Dual-Polarity Ion Trap Mass Spectrometry: Dynamic Monitoring and Controlling Gas-phase Ion–Ion Reactions

A dual-polarity linear ion trap (LIT) mass spectrometer was developed in this study, and the method for simultaneously controlling and detecting cations and anions was proposed and realized in the LIT. With the application of an additional dipolar DC field on the ejection electrodes of an LIT, dual-polarity mass spectra could be obtained, which include both the mass-to-charge (m/z) ratio and charge polarity information of an ion. Compared with conventional method, the ion ejection and detection efficiency could also be improved by about one-fold. Furthermore, ion–ion reactions within the LIT could be dynamically controlled and monitored by manipulating the distributions of ions with opposite charge polarities. This method was then used to control and study the reaction kinetics of ion–ion reactions, including electron transfer dissociation (ETD) and charge inversion reactions. A dual-polarity collision-induced dissociation (CID) experiment was proposed and performed to enhance the sequence coverage of a peptide ion. Ion trajectory simulations were also carried out for concept validation and system optimization.

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Measurement of Ion Mobilities of Selected Amines by Ion Mobility Spectrometry

IlltIoduchontIonmobilityspectrometry(IMS)isagasphaseelectTophoreticandlyticaltechniqueinwhichionsatahaosphericpressureareallowedtodrift,separateandcollectbasedontheirdoferentmobilitiesinanelectricfield.ThequalitativeandquantitativeinformationoftheanalytescanbeacquiredfromthereducedmobilitiesandrelativeintensihesoftheirpeaksinIMSspectTa.IMSwasdevelopedtobeanewtecndqueinfieldapplications[1J.Thereducedmobility(Ko)iscalculatedaccordingtothefollowingequation:h=(L/Et)(P/7so)(2=s/nwhereListhed…     

Ion/Neutral,Ion/Electron,Ion/Photon,and Ion/Ion Interactions in Tandem Mass Spectrometry: Do We Need Them All? Are They Enough?

A range of strategies and tools have been developed to facilitate the determination of primary structures of analyte molecules of interest via tandem mass spectrometry (MS/MS). The two main factors that determine the primary structural information present in an MS/MS spectrum are the type of ion generated from the analyte molecule and the dissociation method. The ion type subjected to dissociation is determined by the ionization method/conditions and ion transformation processes that might take place after initial gas-phase ion formation. Furthermore, the range of analyte-related ion types can be expanded via derivatization reactions prior to mass spectrometry. Dissociation methods include those that simply alter the population of internal states of the mass-selected ion (i.e., activation methods like collision-induced dissociation) as well as processes that rely on the transformation of the ion type prior to dissociation (e.g., electron capture dissociation). A variety of ion interactions have been studied for the purpose of ion dissociation and ion transformation, including ion/neutral, ion/photon, ion/electron, and ion/ion interactions. A wide range of phenomena have been observed, many of which have been explored/developed as means for structural analysis. The techniques arising from these phenomena are discussed within the context of the elements of structural determination in tandem mass spectrometry: ion-type definition and dissociation. Unique aspects of the various ion interactions are emphasized along with any barriers to widespread implementation.     

Production of Superoxide Ion with Carbon Gas-Diffusion-Electrode And Reaction of Superoxide Ion with Aromatic Halide

Superoxide ion O~-_2 is prepared in aprotic media by carbon gas-diffusion-electrode for the first time. The experimental results indicate that this electrode is superior to carbon plane-electrode in the reaction of O~-_2 with p-bromonitrobenzene. When the gas-diffussion-electrode is used, the yield of the product nitrophenol increases by 20%, and the selectivity of the reaction is nearly doubled as compared with the plane-electrode.     

Synthetic Channel-forming Peptides and Ion Selectivity

Introduction PeptidesmadeupofalternatingL andD amino acidscanformβhelicesasingramicidinAorcyclic peptidesthataggregatetoformtubes[1].Inbothcases thestructuresarehollowwithallthesidechainspro jectingoutwards.Kennedyetal.[2]postulatedthat peptideshavingthe…     

Electronic Structure and Structure of Ion Pairs of Anionic σ Adducts of Polynitroarenes with Acetonate Ion

The anionic Yanovskii adducts of 1,3,5-trinitro- and 1,3-dinitrobenzenes, 1,3-dinitronaphthalene, and 3,5-dinitrobenzoic acid with sodium, potassium, and tetrabutylammonium acetonates in low-polarity solvents exist mostly as contact ion pairs, while in polar solvents, as solvent-separated ion pairs and free ions. Lowering the temperature increases the fraction of solvent-separated ion pairs in low-polarity solvents and of free ions in polar solvents, by shifting the equilibria to stronger solvated ionic species. By quantum-chemical calculations of the geometry and electronic structure of the anions and of the electronic absorption spectra of the free ions and ion pairs, as well as by a spectrophotometric study of adducts with solvents of various polarity it was established that the cation on ion-pair formation coordinates with the 4-nitro group with respect to the pyramidal node.     

Comparison of Functional Group Selective Ion–Molecule Reactions of Trimethyl Borate in Different Ion Trap Mass Spectrometers

We report here a comparison of the use of diagnostic ion–molecule reactions for the identification of oxygen-containing functional groups in Fourier-transform ion cyclotron resonance (FTICR) and linear quadrupole ion trap (LQIT) mass spectrometers. The ultimate goal of this research is to be able to identify functionalities in previously unknown analytes by using many different types of mass spectrometers. Previous work has focused on the reactions of various boron reagents with protonated oxygen-containing analytes in FTICR mass spectrometers. By using a LQIT modified to allow the introduction of neutral reagents into the helium buffer gas, this methodology has been successfully implemented to this type of an ion trap instrument. The products obtained from the reactions of trimethyl borate (TMB) with various protonated analytes are compared for the two instruments. Finally, the ability to integrate these reactions into LC-MS experiments on the LQIT is demonstrated.     

Aluminum Ion Removal from Monoaluminum Ovotransferrin by Pyrophosphate

Introduction The transferrins are a family of iron-binding proteins which are the requirement of a synergistic anion for the interaction of these proteins with metals.1,2 Although these proteins consist of a single chain of about 700 amino acid resides, they fold into two distinct, homolo-gous lobes connected by a short polypeptide.2-4 Each lobe contains one high-affinity iron-binding site, which is designated as the C-terminal or the N-terminal site, respectively. The ligands for each iron-b…     

Machine Learning towards Screening Solid-state Lithium Ion Conductors

Machine learning is an emerging method to discover new materials with specific characteristics.An unsupervised machine learning research is highlighted to discover new potential lithium ionic conductors by screening and clustering lithium compounds,providing inspirations for the development of solid-state electrolytes and practical batteries.     

Ion pair receptors based on anion-π interaction

A novel type of ditopic ion pair receptors based on anion-π interaction is reported. Oxacalix[2]arene[2]triazine azacrowns were synthesized efficiently from a one-pot reaction between 2,4-dichloro-4-methoxytriazine and 3,5-dihydroxybenzaldehyde followed by condensation with a diamine and reduction of bisimine; they acted as selective ditopic receptors to recognize ion pairs.     

Stydy on the Model of Ion Exchange Kinetics

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Ion mobility spectrometry in scientific literature and in the International Journal for Ion Mobility Spectrometry (1998–2007)

Starting in 1998 the International Society for Ion Mobility Spectrometry, organising the annual conferences on ion mobility spectrometry, began to issue the International Journal for Ion Mobility Spectrometry. Now, in the 11th year the journal will be the first year together with SPRINGER. Therefore, the article focusses on the history of IMS providing an up to date account based on a systemetic search using the Web-of-Science and SciFinder search engines.     

Studies on Electrophilic Substitution of Quasi-Aromatic Metal Ion Complexes

The electrophilic substitution reaction occurring to the chelate ring of the complexes could be regarded as an indication of quasi-aromaticity of the ring systems, no catalyst was used and only triethylamine was employed, implying that the aroylating agents with different p-substituents are polarized enough to be effective electrophiles to attack the methine carbon of the electron-rich substrate 1. This property is probably the clue to polarization of the ligand electrons by the nickel( Ⅱ ) ion and to the participation of the nickel( Ⅱ ) in the π-bond systems of the two coordinated conjugated rings. The linearity relationship between vd-d maxima, E1/2OX(1) and σp are obtained, respectively. The electronic environment of central metal ion as well as the aromaticity of the ring system are affected by the electronic properties of the p-substituents. A comparison of the electrochemical results with each other showed .that when the electronegativity of the substituent was higher, the oxidation(Ni2+/Ni3+)     

Ion transfer across the immiscible water—o-nitrotoluene interface

The standard Gibbs energies of transfer of some ions across the immiscible water—o-nitrotoluene interface have been determined voltammetrically. These values are compared with the theoretical values calculated using a model of ionic solvation.     

Catalytic Kinetic Spectrophotometric Method for Determination of Phosphate Ion

The kinetic method for the determination of phosphate microamounts was described. The developed method is based on catalytic effect of phosphate on sodium pyrogallol-5-sulphonate （PS） by dissolved oxygen. The reaction was followed spectrophotometrically by measuring the rate of change in the values of the absorbance of the oxidation product at 437 nm. The optimum reaction conditions are PS （0.44×10^-3 mol·L^-1） and HClO4 （3.6×10^-6 mol·L^-1） at 25 ℃. Following this procedure, phosphate can be determined with a linear calibration graph up to 0.23 μg·mL^-1. The interference effect of several species was also investigated and it was found that the most common cations and anions did not interfere with the determination. The developed procedure was successfully applied to the determination of phosphate in natural waters and soil.     

Magnesium Ion Selective Electrodes Based on β-Diketone Compounds

Abstract

The ion selectivities for poly(vinyl chloride) (PVC)-matrix membrane ion-selective electrodes based on seven lipophilic diketone compounds were examined. All the electrodes based on the tested five β-diketone cómpounds exhibited clear Mg²′-selectivity under high pH conditions (pH10). Especially, the electrode based on 2-acetyl-1-tetralone shows excellent Mg²⁺-selectivity, and the selectivity coefficients of the Mg²+ -electrode to Ca²+, K⁺ and K⁺ (log K^pot _{mg, ca} log K^pol _mg.k and log K^pot _Mg.Na) in pH 10 solution were ?2.2, ?1.9 and ?2.7, respectively. This elecrode gave a response slope of about 60 mV/pMg²⁺ ranging from 1 × 10^?2 to 2 × 10^?2, which corresponds to twice the usual Nernstian theoretical responce slope for the divalent cation. This phenomenon is advantageous for the acccurate determination of Mg²⁺.     

Studies on Inorganic Ion Exchanger Containing Phosphorus(IX)——Kinetics of Ion Exchange Reaction for Alkaline Earths on SVPP

A shell reaction mechanism and its mathematic model were used to inquire into the kinetics of ion exchange reaction between alkaline earth metal ions and H- form of micro-crystalline SVPP.The activation energy ( Ea ), entropy of activation ( ΔS) and self-diffusion coefficient ( Do ) of alkaline earths were calculated bysolving the Nernst-Planck equations on a IBM-PC computer. The linear relations between the bare ionic radii of alkaline earths ro andEa, ΔSor lgDo have been obtained.     

Gold Ion–Angiotensin Peptide Interaction by Mass Spectrometry

Stimulated by the interest in developing gold compounds for treating cancer, gold ion–angiotensin peptide interactions are investigated by mass spectrometry. Under the experimental conditions used, the majority of gold ion–angiotensin peptide complexes contain gold in the oxidation states I and III. Both ESI-MS and MALDI-TOF MS detect singly/multiply charged ions for mononuclear/multinuclear gold-attached peptides, which are represented as [peptide + a Au(I) + b Au(III) + (e - a -3b) H]^e+, where a,b ≥ 0 and e is charge. ESI-MS data shows singly/multiply charged ions of Au(I)-peptide and Au(III)-peptide complexes. This study reveals that MALDI-TOF MS mainly detects singly charged Au(I)-peptide complexes, presumably due to the ionization process. The electrons in the MALDI plume seem to efficiently reduce Au(III) to Au(I). MALDI also tends to enhance the higher polymeric forms of gold-peptide complexes regardless of the laser power used. Collision-induced dissociation experiments of the mononuclear and dinuclear gold-attached peptide ions for angiotensin peptides show that the gold ion (a soft acid) binding sites are in the vicinity of Cys (a soft ligand), His (a major anchor of peptide for metal ion chelation), and the basic residue Arg. Data also suggests that the abundance of gold-attached peptides increases with higher gold concentration until saturation, after which an increase in gold ion concentration leads to the aggregation and/or precipitation of gold-bound peptides.     

Sorption of Molecular Oxygen by Metal–Ion Exchanger Nanocomposites

Kinetic features are studied of the chemisorption and reduction of molecular oxygen from water by metal–ion exchanger nanocomposites that differ in the nature of the dispersed metal and state of oxidation. In the Pd < Ag < Cu series, the increasing chemical activity of metal nanoparticles raises the degree of oxygen sorption due to its chemisorption and subsequent reduction, while the role of the molecular chemisorption stage increases in the Cu < Ag < Pd series. Metal particles or their oxides are shown to act as adsorption sites on the surface and in the pores of the ion-exchanger matrix; the equilibrium sorption coefficient for oxygen dissolved in water ranges from 20 to 50, depending on the nature and oxidation state of the metal component.