Preface

Finlayson-Pitts, B. J.; Pitts, James N.

doi:10.1016/b978-012257060-5/50000-9

Cited by 566 publications

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“…In wet atmospheric aerosols, nitric acid sticks readily to surfaces and displaces HCl, with replacement by HNO 3 . Sea salt particles of sodium chloride can be converted to sodium nitrate in this fashion [21]. Perhaps analogous processes occur during droplet production, desolvation, or ion extraction in ESI, especially when the ions pass through a long, narrow tube in a heated capillary extraction device.…”

Section: Comparison Of Ion Extraction Methodsmentioning

confidence: 99%

Tandem mass spectrometry of metal nitrate negative ions produced by electrospray ionization

Byers

Houk

2003

J. Am. Soc. Mass Spectrom.

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M(NO 3 ) xϪ ions are generated by electrospray ionization (ESI) of metal solutions in nitric acid in negative ion mode. Collision-induced reactions of these ions are monitored in a tandem mass spectrometer (MS) of quadrupole-octopole-quadrupole (QoQ) geometry. For Group 1and 2 elements, the M(NO 3 ) x Ϫ ions dissociate into NO 3 Ϫ and neutral metal nitrate molecules. These elements also form some M x (NO 3 ) xϩ1 Ϫ clusters, especially Li ϩ . Metal nitrate ions from transition elements and Group 13 elements fragment into oxo products and also undergo internal electron transfer to leave the M atom in a lower oxidation state. To calibrate the collision energy, the dissociation energy of O-NO 2 Ϫ is found to be 5.55 eV, about 0.76 eV lower than a value derived from thermochemistry. Most studies of small inorganic ions have been done in positive ion mode [14 -18]. Many metal-solvent clusters, e.g., M xϩ (H 2 O) n , n ϭ 1 to 6, are typically formed under "soft" ion extraction conditions [7,17,18]. Highly charged metal ions tend to react with solvent molecules to yield hydroxy or methoxy ions when energetic collision conditions are used to remove solvent during ion extraction. Preserving the original form of the metal ion in positive mode generally requires element-specific optimization of ion extraction conditions and leads to a variety of ion-solvent clusters.Previous work from our group [19] showed that an excess of nitric acid can be used to produce M(NO 3 ) x Ϫ ions in negative ion mode. A single set of ion extraction conditions yields these ions for many elements. This early work was done with only one stage of MS. The present work reports collision-induced dissociation (CID) reactions of these M(NO 3 ) x Ϫ ions in a triple "quadrupole" MS, actually a QoQ instrument. Experimental Samples and Sample PreparationConcentrated nitric acid was purchased from J. T. Baker (Phillipsburg, NJ) and used without further purification. Aliquots of the concentrated acid were mixed with HPLC grade methanol and deionized water (18 M⍀, Barnstead Nanopure, Newton, MA) to form a solvent of 0.05% nitric acid in 25% water:75% methanol. Aliquots of aqueous, acidic metal stock solutions (1000 ppm, Spex Certiprep, Metuchen, NJ ) were diluted with solvent to the desired concentrations.

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Section: Comparison Of Ion Extraction Methodsmentioning

confidence: 99%

Tandem mass spectrometry of metal nitrate negative ions produced by electrospray ionization

Byers

Houk

2003

J. Am. Soc. Mass Spectrom.

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“…Certain carbonyls are directly emitted by various sources, but the vast majority of them are produced in the atmosphere by oxidation of hydrocarbons. 13 Photolysis is an important removal pathway for atmospheric carbonyls. In the lower atmosphere, where the availability of radiation is limited to a wavelength of above B290 nm, the photolysis of carbonyls is driven by their weak absorption band in the wavelength range 240-360 nm as a result of a dipole forbidden n -p* transition.…”

Section: Introductionmentioning

confidence: 99%

“…In the lower atmosphere, where the availability of radiation is limited to a wavelength of above B290 nm, the photolysis of carbonyls is driven by their weak absorption band in the wavelength range 240-360 nm as a result of a dipole forbidden n -p* transition. 13,14 Photolysis of aldehydes, such as pentanal, is known to occur through the following pathways:…”

Section: Introductionmentioning

confidence: 99%

Photochemistry of aldehyde clusters: cross-molecular versus unimolecular reaction dynamics

Shemesh

Blair

Nizkorodov

et al. 2014

Phys. Chem. Chem. Phys.

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The unimolecular photochemistry of aldehydes has been extensively studied, both experimentally and computationally. However, less is known about the role of cross-molecular photochemical processes in the condensed-phase photolysis of aldehydes. The triplet-state photochemistry of pentanal in its pentameric (n = 5) cluster was investigated as a model for photochemical reactions of aliphatic aldehydes in atmospheric aerosols. This study employs ''on the fly'' dynamics simulations using a semi-empirical MRCI electronic code for the singlet and triplet states involved. Previous studies have shown that the triplet-state photochemistry of an isolated pentanal molecule is dominated by Norrish I and II reactions. The main findings for the cluster are: (1) 55% of the trajectories lead to a unimolecular or cross-molecular reaction within a timescale of 100 ps; (2) cross-molecular reactions occur in over 70% of the reactive trajectories; (3) the main cross-molecular processes involve an H-atom transfer from the CHO group of the excited pentanal to an O atom of a nearby pentanal; and (4) the unimolecular Norrish II reaction is suppressed by the cluster environment. The predictions are qualitatively supported by experimental results on the condensed-phase photolysis of an aliphatic aldehyde, undecanal. The computational approach should be useful for predicting the mechanisms of other condensed-phase organic photochemical reactions. These results demonstrate a major role of cross-molecular processes in the condensed-phase photolysis of carbonyls. The cross-molecular reactions discussed in this work are relevant to photolysis-driven processes in atmospheric organic aerosols. It is expected that the condensed-phase environment of an organic aerosol particle should support a multitude of similar cross-molecular photochemical processes.

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“…16 For example, for large (B10 mm) size particles, the falling droplet apparatus has been used extensively to study gas uptake and reaction. 1,3,13,17,18 FTIR studies of smaller particles have been carried out at relatively high particle concentrations; [19][20][21][22] following the particles with time using this method is complicated by continuously changing particle size distributions due to coagulation and settling of the particles.…”

Section: Introductionmentioning

confidence: 99%

“…[50][51][52][53][54][55]57,60,71,[81][82][83][84][85][86][87][88][89][90][91][92][93][94][95] SO 2 can also be oxidized in the gas phase, mainly by OH, 96 to produce sulfuric acid which is then taken up by cloud droplets and particles; however, this is generally a minor pathway compared to aqueous oxidation. 16 In this work, we demonstrate the application of DRIFTS to studying the uptake and oxidation of gaseous SO 2 at 50% relative humidity (RH) on NaCl-MgCl 2 Á 6H 2 O salt mixtures that have been previously reacted with OH formed by the photolysis of O 3 in the presence of water vapor. Because reaction (1) generates base, it is expected to increase the uptake of SO 2 as well as its oxidation by ozone which is particularly important above a pH of B 6.…”

Section: Introductionmentioning

confidence: 99%

A new approach to studying aqueous reactions using diffuse reflectance infrared Fourier transform spectrometry: application to the uptake and oxidation of SO2 on OH-processed model sea salt aerosol

Shaka

Robertson

Finlayson-Pitts

2007

Phys. Chem. Chem. Phys.

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A new approach to studying aqueous reactions using diffuse reflectance infrared Fourier transform spectrometry: application to the uptake and oxidation of SO2 on OH-processed model sea salt aerosol. Diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) is a powerful technique for analyzing solid powders and for following their reactions in real time. We demonstrate that it can also be applied to studying the uptake and reactions of gases in liquid films. Within the DRIFTS cell, a 10% (w/w) mixture of MgCl 2 Á 6H 2 O in NaCl was equilibrated with air at 50% RH, which is above the deliquescence point of the magnesium salt but below that of NaCl. This mixture of NaCl coated with an aqueous magnesium chloride solution was then reacted with gas phase OH to generate hydroxide ions via a previously identified interface reaction. This treatment, hereafter referred to as OH-processing, was sufficient to convert some of the magnesium chloride to Mg(OH) 2 and Mg 2 (OH) 3 Cl Á 4H 2 O, making the aqueous film basic and providing a reservoir of alkalinity. Subsequent addition of SO 2 to the basic processed mixture resulted in its uptake and conversion to sulfite which was measured by FTIR. The sulfite was simultaneously oxidized to sulfate by HOCl/OCl À that was formed in the initial OH-processing of the salt. Further uptake and oxidation of SO 2 in the aqueous film took place when the salt was subsequently exposed to O 3 . These studies demonstrate that DRIFTS can be used to study the chemistry in liquid films in real time, and are consistent with the hypothesis that the reaction of gaseous OH with chloride ions generates alkalinity that enhances the uptake and oxidation of SO 2 under these laboratory conditions.

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Preface

Cited by 566 publications

References 0 publications

Tandem mass spectrometry of metal nitrate negative ions produced by electrospray ionization

Tandem mass spectrometry of metal nitrate negative ions produced by electrospray ionization

Photochemistry of aldehyde clusters: cross-molecular versus unimolecular reaction dynamics

A new approach to studying aqueous reactions using diffuse reflectance infrared Fourier transform spectrometry: application to the uptake and oxidation of SO2 on OH-processed model sea salt aerosol

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