Theoretical Study on the Mass Transfer of Metal Ions in Ion Exchange Process

The kinetics of ion exchange between Ca2 , Mg2 , Co(Ⅱ), Cu(Ⅱ),Ni(Ⅱ), Fe(Ⅲ), y3 or Sm3 , respectively, in 0.50 mol/L HC1 and H on macrorecticular sulfonic ion exchange resin and the kinetics of the same reactions (M -H exchange) when Mn(Ⅱ) coexisted in resin phase as accelerating ion were studied. The accelerating effect manifested and its rule are consistent with the accelerating effect theory based on the concept concerned with adsorption electrical double layer which has been suggested in a previous paper published.     

“True” Concentration Determination Using a Concentration and Composition Sensitive Infrared Detector for Molecular Weight Characterization of Polyolefins

Summary: The infrared detector with a composition channel provides the ability to construct “true” concentration of the polyethylene-polypropylene copolymer and polymer blends to compensate the different infrared responses to each component. Using this “true” concentration constructed by the infrared detector, triple detector gel permeation chromatography (GPC) could generate conventional (by column calibration) and absolute (by laser light scattering) molecular weight and molecular weight distribution data comparable to data obtained by using the concentration obtained by a differential reflex index concentration detector. In addition to its unique feature of in-situ composition detection, the infrared detector in its mass detection mode possesses the advantages of faster equilibrium time, more stable baseline, less effect from temperature variation, and low sensitivity to moisture or air in the solvent.     

Reconstructed Mass Spectra,A Novel Approach for the Utilization of Gas Chromatograph—Mass Spectrometer Data

Abstract

Peak profile analysis of each of the few hundred mass chromatograms generated during a complete GC-MS experiment identifies all m/e values which maximize at any of the few hundred consecutive mass spectra recorded during the gas chromatogram. The resulting sets of data correspond to the mass spectrum of each eluting component (even very minor ones) practically free of the contributions of unresolved companion substances, tailing fractions, column bleed, etc. These “reconstructed mass spectra” are therefore more easily interpreted or automatically identified than the mass spectra originally recorded. A plot of the summed abundance of the ions that maximize at a given spectrum index number (“mass resolved gas chromatogram”) results in a gas chromatogram of dramatically improved apparent resolution.     

Gas-Phase Fragmentation Studies of Biotinylated,Hexaethylene Glycol–Spacered Oligosaccharides—Molecular Probes—Using Electrospray Mass Spectrometry on a Hybrid High-Resolution Mass Spectrometer

The electrospray ionization high-resolution mass spectra of biotinylated hexaethylene glycol–spacered molecular probes bearing biologically relevant carbohydrate moieties in positive and negative modes were recorded and interpreted. Collisionally induced decay mass spectra (positive mode) revealed different patterns depending on the charge of the parent ion, attached cations (or ions), the composition, and the sequence of carbohydrate fragments. The most intense peaks (two series) originated from the sequential cleavage of glycoside bonds resulting in charge location on the reducing end (Y series observed for all of the test compounds) or nonreducing end (B series). Hexaethylene glycol chain fragmentation giving rise to the cleavage of the C–O bond remote from the biotin moiety was observed. Other fragment ions lighter than the above by a difference of (C₂H₄O) _n were absent or much smaller. Similar fragmentation was found for all of the nonsulfated biotinylated glycosides with the hexaethylene glycol spacer thus demonstrating that this type of fragmentation was characteristic of such molecular probes. Similar cleavages along with biotin moiety decay via the elimination of H₂S and H₂CS were observed for negative ions in the collisionally induced decay mass spectra of sulfated and neutral molecular probes.     

Thermodynamic Analysis of the Geldanamycin–Hsp90 Interaction in a Whole Cell Lysate Using a Mass Spectrometry-Based Proteomics Approach

Geldanamycin is a natural product with well-established and potent anti-cancer activities. Heat shock protein 90 (Hsp90) is the known target of geldanamycin, which directly binds to Hsp90’s N-terminal ATP binding domain and inhibits Hsp90’s ATPase activity. The affinity of geldanamycin for Hsp90 has been measured in multiple studies. However, there have been large discrepancies between the reported dissociation constants (i.e., K_d values), which have ranged from low nanomolar to micromolar. Here the stability of proteins from rates of oxidation (SPROX) technique was used in combination with an isobaric mass tagging strategy to measure the binding affinity of geldanamycin to unpurified Hsp90 in an MCF-7 cell lysate. The K_d values determined here were dependent on how long geldanamycin was equilibrated with the lysate prior to SPROX analysis. The K_d values determined using equilibration times of 0.5 and 24 h were 1 and 0.03 μM, respectively. These K_d values, which are similar to those previously reported in a geldanamycin–Hsp90 binding study that involved the use of a fluorescently labeled geldanamycin analogue, establish that the slow-tight binding behavior previously observed for the fluorescently labeled geldanamycin analogue is not an artifact of the fluorescent label, but rather an inherent property of the geldanamycin–Hsp90 binding interaction. The slow-tight binding property of this complex may be related to time-dependent conformational changes in Hsp90 and/or to time-dependent chemical changes in geldanamycin, both of which have been previously proposed to explain the slow-tight binding behavior of the geldanamycin–Hsp90 complex.

Open image in new window

Graphical Abstract ?

     

Structural Characterization of Anhydroicaritin Glycosides Using ESI—FT—ICR Mass Spectrometry

Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was used to determine the structures of anhydroicaritin glycosides by the MS/MS experiments of anhydroicaritin glycosides and their methylated derivatives,With high accuracy FT-ICR-MS provides much information about the structures of compounds ,FT-ICR-MS shows the great potential application in the structural characterization of unknown compounds.     

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.     

Fast Determination of Monocyclic Aromatic Hydrocarbons in Ambient Air Using a Portable Gas Chromatography–Photoionization Detector

Many air sampling methods are time consuming and require complex pre-treatment steps. Gas chromatography–photoionization detector (GC–PID) is a rapid method for sampling and analysis. However, although it has been used in a number of studies, its operating conditions and performance parameters have not been optimized systematically. In this study, a GC–PID method for analysis of monocyclic aromatic hydrocarbons in gas samples without pre-concentration or enrichment was developed and optimized. This GC–PID can perform both online and off-line analysis. In online analysis, the sample was pumped directly into a Teflon sample loop (pumped online injection), which resulted in minimal loss of sample. The optimum parameters were as follows: 30-s pumping time, 10 mL min^?1 of carrier gas flow rate, and 40 °C oven temperature. GC–PID was applied to analysis of benzene, toluene and xylene. The calibration curves showed good linearity for online analysis. The results obtained by GC–PID were accurate and reliable, with all the correlation coefficients ≥0.9972 and all the relative standard deviations <3%. A mixture of benzene, toluene, and o-, m-, and p-xylenes was separated satisfactorily in 10 min, except for m- and p-xylene. The performance of the portable GC–PID was compared with that of an ATD–GC–FID for quantification of benzene, toluene and xylene in calibration gas samples, and benzene, toluene, ethylbenzene, and the o-, m-, and p-xylenes in outdoor ambient air. The results indicated that GC–PID with pumped online injection was stable and accurate for analysis of these monocyclic aromatic hydrocarbons.     

Determination of Chromate Ion in Water Using High Performance Capillary Electrophoresis

ThereisarapidIyincreasingdemandforfastandreliableanalyticaImethodsforthedeterminationofchemicaIformsofelementSinenvironmentalsamples.IthaslongbeenknownthatCrfIII)isessentialformammals,however,CrfVI)isconsideredtobeatoxicagent[l].Theanalysisofchromateion(Vl)inenvironmentwaterisusuallyperformedbyusingspephotometryandatomicabsorption,p..tr...ny[2].TheformerneedsfairIylargeamountofsample,pretreatmenLandlonganalysistime.Thelaterequipmentismuchmoreexpensive.InpreviousreportS,chromateisnormaI1…     

Characterization of Phosphatidylethanolamine Molecular Species in Human Blood by On-Line High Performance Liquid Chromatography/Quadrupole-Linear Ion Trap Mass Spectrometry

As an important constituent in the biomembranes, phospholipids (PL) are a complex mixture of molecular species containing a variety of fatty acyl and head group compositions. In addition to their structural role, some phospholipids also participate in biological processes in various     

Characterization of Phosphatidylethanolamine Molecular Species in Human Blood by On-Line High Performance Liquid Chroma-tography/Quadrupole-Linear Ion Trap Mass Spectrometry

Asanimportantconstituentinthebiomem branes ,phospholipids (PL)areacomplexmixtureofmolecularspeciescontainingavarietyoffattya cylandhead groupcompositions .Inadditiontotheirstructuralrole ,somephospholipidsalsopar ticipateinbiologicalprocessesinvariousways…     

Prospects for Using Chromatography–Mass Spectrometry for the Determination of Lipids in Clinical Cardiolipidology

Journal of Analytical Chemistry - Cardiolipidology – a new direction in cardiology – is developing intensively owing to the method of mass spectrometry. This method has acquired...     

Determination of Some Heavy-metal-ions Using a Sulfur Ion Modified BZ Oscillating System

The oscillating reaction as one important phenomenon of nonlinear chemistry has been a focus in recent years. Among all oscillating systems, Belousov-Zhabotinskii (BZ) oscillating system was first found and studied extensively. The mechanism of BZ oscilla…     

Characterization of in Vitro Metabolism of Loganin by Human Intestinal Microflora Using Ultra-High Performance Liquid Chromatography–Quadrupole Time-of-Flight Mass Spectrometry

Human intestinal microbiota comprise a complex biological system with considerable metabolic activity. Various studies have focused on the bioconversion of flavonoids. However, in addition to flavonoids, bioactive components such as iridoids also exist in many natural and traditional Chinese medicines. Little is known about the interactions of the iridoids with bacteria. Loganin, one of the main effective iridoids in the valuable traditional Chinese herbal medicine Cornus officinalis, exhibits various pharmacological activities and biological effects. Human intestinal bacteria were isolated and the conversion capability of loganin was investigated. The metabolites were determined by ultra-high performance liquid chromatography–quadrupole time-of-flight mass spectrometry. Loganin was metabolized to hydrogenated and hydroxylated loganin sulfate, acetylated loganin, loganetin, methylated loganetin, hydrogenated, and hydroxylated loganetin. The metabolic routes and metabolites of loganin were reported for the first time. These metabolites may influence the biological activities of loganin in vivo. Thus, this study provides fundamental information about a traditional Chinese medicine.     

Characterization of the Penetration of the Blood–Brain Barrier by High-Performance Liquid Chromatography (HPLC) Using a Stationary Phase with an Immobilized Artificial Membrane

The biological activity of drugs on organisms is associated with the pharmacokinetic properties, such as the ability to penetrate through environments of varying polarity such as cellular organelles. In this area, particular attention is turned to the physicochemical properties that determine the potential of drugs to pass across the blood–brain barrier and thus to act on the central nervous system. In this study, special effort has been devoted to the simulation of passive diffusion of seven drugs (propranolol, ibuprofen, atenolol, promazine, chlorpromazine, imipramine, and desipramine) through the blood–brain barrier by high-performance liquid chromatography (HPLC) using a column with an immobilized artificial membrane. Gradient reverse elution was used to develop a linear correlation model for the capacity factors k_IAM and the in vivo logarithmic values of brain-to-blood drug concentration ratios (log BB) with R of 0.9851. Eleven additional pharmaceuticals were determined by the same method to predict their potential to penetrate the blood–brain barrier. The reported analytical method represents an alternative tool for rapid and noninvasive assessment of the absorption properties of chemicals, especially for the development of novel drugs. The retention of the studied compounds on the immobilized artificial membrane column was also compared with three other C18-based stationary phases. Herein, the results of the HPLC determination of drugs using an immobilized artificial membrane are briefly discussed with respect to a general application of the method for evaluating a broader spectrum of pharmaceutical compounds.     

Synthesis and Characterization of Ti-ZSM-5 in a Non-alkaline Medium in the Presence of Fluoride Ions

Ti-ZSM-5 was synthesized by hydro thermal crystallization in the presence of fluoride via using a non-alkaline medium. pH values were 5~7. SEM showed perfect Ti-ZSM-5 crystals and a large single crystal growing from the favourable medium. Substitution of titanium for silicon in the ZSM-5 framework led to a decrease of crystal size and of the length/width ratio. Electron microprobe analysis indicated a homogeneous distribution of titanium in the ZSM-5 framework. The unit cell parameters of the Ti-ZSM-5 determined by XRD increased with an increase in titanium content in the framework. TiO4tetrahedron vibrations were found in the IR spectrum. Si(1Ti) peakwas seen in the 29Si MAS NMR spectrum at -1O1ppm(from TMS) and 13CMAS NMR analysis verified the effect of (C3H7)4N F- occluded in thechannels. XPS study on the precursors, calcined and H2O2 adsorbed Ti-ZSM-5 was performed and some interesting results were observed.     

Oxidation of Oxalic Acid in the Ozone–Chloride–Ion Reaction System in an Aqueous Solution

Russian Journal of Physical Chemistry A - It is shown that the rate of oxidation of oxalic acid H2C2O4 during the ozonation of its solutions grows considerably if sodium chloride is added to the...     

The FUNPET—a New Hybrid Ion Funnel-Ion Carpet Atmospheric Pressure Interface for the Simultaneous Transmission of a Broad Mass Range

An atmospheric pressure interface transports ions from ambient pressure to the low-pressure environment of a mass spectrometer. A capillary coupled to an ion funnel is widely used. However, conventional ion funnels do little to negate the large amount of energy picked up by high-mass ions from the gas flow through the capillary. There has been little work done on the effects of gas flow on ion transmission, and the previous studies have all been limited to low-mass, low-charge ions. In this work, we account for the effects of gas flow, diffusion, and electric fields (static and oscillating) on ion trajectories and use simulations to design a new hybrid ion funnel-ion carpet (FUNPET) interface that transmits a broad mass range with a single set of instrument conditions. The design incorporates a virtual jet disruptor where pressure buildup and counter flow dissipate the supersonic jet that results from gas flow into the interface. This, and the small exit aperture that can be used with the FUNPET, reduces the gas flow into the next stage of differential pumping. The virtual jet disruptor thermalizes ions with a broad range of masses (1 kDa to 1 GDa), and once thermalized, they are transmitted into next region of the mass spectrometer with low excess kinetic energy. The FUNPET interface is easy to fabricate from flexible printed circuit board and a support frame made by 3D printing. The performance of the interface was evaluated using charge detection mass spectrometry.

Open image in new window

Graphical Abstract ?

     

Characterization of Minor N-linked Glycans on Antibodies Using Endo H Release and MALDI–Mass Spectrometry

Abstract

A MALDI mass spectrometry method using Bruker Daltonic's LIFT technology for MS/MS analysis has been developed for profiling and characterizing low abundant N-glycans from recombinant immunoglobulin G (IgG) antibodies. In this method, Endoglycosidase H (Endo H) released N-glycans are derivatized at their reducing end with 2-aminobenzamide (2-AB) and separated by normal phase chromatography. Endo H hydrolyses the bond between the two GlcNAc residues of the trimannosyl core of high mannose and hybrid N-linked glycans, leaving the core GlcNAc attached to the protein. High mannose and hybrid type N-glycans are released from the glycoprotein whereas the more abundant, complex biantennary type oligosaccharide structures are unaffected. Analysis of Endo H treated glycan moieties by MALDI mass spectrometry identified several minor species of high mannose and hybrid type glycans. Subsequent MALDI TOF MS/MS analysis of the resulting products yielded information about structural features of the high mannose and hybrid type glycans. This study involving Endo H treatment followed by MALDI mass spectrometry coupled with LIFT technology for MS/MS analysis offers a specific and sensitive technique for visualizing, and characterizing minor glycan species.