A new approach to increase the resolution of the mass spectrometer with wedge-shaped reflectors

T13N4

E.A. Sysoeva, A.V. Spakhov, Alexander A. Sysoev

 The paper describes the investigation of ion-optical properties of a laser TOF mass spectrometer including two successively positioned wedge-shaped ion mirrors. Some specific properties of the configuration of ion trajectories near their reflection in the second ion reflector have been found. The dependence of aberrations on the ion energy was acquired the toothed shape for the resolution of the analyzer higher than 3000-5000. An approximation of the dependence gave a polynom of the 15-th degree. The calculation of polynomial coefficients showed a great contribution into the duration of ion packets for aberrations of higher order. The discovered features allowed us to suggest a way of local correction of nearby trajectories in the full flow of ions. By correcting the local motion of individual groups of ions it was possible to reduce temporary aberration up to 1−1.6 ns depending on the ion energy. For the time of ion flight ~ 35 μs, such duration limits the resolution of the analyzer by a value not less than 10000. The real length of the ion drift path was about 30 cm. The total overall sizes of the ion-optical system were ~ 24 cm × 19 cm × 5 cm.

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T13N4

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Study of gaseous sample ionization by excited particles formed in glow discharge using high resolution orthogonal acceleration time-of-flight mass spectrometer

T13N4

I.V. Sulimenkov, V.S. Brusov, V.V. Zelenov, M.G. Skoblin, V.V. Filatov,
A.R. Pikhtelev, V.I. Kozlovskii

The experimental results of mass spectral analysis of volatile organic compounds in gaseous sample using a new designed of the ion source with Penning ionization by excited metastable atoms of noble gas are presented. To analyze gas flow profile effect on the metastable atom transfer and the reaction efficiency, gas dynamic simulation of the reagent gas flow profile from the discharge zone to the ionization region was performed by ANSYS software. The n-octane and toluene samples diluted with helium at 100 ppb mole concentration were used for our experiments. The resulting mass spectra of n-octane and toluene samples contain far more intensive molecular ions in comparison to the n-octane and toluene electron ionization mass spectra from NIST database. The sensitivity of 5 ions per 1 pg and 130 ions per 1 pg was achieved for n-octane and toluene molecular ions using the developed ion source combined with our mass spectrometer. The corresponding detection limits are 2.3 pg s−1 and 0.08 pg s−1 for n-octane and toluene molecular ions. The detection limit for the reported ion source was considered theoretically.

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The comparison between «low-molecular» and conventional approaches to species identification of bacteria by MALDI mass spectrometry

T13N4

B.L. Milman, V.V. Gostev, A.V. Dmitriev

The new approach to bacteria identification which uses the standard software for building mass spectral libraries of low-molecular compounds and for corresponding library searches, is compared to the conventional approach based on the commercial Biotyper software and database. The results are obtained for the random sample of 100 mass spectra of 25 strains of S. pyogenes, S. dysgalactiae subsp. equisimilis and S. anginosus. The spectra were sampled from the database of 728 mass spectra of 182 strains for some Streptococcus species. Both approaches were proved to result in the similar identification as 80–88 % of true outcomes. For similar reference mass spectra and the same identification criteria, the identification results were very close to each other as 24 agreements for 25 strains. This is the result from that different estimations of the mass spectral similarity included in programs under the comparison lead to the correlation of similarity indicators. A difference of identification results is mainly due to not the same reference databases and also different identification criteria.

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Chemical structure elucidation of gas chromatographic artifact of synthetic cannabinoid N-(1-carbamoyl-2-methylpropyl)-1-(cyclohexylmethyl)-1H-indazol-3-carboxamide by means of high resolution mass spectrometry

T13N4

V.A. Shevyrin

Synthetic cannabinoids are the most popular psychoactive compounds within illegal market. In a course of gas chromatographic determination, some synthetic cannabinoids undergo chemical transformations due to their thermal interaction with chromatographic system. The present paper is devoted to structure elucidation of gas chromatographic artifact formed from synthetic cannabinoid N-(1-carbamoyl-2-methylpropyl)-1-(cyclohexylmethyl)-1H-indazol-3-carboxamide as a result of dehydratation of its terminal carbamoyl moiety. Structure of the artifact was determined by means of high resolution mass spectrometry.

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Determination of methylphosphonic acid in human blood plasma by high-performance liquid chromatography tandem mass spectrometry

T13N4

T.M. Baygildiev, I.A. Rodin, A.N. Stavrianidi, A.V. Braun, O.A. Shpigun, I.V. Rybalchenko

 Using high performance liquid chromatography combined with tandem mass spectrometric detection, an approach for the determination of the most stable nerve agent biomarker, methylphosphonic acid, in human blood plasma has been developed. The proposed method is based on the derivatization reaction of methylphosphonic acid with p-bromophenacyl bromide. Optimization of conditions for human plasma sample preparation, mass spectrometric detection conditiones and gradient elution program has been performed. The proposed approach has demonstrated satisfactory reproducibility and selectivity of the determination, limit of detection for methylphosphonic acid in human plasma was 3 ng ml−1.

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Possibilities for energy pumping in radio-frequency quadrupole by shifted supersonic gas jet. Part I. Accelerated and excited atoms transmission

T13N4

V.V. Raznikov, V.V. Zelenov, E.V. Aparina, A.R. Pikhtelev, I.V. Sulimenkov

Generation of the ion beam and its transmission into a mass analyzer is one of the central problems in mass spectrometry. The use of narrowly directed supersonic gas jet has a number of advantages in comparison with other ways of sampling. The aim of the work is to confirm the declared earlier properties of the jet formed at the output of cylindrical channel when the free path length of gaseous atoms at the beginning of the channel is comparable with the channel diameter. The paper describes ability of such supersonic jet to conserve an additional energy of the jet gas atoms. Significant influence of the temperature of the gas flow on the yield of cyclohexane fragment ions was found, cyclohexane being an admixture in the noble gas jet passing through the electron ionization ion source. Possibility to obtain a stream of metastable electronically excited atoms inside the jet is also shown. The results of the work confirm an availability of the supersonic gas jet to design a high efficiency ion source inside radio-frequency quadrupole at the input of the mass analyzer.

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Identification of regions in apomyoglobin which form intermolecular interactions in amyloid aggregates using high-performance mass spectrometry

T13N4

N.S. Katina, M.Yu. Suvorina, E.I. Grigorashvili, V.V. Marchenkov, N.A. Ryabova, A.D. Nikulin,
A.K. Surin

 Formation of amyloid aggregates in human organs and tissues causes the development of incurable diseases. However experimental studies of the mechanism of amyloid formation by proteins as well as structural characteristics of amyloids are complicated because of heterogeneity and high molecular weight of the aggregates. We have used limited proteolysis and mass spectrometry for identification of regions in the polypeptide chain of apomyoglobin which give rise to intermolecular interactions in amyloid structures. The methods of tandem mass spectroscopy have allowed us to identify regions in the polypeptide chain of myoglobin which form the core of amyloid structures. It is shown that the main structural elements for the formation of the core of amyloid fibrils in myoglobin are regions from amino acid region 60 through 90 and from 97 through 124. These areas coincide well with the theoreticall prediction. The approach has made it possible to obtain important data on the structure of protein molecules in aggregates and on conformational rearrangements of apomyoglobin upon amyloid formation.

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