Direct observation of polymerization in the oleic acid–ozone heterogeneous reaction system by photoelectron resonance capture ionization aerosol mass spectrometry
Direct observation of polymerization in the oleic acid–ozone heterogeneous reaction system by photoelectron resonance capture ionization aerosol mass spectrometry
复制标题
光电子共振捕获电离气溶胶质谱直接观察油酸-臭氧非均相反应体系中的聚合反应
DOI：
10.1016/j.atmosenv.2005.10.065
复制
发表时间：
2006
影响因子：
5
通讯作者：
G. Petrucci
中科院分区：
文献类型：
--
作者：
J. Zahardis;B. LaFranchi;G. Petrucci
通过光电子共振捕获电离 (PERCI) 质谱 (MS) 研究了颗粒相 9-十八碳烯酸（油酸）臭氧分解反应的高分子量产物。油酸颗粒（dg=202nm，σg=1.97）在流动反应器中与臭氧（1.8×10−4atm）反应，反应时间分别为8秒和23秒。使用差动泵送颗粒入口在线对颗粒进行采样，并通过 PERCI-MS 进行化学分析。 PERCI 是一种软电离方法，可以直接测量相对高分子量的化合物，从而促进分子识别。除了先前报道的环状含氧化合物（例如二次臭氧化物和偕二过氧化物）之外，我们还证明了颗粒表面聚合物的形成。建议通过将 Criegee 中间体添加到油酸中形成 α-酰氧基烷基氢过氧化物，然后将 Criegee 中间体添加到该初始加成产物和后续产物中来进行聚合物形成。最终，通过这些α-酰氧基烷基氢过氧化物中间体的脱水形成聚酐。最高分子量的未片段化聚酸酐经测量为 963U，是通过将四种 Criegee 中间体连续添加到母体油酸分子中而产生的。这些产品的低挥发性，加上它们的高极性，可能会改变颗粒相的吸湿性，从而增强这些颗粒的云凝结特性。此外，颗粒表面形成的聚合物产物可能会显着改变反应气体的扩散，从而影响大气微量气体的反应吸收并影响大气的氧化能力。
High molecular weight products of the ozonolysis reaction of particle-phase 9-octadecenoic acid (oleic acid) have been studied by photoelectron resonance capture ionization (PERCI) mass spectrometry (MS). Oleic acid particles (dg=202nm, σg=1.97) were reacted with ozone (1.8×10−4atm) in a flow reactor at reaction times of 8 and 23s. Particles were sampled on-line with a differentially pumped particle inlet and chemically analyzed by PERCI-MS. PERCI is a soft ionization method that permits the direct measurement of relatively high molecular weight compounds, facilitating molecular identification. In addition to cyclic oxygenates, such as secondary ozonides and geminal diperoxides that were reported previously, we demonstrate the formation of polymers at the particle surface. Polymer formation is proposed to proceed via addition of a Criegee intermediate to oleic acid forming an α-acyloxyalkyl hydroperoxide, and subsequent additions of Criegee intermediates to this initial addition product and later generations. Ultimately, polyanhydrides are formed through dehydration of these α-acyloxyalkyl hydroperoxide intermediates. The highest molecular weight, unfragmented polyanhydride has been measured at 963U, resulting from the successive addition of four Criegee intermediates to a parent oleic acid molecule. The low volatility of these products, coupled with their high polarity, may alter particle phase hygroscopicity that can enhance the cloud condensation properties of these particles. Further, the polymer products formed at the particles’ surface may significantly alter diffusion of reactive gases, thereby affecting the reactive uptake of atmospheric trace gases and impacting the oxidizing capacity of the atmosphere.