Probing Interfacial Chemistry of Single Droplets with Field-Induced Droplet Ionization Mass Spectrometry: Physical Adsorption of Polycyclic Aromatic Hydrocarbons and Ozonolysis of Oleic Acid and Relat

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• 作者：Ronald L. Grimm ; Robert Hodyss ; and J. L. Beauchamp
• 刊名：Analytical Chemistry
• 出版年：2006
• 出版时间：June 1, 2006
• 年：2006
• 卷：78
• 期：11
• 页码：3800 - 3806
• 全文大小：214K
• 年卷期：v.78,no.11(June 1, 2006)
• ISSN：1520-6882

文摘

The recently developed technique of field-induced dropletionization (FIDI) is applied to study interfacial chemistryof a single droplet. In a new variation of the FIDI method,1-2-mm-diameter droplets hang from a capillary andundergo heterogeneous reactions between solution-phaseanalytes and gas-phase species. Following a specifiedreaction time, the application of a high electric fieldinduces FIDI in the droplet, generating fine jets of highlycharged progeny droplets that are characterized by massspectrometry. Sampling over a range of delay timesfollowing exposure of the droplet to gas-phase reactants,the spectra yield the temporal variation of reactant andproduct concentrations. We illustrate the technique withthree examples: the adsorption of the polycyclic aromatichydrocarbon naphthalene into a water-methanol droplet,the ozonolysis of oleic acid, and localization of thecarbon-carbon double bond within a lysophosphatidicacid. Gas-phase naphthalene reacts with 80% methanol-20% water droplets containing 100 M silver nitrate.Positive ion mass spectra show increasing concentrationsof silver ion-naphthalene adducts as exposure timesincrease. To examine the ozonolysis of organic molecules,gas-phase ozone generated by a mercury pencil-style lampreacts with either 10 M oleic acid or 100 M oleoyl-L--lysophosphatidic acid (LPA; 18:1). Negative ion spectrafrom the ozonolysis of oleic acid show azelaic acid and9-oxononanoic acid as the principle reaction products.Ozonolysis products from LPA (18:1) unambiguouslydemonstrate the double bond position in the originalphosopholipid.