Gas Chromatographic – Mass Spectrometric Cardiotonic Glycosides Detection in Equine Urine Doping Analysis

A screening method for the detection of cardiotonic glycosides in horse’s urine is presented in this paper. This method is based on the detection by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-high resolution mass spectrometry (GC-HRMS) of the trimethylsilyl (TMS) derivatives of the aglycon moieties of these compounds after solid phase extraction and methanolysis, according to the standard procedure currently used for the screening of anabolic steroids in horses, in the Athens Doping Control Laboratory. This validated method was also applied for the excretion study of digoxin in two mare horses after a single administration of a 75 μg Kg^?1 oral dose, by GC-MS and GC-HRMS.     

Determination of Metformin in Human Plasma by Liquid Chromatography-tandem Mass Spectrometric Assay

Metformin (1,1-dimethylbiguanide) (Fig. 1) i san oral anti-hyperglycemic agent used in the treatment of non-insulin-dependent diabetes mellitus(type Ⅱ ). Owing to its weight-decreasing and serum lipid-normalizing effects, it is especially recommended for obese patients. Various analytical methods have been described for the measurement of metformin in biological fluids,     

Chromato–Mass Spectrometric Identification of Unusual Products of 4-Isopropylphenol Oxidation in Aqueous Solutions

4-Isopropylphenol has been chosen as the simplest object to model the processes of oxidation of organic compounds with air oxygen in aqueous media, since it contains a hydrogen atom at the tertiary carbon atom in the α-position with benzene ring and a hydroxyl group enabling mass-spectrometric detection of the products in the negative ions mode. It has been stated that oxidation of 4-isopropylphenol with air oxygen in aqueous media becomes noticeable as the solution pH approaches the рK_а value of the substrate (10.25). The major product [4-isopropyl-2-(4-isopropylphenoxy)phenol] is formed via nucleophilic addition of the starting 4-isopropylphenol at the intermediate product of its oxidation, quinone methide. Intensity of electrochemical oxidation can be tubed by changing the electrode potential. The highest conversion of 4-isopropylphenol has been observed at potential 1.5–3.0 V, the formed compounds being the products of transformation of the same quinone methide intermediate. The obtained data have explained the formation and diversity of dimeric and oligomeric products of oxidation of natural flavonoids.     

Gas Chromatography–Mass Spectrometric Determination of Traces of Ether-Type Icing Inhibitors in Free-Floating Fuels

A gas chromatographic–mass spectrometric (GC–MS) assay method has been developed for simultaneous determination of ethylene glycol monomethyl ether (EGME) and diethylene glycol monomethyl ether (DEGME) in spilled aviation fuels. Ethylene glycol monobutyl ether (EGBE) and ethylene glycol monoethyl ether (EGEE) were used as internal standard and surrogate, respectively. Sample preparation consisted of back-extraction with 7 mL dichloromethane after extraction of 50 mL of fuel with 2 mL of water. The extract was concentrated to dryness, dissolved in 100 L methanol, and analyzed by GC–MS with selected-ion monitoring (SIM). The peaks had good chromatographic properties on a semi-polar column. EGME and DEGME were extracted from fuel with high recovery of 75 and 85%, with small variations, respectively. Method detection limits were 1.3 and 1.0 ng mL^–1 for EGME and DEGME, respectively, in spilled fuel. DEGME was detected at concentrations of 22.6 and 19.7 ng mL^–1 in two samples from among five free-floating samples collected in a tunnel of a subway station located in the vicinity of an army base in Korea. The method might be useful for differentiation between the fuel-types kerosene and JP-8, which might originate from a storage tank.     

Specific Mass Spectrometric Fragmentations from the Dissociation of Intermediate Ion-Neutral Complexes

Thewhlnolecularreactionsof(radical)canonsaredescribedasinvolvingtileintermediatCformationofanion-neutralcomplexandaproton-boundcomplex,fieldtogethermainlybyelectrostaticforcesl.TillsUleory11asprovedsosuccessfulinresolvingnumerouspuzzlingobservationsofhydrogent~sfersZ,11ydrogenexchanges',isotopicatomPermut3tions',andremotefragmentations',thatithasquicklygainedwideacceptance.Therefore,thefurtherstudyofintermediateion-neutralcomplexesisofinterestforabetterunderStandingOftheilleoryandapplication…     

High Temperature Mass Spectrometric Study of the TiO2–Al2O3 System

Russian Journal of General Chemistry - The results of studying the evaporation and thermodynamic properties of the TiO2–Al2O3 system in the temperature range 2250–2710 K by...     

Liquid Chromatography‐Electrospray Ionization Mass Spectrometric Method for Determination of Gliclazide in Human Plasma

Abstract

A rapid, sensitive, and specific liquid chromatography‐electrospray ionization mass spectrometric (LC‐ESI‐MS) method has been developed for quantification of gliclazide in human plasma. The analyte and tolbutamide (internal standard, I.S.) were extracted from plasma samples with n‐hexane–dichloromethane (1:1, v/v) and analyzed on a C₁₈ column. The chromatographic separation was achieved within 4.0 min by using methanol–0.5% formic acid (80:20, v/v) as mobile phase and the flow rate was 1.0 mL/min. Ion signals m/z 324.0 and 271.0 for gliclazide and internal standard were measured in the positive mode, respectively. The method was linear within the range of 2.5–2000 ng/mL. The lower limit of quantification (LLOQ) was 2.5 ng/mL. The intra‐ and inter‐day precisions were lower than 2.8% in terms of relative standard deviation (RSD). The inter‐day relative error (RE) as determined from quality control samples (QCs) ranged from ?1.93% to 1.85%. This validated method was successfully applied for the evaluation of pharmacokinetic profiles of gliclazide modified‐release tablets in 20 healthy volunteers.     

Protein–Protein Binding Affinities in Solution Determined by Electrospray Mass Spectrometry

Electrospray ionization (ESI) allows the transfer of multi-protein complexes into the gas phase, thereby providing a simple approach for monitoring the stoichiometry of these noncovalent assemblies by mass spectrometry (MS). It remains unclear, however, whether the measured ion abundance ratios of free and bound species are suitable for determining solution-phase binding affinities (K _d values). Many types of mass spectrometers employ rf-only quadrupoles as ion guides. This work demonstrates that the settings used for these devices are a key factor for ensuring uniform transmission behavior, which is a prerequisite for meaningful affinity measurements. Using bovine β-lactoglobulin and hemoglobin as model systems, it is demonstrated that under carefully adjusted conditions the “direct” ESI-MS approach is capable of providing K _d values that are in good agreement with previously published solution-phase data. Of the several ion sources tested, a regular ESI emitter operated with pressure-driven flow at 1 μL min^–1 provided the most favorable results. Potential problems in these experiments include conformationally-induced differences in ionization efficiencies, inadvertent collision-induced dissociation, and ESI-induced clustering artifacts. A number of simple tests can be conducted to assess whether or not these factors are prevalent under the conditions used. In addition, the fidelity of the method can be scrutinized by performing measurements over a wide concentration range. Overall, this work supports the viability of the direct ESI-MS approach for determining binding affinities of protein–protein complexes in solution.     

Sequence Analysis of Polypeptide by Mass Spectrometry

The method described in this work provides a sensitive and fast technique for investigating the primary structure of peptides with molecular weight up to 3340 amu. Usually, the metastable ion kinetic energy spectra (MIKES) and collisional activated decomposition (CAD) spectra provide complementary information for the FAB mass spectra, the MIKES and CAD spectra generally contain high-mass sequence ions.     

Study on the Enhancement of Proton Affinity by N-Diisopropyloxy Phosphorylation of Amino Acid in Mass Spectrometry

With introduction of a diisopropyloxy phosphoryl group into the N terminal of amino acids,it was found that proton affinity(PA) of amino acid was enhanced in mass spectrometry.Density functional theory calculations showed that the energy for protonation of DIPP-amino acid is lower than that of amino acid,which means PA of DIPP-AA ishigher than that of corresponding amino acid.These results.Coincident with our empirical results.offer a useful interpretation of experimental observations.     

Rapid Analysis of Ingredients in Cream Using Ultrasonic Mist–Direct Analysis in Real-Time Time-of-Flight Mass Spectrometry

A novel method for the simultaneous detection of ingredients in pharmaceutical applications such as creams and lotions was developed. An ultrasonic atomizer has been used to produce a mist containing ingredients. The analyte molecules in the mist can be ionized by using direct analysis in real time (DART) at lower temperature than traditionally used, and we thus solved the problem of normal DART-MS measurement using a high-temperature gas. Thereby, molecular-related ions of heat-unstable components and nonvolatile components became detectable. The deprotonated molecular ion of glycyrrhizic acid (m/z 821), which is unstable at high temperatures, was detected without pyrolysis by ultrasonic mist–DART-MS using unheated helium gas, although it was not detected by normal DART-MS using heated helium gas. The cationized molecular ions of derivatives of polyethylene glycol fatty acid monoesters, which are nonvolatile compounds, were also detected as m/z peaks observed from 800 to 2300. Although the protonated molecular ion of tocopherol acetate was not detected in ionization by ultrasonic mist, it was detected by ultrasonic mist–DART-MS even in the emulsion. It was not necessary to dissolve a sample completely to detect its ions. This method enabled us to obtain the composition of pharmaceutical applications simply and rapidly.

Open image in new window

Graphical Abstract ?

     

Characterization of [2Fe–2S]-Cluster-Bridged Protein Complexes and Reaction Intermediates by use of Native Mass Spectrometric Methods

Many iron–sulfur proteins involved in cluster trafficking form [2Fe–2S]-cluster-bridged complexes that are often challenging to characterize because of the inherent instability of the cluster at the interface. Herein, we illustrate the use of fast, online buffer exchange coupled to a native mass spectrometry (OBE nMS) method to characterize [2Fe–2S]-cluster-bridged proteins and their transient cluster-transfer intermediates. The use of this mechanistic and protein-characterization tool is demonstrated with holo glutaredoxin 5 (GLRX5) homodimer and holo GLRX5:BolA-like protein 3 (BOLA3) heterodimer. Using the OBE nMS method, cluster-transfer reactions between the holo-dimers and apo-ferredoxin (FDX2) are monitored, and intermediate [2Fe–2S] species, such as (FDX2:GLRX5:[2Fe–2S]:GSH) and (FDX2:BOLA3:GLRX5:[2Fe–2S]:GSH) are detected. The OBE nMS method is a robust technique for characterizing iron–sulfur-cluster-bridged protein complexes and transient iron–sulfur-cluster transfer intermediates.     

Validation of a Gas Chromatographic–Tandem Mass Spectrometric Method for Analysis of Pesticide Residues in Six Food Commodities. Selection of a Reference Matrix for Calibration

A gas chromatographic–tandem mass spectrometric (GC–MS–MS) method for analysis of 30 multi-class pesticide residues in four vegetables (cucumber, marrow, pepper, and eggplant) and two fruits (melon and watermelon) has been developed and validated. The performance characteristics linearity, detection limit (LOD), quantification limit (LOQ), precision, and recovery were studied. The effect of the matrix on the calibration step was studied by comparing calibration curves and recoveries for each food commodity. Two different food commodities, cucumber and watermelon, were selected as potential reference matrixes for the target vegetables and fruits, respectively.     

Mirion—A Software Package for Automatic Processing of Mass Spectrometric Images

Mass spectrometric imaging (MSI) techniques are of growing interest for the Life Sciences. In recent years, the development of new instruments employing ion sources that are tailored for spatial scanning allowed the acquisition of large data sets. A subsequent data processing, however, is still a bottleneck in the analytical process, as a manual data interpretation is impossible within a reasonable time frame. The transformation of mass spectrometric data into spatial distribution images of detected compounds turned out to be the most appropriate method to visualize the results of such scans, as humans are able to interpret images faster and easier than plain numbers. Image generation, thus, is a time-consuming and complex yet very efficient task. The free software package “Mirion,” presented in this paper, allows the handling and analysis of data sets acquired by mass spectrometry imaging. Mirion can be used for image processing of MSI data obtained from many different sources, as it uses the HUPO-PSI-based standard data format imzML, which is implemented in the proprietary software of most of the mass spectrometer companies. Different graphical representations of the recorded data are available. Furthermore, automatic calculation and overlay of mass spectrometric images promotes direct comparison of different analytes for data evaluation. The program also includes tools for image processing and image analysis.

Gas Liquid Chromatographic—Mass Spectrometric Methods for Quantitation of Prostaglandin Analogs

Abstract

The synthesis of tetradeuterated 15-methyl-PGF_2α and 17-phenyl-18, 19, 20-trinor-PGF_2α, is described. Gas chromatographic -mass spectrometric methods, using the deuterated compounds as internal standards and carriers, for quantitation of corresponding unlabeled prostaglandin analogues is described. With acceptable accuracy and precision the sensitivity is in the subpicomole range.     

High Performance Liquid Chromatography—Tandem Mass Spectrometric Determination of Resveratrol and Its Metabolites in Rat Tissues

In this study, we established a rapid, sensitive, and specific liquid chromatography method coupled with electrospray ionization–tandem mass spectrometry to evaluate the disposition of resveratrol and its metabolites in rat tissues following oral administration. Here, we validate this method and show that it is useful for quantifying tissue concentrations of resveratrol and its metabolites with acceptable specificity, linearity, lower limits of quantification, precision, accuracy, and recovery. The present study demonstrates that the major distribution of the trans-resveratrol and its metabolites in investigated tissues, which suggests that there is a specified range of target organs for cancer chemoprevention by polyphenols.     

Prokaryotic Expression, Purification, Antibody Production of a NH2 -Terminal Fragment of mCLCA3 Protein and Analysis of mClCA3 Protein Expression in Asthmatic Mouse Lung

mCLCA3 is a member of calcium activated chloride channel(CACC)family that may play an important role in mucin packaging and secretion in asthmatic and cystic fibrosis lung.To study the protein structure and expression of mCLCA3 in asthmatic mouse lung,an N-terminal 269 amino acid peptide of mCLCA3 was expressed in E.coli,purified to homogeneity and rabbit polyclonal antibodies against this peptide were generated.Immunohistochemistry of asthmatic mouse lung using the antibody indicated exclusive mCLCA3 expression in mucin granules of goblet cells in airway surface and lumen.Immunoblot analysis of lavage fluid from asthmatic mouse lung revealed a single 90 kDa protein form of mClCA3.The results demonstrate that the 90 kDa N-terminal peptide,neither the full-length protein nor the reported N-terminal 35 kDa cleaved form of mClCA3 is the major functional form involved in the packaging and exocytosis of mucin granules in asthmatic goblet cells.     

A Mass Spectrometric Study of γ－Amino－group－containing Propyltriethoxysilanes

ＡＭａｓｓＳｐｅｃｔｒｏｍｅｔｒｉｃＳｔｕｄｙｏｆγ－Ａｍｉｎｏ－ｇｒｏｕｐ－ｃｏｎｔａｉｎｉｎｇＰｒｏｐｙｌｔｒｉｅｔｈｏｘｙｓｉｌａｎｅｓＬｉｎＪｉ－Ｍａｏ；ＨｕａｎｇＷｅｎ－Ｔａｏ；ＦａｎｇＬｉ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，Ｓｈ...     

Comment on “Ion Implantation Standards as a Spark Source Mass Spectrometric Surface Analysis Calibration Technique”

Abstract

While it is pleasing to note that ion implantation standards are being applied to yet another instrumental method for elemental near-surface analysis, it is unfortunate that the concept of using ion implantation for the manufacture of calibration standards has had to be re-invented. More regrettable than the (surely unintentional) omission to acknowledge earlier work^1–6 on the subject though, is the neglect of the authors to provide evidence for their assertion that “the implant dose was measured to an accuracy of better than 5%”. This would be unlikely with the ion current integration mode of dose measurement used by the authors, because significant backscattering of the very much lighter incident ¹¹B⁺ ion from the Zircaloy target in predominantly neutral form should render the dose calculation more inaccurate than this. Evidence of substantial backscattering is provided by the authors themselves in the form of the measured depth profiles of implanted ¹¹B shown in their Fig. 1, viz., extrapolation of these depth profiles into the vaccum side of the surface provides a means of estimating roughly the dose fractio lost by backscatteing. From the data the extrapolted loss fraction would appear to be not less than 5%. On the basis of other independent more direct experimental evidence⁷ it would appear that the backscattered fraction should be about 8% (taking the “equivalent” case - same reduced energy ? and mass ratio - of 500 keV ²⁴Na⁺ bombardment of Au, and adjusting it by the proportionality factor A₁ ^½/Z₁ ^? of Vukaní and Sigmund⁸). This same percentage value is also derived from both theoretical and experimental proton backscattering data provided in ref. 83. The fact that the backscattered fraction is virturally independent of dose for low concentrations of implanted ¹¹B precludes detection of this effect by comparison of dose-equivalent ion microprobe signals of 11_B used by the authors. Therefore, the statement by the authors that “the accuracy of the standards was verified using an ARL ion microprobe mass analyser (IMMA)” is unsubstantiate. At best, the IMMA measurements provide an indication that implantation-associated dose-dependent re-sputtering of implanted ¹¹B is negligible for the doses used by the authors. But this fortunate state of affairs is attributable solely to the unusually low sputtering yield for the combination boron/Zircaloy. In this connection it is important to point out that for many other combinations the fractional loss by re-sputtering of the implanted ion in the energy region under discussion is in considerable excess of 5% for the doses used by the authors; and this not take into account any possible loss inrease that may be caused by bombardment-induced radiation-enhanced diffusion towards the surface. Calculation of the minimum re-sputtering loss is possible with an algorith developed by gries^3,9.