷基化多环芳烃主要是由化石燃料燃烧过程中排放的，最近已经走向多环芳烃研究的中心阶段，因为已经证明它们可以表现出与其不可替代的基本结构显著不同的毒理学性质。已知酚类物质主要是由生物质燃烧排放的，并被讨论为减轻燃烧气溶胶的其他化合物的毒理效应。除了排放的毒理学评估外，这些数据对于预测环境空气中可能的转化过程也很有价值，例如臭氧形成潜力或二次有机气溶胶的形成。最后，可以进一步利用Fast-GC-SPI/REMPI设置与热光碳分析仪的附加联用，以研究颗粒结合的有机物种，涵盖有机气溶胶排放的全部挥发性范围。

Components of organic aerosol are known to have complex impacts on human health and climate. The investigation of dynamic changes in combustion processes, such as in log wood combustion or internal combustion engines at different loads, requires measurement techniques of appropriate time resolution to follow qualitative and quantitative changes of complex organic emissions. Single-photon (SPI) and resonance-enhanced multi-photon ionisation (REMPI) as soft ionisation techniques combined with time-of-flight mass spectrometry (TOFMS) fulfil these requirements. However, solely based on molecular mass no definite identifications of compounds can be carried out. The hyphenation of fast gas chromatography with a novel Peltier-modulator to SPI/REMPI-TOFMS can overcome this issue and separate isobaric species, while compounds of equal retention time but different molecular mass are separated by different peaks in the mass spectra. Hence, single volatile to semi-volatile compounds can be analysed with sufficient time resolution during dynamic combustion processes. The focus will be on alkylated polycyclic aromatic hydrocarbons (PAH) and phenolic species, which both can be analysed by SPI- and REMPI-TOFMS with low limits of detection. Alkylated PAHs, which are mainly emitted by combustion processes using fossil fuels, have recently moved towards the centre stage of PAH research, because it has been shown that they can exhibit significantly different toxicological properties than their unsubstituted basic structures. Phenolic species are known to be emitted by mainly biomass combustion and are discussed as mitigating toxicological effects of other compounds of the combustion aerosol. In addition to the toxicological assessment of emissions, the data can be valuable to predict possible conversion processes in ambient air, e.g. ozone formation potential or the formation of secondary organic aerosol. Finally, the Fast-GC-SPI/REMPI setup can be further utilised in an additional hyphenation to a thermal-optical carbon analyser to investigate particle-bound organic species , covering the full volatility range of organic aerosol emission.