Australian Centre for Research on Separation Science (ACROSS), School of Natural Sciences, University of Tasmania, GPO Box 252-75, Hobart, Tasmania 7001, Australia.
Institute for Marine and Antarctic Studies (IMAS), Private Bag 129, University of Tasmania, Hobart, Tasmania 7001, Australia.
J Chromatogr A. 2020 Jan 11;1610:460557. doi: 10.1016/j.chroma.2019.460557. Epub 2019 Sep 20.
Biomass burning (BB) emissions are a significant source of particles to the atmosphere, especially in the Southern Hemisphere, where the occurrence of anthropogenic and natural wild fires is common. These emissions can threaten human health through increased exposure, whilst simultaneously representing a significant source of trace metals and nutrients to the ocean. One well known method to track BB emissions is through monitoring the atmospheric concentration of specific monosaccharide anhydrides (MAs), specifically levoglucosan and its isomers, mannosan and galactosan. Herein, a new method for the determination of levoglucosan and its isomers in marine and terrestrial aerosol samples is presented, which delivers both high selectivity and sensitivity, through the coupling of ion chromatography and triple quadrupole tandem mass spectrometry. Optimal chromatographic conditions, providing baseline separation for target anhydrosugars in under 8 min, were obtained using a Dionex CarboPac PA-1 column with an electrolytically generated KOH gradient. To improve the ionisation efficiency for MS detection, an organic make-up solvent was fed into the IC column effluent before the ESI source, and to further increase both sensitivity and selectivity, cationisation of levoglucosan was investigated by adding salts into the make-up solvent, namely, sodium, ammonium and lithium salts. Using positive lithium cationisation with 0.5 mM lithium chloride in methanol as the make-up solvent, delivered at a flow rate of 0.02 mL min, the levoglucosan response was improved by factors of 100 and 10, comparing to negative ionisation and positive sodium cationisation, respectively. Detection was carried out in SRM mode for quantitation and identification, achieving an instrumental LOD of 0.10, 0.12 and 0.5 µg L for levoglucosan, mannosan and galactosan, respectively. Finally, the method was applied to the analysis of 41 marine and terrestrial aerosol samples from Australia, its surrounding coastal waters and areas within the remote Southern Ocean, covering a large range of BB marker concentrations.
生物质燃烧 (BB) 排放是大气中颗粒物的重要来源，尤其是在南半球，那里经常发生人为和自然野火。这些排放物会通过增加暴露而威胁人类健康，同时也是海洋中痕量金属和营养物质的重要来源。一种众所周知的跟踪 BB 排放的方法是监测大气中特定单糖酐 (MA) 的浓度，特别是左旋葡聚糖及其异构体甘露聚糖和半乳糖。本文介绍了一种新的方法，用于测定海洋和陆地气溶胶样品中的左旋葡聚糖及其异构体，该方法通过离子色谱和三重四极杆串联质谱的耦合，实现了高选择性和高灵敏度。通过 Dionex CarboPac PA-1 柱和电解生成的 KOH 梯度，在不到 8 分钟的时间内即可实现目标脱水糖的基线分离，从而获得最佳的色谱条件。为了提高 MS 检测的离子化效率，在将 IC 柱流出物引入 ESI 源之前，将有机基质溶剂泵入 IC 柱，为了进一步提高灵敏度和选择性，研究了向基质溶剂中添加盐（即，钠盐、铵盐和锂盐）对左旋葡聚糖的阳离子化作用。使用正锂阳离子化，以甲醇中的 0.5mM 氯化锂作为基质溶剂，流速为 0.02mL min，与负离子化和正钠离子化相比，左旋葡聚糖的响应分别提高了 100 倍和 10 倍。采用 SRM 模式进行定量和鉴定检测，左旋葡聚糖、甘露聚糖和半乳糖的仪器检出限分别为 0.10、0.12 和 0.5μg L。最后，该方法应用于分析来自澳大利亚及其周围沿海水域和偏远南大洋地区的 41 个海洋和陆地气溶胶样品，涵盖了广泛的 BB 标记物浓度范围。
