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Sample records for helium desorption spectrometry

  1. Defects and morphological changes in nanothin Cu films on polycrystalline Mo analyzed by thermal helium desorption spectrometry

    SciTech Connect

    Venugopal, V.; Seijbel, L.J.; Thijsse, B.J.

    2005-07-15

    Thermal helium desorption spectrometry (THDS) has been used for the investigation of defects and thermal stability of thin Cu films (5-200 A ) deposited on a polycrystalline Mo substrate in ultrahigh vacuum. These films are metastable at room temperature. On heating, the films transform into islands, giving rise to a relatively broad peak in the helium desorption spectra. The temperature of this island formation is dependent on film thickness, being 417 K for 10 A and 1100 K for a 200 A film. The activation energy for island formation was found to be 0.3{+-}0.1 eV for 75 A film. Grain boundaries have a strong effect on island formation. The defect concentration in the as-deposited films is {approx}5x10{sup -4}, for films thicker than 50 A and more for thinner films. Helium release from monovacancies was identified in the case of a 200 A film. Helium release was also seen during sublimation of the Cu film ({approx}1350 K). Overlayer experiments were used to identify helium trapped close to the film surface. An increase of the substrate temperature during deposition resulted in a film that had already formed islands. Argon-ion assistance (250 eV) during film deposition with an ion/atom ratio of {approx}0.1 resulted in a significant enhancement of helium trapping in the films. The argon concentration in the films was found to be 10{sup -3}. The temperature of island formation was increased due to argon-ion assistance. The helium and argon desorption spectra are found to be similar, which is due to most of the helium becoming trapped in the defects created by the argon beam. The role of the Mo surface in affecting the defects at the film-substrate interface is investigated. The effect of variation of helium fluence and helium implantation energy is also considered. The present THDS results of Cu/poly-Mo are compared to those of Cu/Mo(100) and Cu/Mo(100) reported earlier.

  2. Thermal desorption behavior of helium in aged titanium tritide films

    NASA Astrophysics Data System (ADS)

    Cheng, G. J.; Shi, L. Q.; Zhou, X. S.; Liang, J. H.; Wang, W. D.; Long, X. G.; Yang, B. F.; Peng, S. M.

    2015-11-01

    The desorption behavior of helium in TiT(1.5∼1.8)-x3Hex film samples (x = 0.0022-0.22) was investigated by thermal desorption technique in vacuum condition in this paper. The thermal helium desorption spectrometry (THDS) of aging titanium tritide films prepared by electron beam evaporation revealed that, depending on the decayed 3He concentration in the samples, there are more than four states of helium existing in the films. The divided four zones in THDS based on helium states represent respectively: (1) the mobile single helium atoms with low activation energy in all aging samples resulted from the interstitial sites or dissociated from interstitial clusters, loops and dislocations, (2) helium bubbles inside the grain lattices, (3) helium bubbles in the grain boundaries and interconnected networks of dislocations in the helium concentration of 3Hegen/Ti > 0.0094, and (4) helium bubbles near or linked to the film surface by interconnected channel for later aging stage with 3Hegen/Ti > 0.18. The proportion of helium desorption in each zone was estimated, and dissociated energies of helium for different trapping states were given.

  3. Absolute number densities of helium metastable atoms determined by atomic absorption spectroscopy in helium plasma-based discharges used as ambient desorption/ionization sources for mass spectrometry

    NASA Astrophysics Data System (ADS)

    Reininger, Charlotte; Woodfield, Kellie; Keelor, Joel D.; Kaylor, Adam; Fernández, Facundo M.; Farnsworth, Paul B.

    2014-10-01

    The absolute number densities of helium atoms in the 2s 3S1 metastable state were determined in four plasma-based ambient desorption/ionization sources by atomic absorption spectroscopy. The plasmas included a high-frequency dielectric barrier discharge (HF-DBD), a low temperature plasma (LTP), and two atmospheric-pressure glow discharges, one with AC excitation and the other with DC excitation. Peak densities in the luminous plumes downstream from the discharge capillaries of the HF-DBD and the LTP were 1.39 × 1012 cm- 3 and 0.011 × 1012 cm- 3, respectively. Neither glow discharge produced a visible afterglow, and no metastable atoms were detected downstream from the capillary exits. However, densities of 0.58 × 1012 cm- 3 and 0.97 × 1012 cm- 3 were measured in the interelectrode regions of the AC and DC glow discharges, respectively. Time-resolved measurements of metastable atom densities revealed significant random variations in the timing of pulsed absorption signals with respect to the voltage waveforms applied to the discharges.

  4. Plasma Desorption Mass Spectrometry: Coming of Age.

    ERIC Educational Resources Information Center

    Cotter, Robert J.

    1988-01-01

    Discusses the history and development of Plasma Desorption Mass Spectrometry to determine molecular weights and structures of proteins and polymers. Outlines theory, instrumentation, and sample preparation commonly used. Gives several examples of resulting spectra. (ML)

  5. Laser-desorption mass spectrometry/mass spectrometry and the mechanism of desorption ionization

    SciTech Connect

    Zakett, D.; Schoen, A.E.; Cooks, R.G.; Hemberger, P.H.

    1981-03-11

    This paper reports sucrose mass spectra obtained by combining laser desorption with mass spectrometry/mass spectrometry. Remarkable similarities in fragmentation behavior with secondary ion mass spectra (SIMS) provide evidence for mechanistic similarities between SIMS and laser desorption (LD). Attachment of alkali metals to organic molecules (cationization) is a common feature of desorption ionization. This process also occurs during laser desorption of involatile compounds which further indicates the existence of underlying similarities between LD and SIMS. Steady ion currents (several thousand ions per laser pulse) of cationized sucrose are obtained for relatively long periods (minutes).

  6. Preparation and thermal desorption properties of dc sputtered zirconium-hydrogen-helium thin films

    SciTech Connect

    Wei, Y. C.; Shi, L. Q.; Zhang, L.; He, Z. J.; Zhang, B.; Wang, L. B.

    2008-11-15

    We developed a new approach for preparing hydrogen and helium co-containing zirconium films (Zr-H-He) to simulate aging metal tritides. We also studied the effect of hydrogen on helium behavior, in which we applied direct current magnetron sputtering in a mixture of working gases (helium, argon, and hydrogen). The amount and depth profile of helium and hydrogen trapped in the films were determined using the elastic recoil detection analysis. The microstructure and surface morphology of the Zr-H-He films were studied by x-ray diffraction, transmission electron microscopy, and atomic force microscopy. To investigate the effect of hydrogen on the thermal release behavior of helium in the Zr film, thermal desorption spectrometry (TDS) was used, which revealed a similar desorption behavior to aged tritides. TDS experiments showed that the spectra were constituted by low-temperature peaks around 300 deg. C and high temperature peaks above 750 deg. C. Furthermore, the solid-phase {alpha} to {delta} transformation changed the shapes of the high-temperature peaks related to microstates of helium bubbles and caused the peak with a massive helium release shift toward lower temperature obviously.

  7. Thermal desorption spectra from cavities in helium-implanted silicon

    NASA Astrophysics Data System (ADS)

    Cerofolini, G. F.; Calzolari, G.; Corni, F.; Frabboni, S.; Nobili, C.; Ottaviani, G.; Tonini, R.

    2000-04-01

    Thermal desorption spectra at constant ramp rate have been determined after helium implantation into bare silicon prepared for a large set of experimental conditions. The spectra can phenomenologically be classified as composed by two peaks: the α peak, centered on a temperature of 750-800°C with a shoulder extending to lower temperature (down to 550°C), and the β peak, centered on a lower temperature depending on the implantation-annealing conditions. The α peak is attributed to the emission from cavities, while the β peak is attributed to the emission from vacancylike defects. A detailed theory describing helium effusion from stable cavities as controlled by the interatomic helium-helium potential is proposed and found to reproduce accurately most of the α peaks. The postimplantation of hydrogen into samples displaying a pure β emission results in an α peak which can be described by the same model as above provided that the cavities are unstable and shrink during desorption in such a way as to maintain constant the concentration of contained helium.

  8. DEUTERIUM, TRITIUM, AND HELIUM DESORPTION FROM AGED TITANIUM TRITIDES. PART I.

    SciTech Connect

    Shanahan, K; Jeffrey Holder, J

    2006-07-10

    Six new samples of tritium-aged bulk titanium have been examined by thermal desorption and isotope exchange chemistry. The discovery of a lower temperature hydrogen desorption state in these materials, previously reported, has been confirmed in one of the new samples. The helium release of the samples shows the more severe effects obtained from longer aging periods, i.e. higher initial He/M ratios. Several of the more aged samples were spontaneously releasing helium. Part I will discuss the new results on the new lower temperature hydrogen desorption state found in one more extensively studied sample. Part II will discuss the hydrogen/helium release behavior of the remaining samples.

  9. DEUTERIUM, TRITIUM, AND HELIUM DESORPTION FROM AGED TITANIUM TRITIDES. PART II.

    SciTech Connect

    Shanahan, K; Jeffrey Holder, J

    2006-08-17

    Six new samples of tritium-aged bulk titanium have been examined by thermal desorption and isotope exchange chemistry. The discovery of a lower temperature hydrogen desorption state in these materials, previously reported, has been confirmed in one of the new samples. The helium release of the samples shows the more severe effects obtained from longer aging periods, i.e. higher initial He/M ratios. Several of the more aged samples were spontaneously releasing helium. Part I discussed the new results on the new lower temperature hydrogen desorption state found in one more extensively studied sample. Part II will discuss the hydrogen/helium release behavior of the remaining samples.

  10. Laser desorption mass spectrometry for biomolecule detection and its applications

    NASA Astrophysics Data System (ADS)

    Winston Chen, C. H.; Sammartano, L. J.; Isola, N. R.; Allman, S. L.

    2001-08-01

    During the past few years, we developed and used laser desorption mass spectrometry for biomolecule detections. Matrix-assisted laser desorption/ionization (MALDI) was successfully used to detect DNA fragments with the size larger than 3000 base pairs. It was also successfully used to sequence DNA with both enzymatic and chemical degradation methods to produce DNA ladders. We also developed MALDI with fragmentation for direct DNA sequencing for short DNA probes. Since laser desorption mass spectrometry for DNA detection has the advantages of fast speed and no need of labeling, it has a great potential for molecular diagnosis for disease and person identification by DNA fingerprinting. We applied laser desorption mass spectrometry to succeed in the diagnosis of cystic fibrosis and several other nerve degenerative diseases such as Huntington's disease. We also succeeded in demonstrating DNA typing for forensic applications.

  11. In situ probing of helium desorption from individual nanobubbles under electron irradiation

    SciTech Connect

    David, M.-L.; Pailloux, F.; Mauchamp, V.; Pizzagalli, L.

    2011-04-25

    The understanding of the mechanisms of helium bubble formation and evolution in materials requires the quantitative determination of several key quantities such as the helium density in the bubbles. Helium nanobubbles of about 16 nm in diameter were created in silicon by helium implantation at high fluence and subsequent annealing. Individual nanobubbles were analyzed by spatially resolved Electron Energy-loss Spectroscopy (EELS). We report on the in situ probing of helium desorption from the nanobubbles under electron irradiation. This opens new perspectives for a more accurate determination of the helium density through spatially resolved EELS.

  12. Graphene matrix for signal enhancement in ambient plasma assisted laser desorption ionization mass spectrometry.

    PubMed

    Chang, Cuilan; Li, Xianjiang; Bai, Yu; Xu, Gege; Feng, Baosheng; Liao, Yiping; Liu, Huwei

    2013-09-30

    In this work, the signal intensity of ambient plasma assisted laser desorption ionization mass spectrometry (PALDI-MS) was significantly increased with graphene as matrix. The graphene functions as a substrate to trap analytes, absorb energy from the visible laser irradiation and transfer energy to the analytes to facilitate the laser desorption process. The desorbed analytes are further ionized by helium plasma and analyzed by MS. Compared with a traditional organic matrix, α-cyano-4-hydroxycinnamic acid (CHCA), graphene exhibited much higher desorption efficiency for most of the compounds benefitting from the strong optical absorption at 532nm. The performance has been confirmed by the facile analysis of more than forty compounds with various structures. Additionally, this method was successfully applied to distinguish three kinds of Chinese tea leaves by detecting the endogenous caffeine and theanine, which proved the utility, facility and convenience of this method for rapid screening of main components in real samples. PMID:23953441

  13. Charge Assisted Laser Desorption/Ionization Mass Spectrometry of Droplets

    PubMed Central

    Jorabchi, Kaveh; Westphall, Michael S.; Smith, Lloyd M.

    2008-01-01

    We propose and evaluate a new mechanism to account for analyte ion signal enhancement in ultraviolet-laser desorption mass spectrometry of droplets in the presence of corona ions. Our new insights are based on timing control of corona ion production, laser desorption, and peptide ion extraction achieved by a novel pulsed corona apparatus. We demonstrate that droplet charging rather than gas-phase ion-neutral reactions is the major contributor to analyte ion generation from an electrically isolated droplet. Implications of the new mechanism, termed charge assisted laser desorption/ionization (CALDI), are discussed and contrasted to those of the laser desorption atmospheric pressure chemical ionization method (LD-APCI). It is also demonstrated that analyte ion generation in CALDI occurs with external electric fields about one order of magnitude lower than those needed for atmospheric pressure matrix assisted laser desorption/ionization or electrospray ionization of droplets. PMID:18387311

  14. Counting Molecules by Desorption Ionization and Mass Spectrometry/Mass Spectrometry.

    ERIC Educational Resources Information Center

    Cooks, R. G.; Busch, K. L.

    1982-01-01

    Discusses two newer methods in mass spectrometry and shows how they can increase signal and signal-to-noise ratios, respectively. The first method, desorption ionization (DI), increases sensitivity while the second method, mass spectrometry/mass spectrometry (MS/MS), increases specificity. Together, the two methods offer improved analytical…

  15. Helium reemission, desorption and microstructure evolution of graphites under helium ion implantation

    NASA Astrophysics Data System (ADS)

    Alimov, V. Kh.; Scherzer, B. M. U.; Chernikov, V. N.; Ullmaier, H.

    1995-07-01

    Helium reemission, trapping, and thermal desorption from highly ordered pyrolytic graphite (HOPG and HPG) of different orientation, polycrystalline graphite (EK98), and titanium doped graphite (RG-Ti-91) have been measured at irradiation temperatures of 300 K and 800 K. The implantation was performed with a 40 keV 4He ion beam. Detailed transmission electron microscopy (TEM) investigation of the microstructure evolution was made on the implanted specimens. He reemission from basal oriented (BO) highly oriented pyrolytic graphite is accompanied by blistering and flaking leading to repetitive gas bursts. On edge oriented (EO) pyrolytic graphite three reemission peaks are observed during room temperature implantation, the first and smallest one being assigned to He release from intrinsic lenticular cavities, the second one occurs during early bubble formation when a small amount of implanted gas still escapes accumulation, and the third and largest peak being due to He release by bubble coalescence. The He reemission rate grows very slowly at room temperature and does not reach 100% up to the highest implanted fluence of 3.5ṡ1018 He/cm2. At 800 K the He reemission rate from EO pyrolytic graphite reaches 100% immediately after starting implantation due to the high diffusive mobility of He. EK98 and RG-Ti-91 show similar reemission behaviour. No gas bursts due to blistering are observed. The initial reemission rate at 300 K is higher than in EO pyrolytic graphite due to release of He via a network of intergranular channels. At 800 K reemission is rather similar to that from EO pyrolytic graphite. No thermal desorption of He from BO HOPG up to 1200 K is observed for implanted fluences ≤1016 He/cm2. At higher fluences the onset temperature of desorption decreases from 750 K at 2ṡ1016 He/cm2 to 380 K at 1017 He/cm2 caused by thermal flaking due to pressure increase of He in submicroscopic cracks. In the other materials two desorption peaks are observed, the first one

  16. Quantitative matrix-assisted laser desorption/ionization mass spectrometry

    PubMed Central

    Roder, Heinrich; Hunsucker, Stephen W.

    2008-01-01

    This review summarizes the essential characteristics of matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (TOF MS), especially as they relate to its applications in quantitative analysis. Approaches to quantification by MALDI-TOF MS are presented and published applications are critically reviewed. PMID:19106161

  17. Desorption electrospray ionization-mass spectrometry of proteins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Desorption electrospray ionization-mass spectrometry (DESI-MS) was evaluated for the detection of proteins ranging in molecular mass from 12 to 66 kDa. Proteins were uniformly deposited on a solid surface without pretreatment and analyzed with a DESI source coupled to a quadrupole ion trap mass spec...

  18. Desorption electrospray ionization mass spectrometry of intact bacteria

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Desorption electrospray ionization (DESI) mass spectrometry (MS) was used to differentiate 7 bacterial species based on their measured DESI-mass spectral profile. Both Gram positive and Gram negative bacteria were tested and included Escherichia coli, Staphyloccocus aureus, Enterococcus sp., Bordete...

  19. Laser desorption postionization mass spectrometry imaging of biological targets.

    PubMed

    Akhmetov, Artem; Bhardwaj, Chhavi; Hanley, Luke

    2015-01-01

    Laser desorption photoionization mass spectrometry (LDPI-MS) utilizes two separate light sources for desorption and photoionization of species from a solid surface. This technique has been applied to study a wide variety of molecular analytes in biological systems, but is not yet available in commercial instruments. For this reason, a generalized protocol is presented here for the use of LDPI-MS imaging to detect small molecules within intact biological samples. Examples are provided here for LDPI-MS imaging of an antibiotic within a tooth root canal and a metabolite within a coculture bacterial biofilm. PMID:25361678

  20. Gas Diffusion in Metals: Fundamental Study of Helium-Point Defect Interactions in Iron and Kinetics of Hydrogen Desorption from Zirconium Hydride

    NASA Astrophysics Data System (ADS)

    Hu, Xunxiang

    The behavior of gaseous foreign species (e.g., helium and hydrogen), which are either generated, adsorbed or implanted within the structural materials (e.g., iron and zirconium) exposed to irradiation environments, is an important and largely unsolved topic, as they intensively interact with the irradiation-induced defects, or bond with the lattice atoms to form new compounds, and impose significant effects on their microstructural and mechanical properties in fission and fusion reactors. This research investigates two cases of gas diffusion in metals (i.e., the helium-point defect interactions in iron and kinetics of hydrogen desorption from zirconium hydride) through extensive experimental and modeling studies, with the objective of improving the understanding of helium effects on the microstructures of iron under irradiation and demonstrating the kinetics of hydrogen diffusion and precipitation behavior in zirconium that are crucial to predict cladding failures and hydride fuel performance. The study of helium effects in structural materials aims to develop a self-consistent, experimentally validated model of helium---point defect, defect cluster and intrinsic defects through detailed inter-comparisons between experimental measurements on helium ion implanted iron single crystals and computational models. The combination of thermal helium desorption spectrometry (THDS) experiment with the cluster dynamic model helps to reveal the influence of impurities on the energetics and kinetics of the He-defect interactions and to realize the identification of possible mechanisms governing helium desorption peaks. Positron annihilation spectroscopy is employed to acquire additional information on He-vacancy cluster evolution, which provides an opportunity to validate the model qualitatively. The inclusion of He---self-interstitial clusters extends the cluster dynamic model while MD simulations explore the effects of dislocation loops on helium clustering. In addition, the

  1. First-principles calculations of helium and neon desorption from cavities in silicon.

    PubMed

    Eddin, A Charaf; Pizzagalli, L

    2012-05-01

    Combining density functional theory, the nudged elastic band technique, and the ultradense fluid model, we investigated the desorption process of He and Ne in silicon. Our results show that the internal surfaces of gas-filled bubbles are not a limiting factor during desorption experiments, since the surface reconstruction opens diffusion paths easier than in the bulk. We show that the vibrational contribution to the energy of helium in the bulk has to be considered in order to determine realistic pressures in the bubbles, when comparing experiments and simulations. At the maximum of desorption, an average pressure of 1-2 GPa is computed. PMID:22481168

  2. Ambient diode laser desorption dielectric barrier discharge ionization mass spectrometry of nonvolatile chemicals.

    PubMed

    Gilbert-López, Bienvenida; Schilling, Michael; Ahlmann, Norman; Michels, Antje; Hayen, Heiko; Molina-Díaz, Antonio; García-Reyes, Juan F; Franzke, Joachim

    2013-03-19

    In this work, the combined use of desorption by a continuous wave near-infrared diode laser and ionization by a dielectric barrier discharge-based probe (laser desorption dielectric barrier discharge ionization mass spectrometry (LD-DBDI-MS)) is presented as an ambient ionization method for the mass spectrometric detection of nonvolatile chemicals on surfaces. A separation of desorption and ionization processes could be verified. The use of the diode laser is motivated by its low cost, ease of use, and small size. To achieve an efficient desorption, the glass substrates are coated at the back side with a black point (target point, where the sample is deposited) in order to absorb the energy offered by the diode laser radiation. Subsequent ionization is accomplished by a helium plasmajet generated in the dielectric barrier discharge source. Examples on the application of this approach are shown in both positive and negative ionization modes. A wide variety of multiclass species with low vapor pressure were tested including pesticides, pharmaceuticals and explosives (reserpine, roxithromycin, propazine, prochloraz, spinosad, ampicillin, dicloxacillin, enrofloxacin, tetracycline, oxytetracycline, erythromycin, spinosad, cyclo-1,3,5,7-tetramethylene tetranitrate (HMX), and cyclo-1,3,5-trimethylene trinitramine (RDX)). A comparative evaluation revealed that the use of the laser is advantageous, compared to just heating the substrate surface. PMID:23419061

  3. Unexpected Analyte Oxidation during Desorption Electrospray Ionization - Mass Spectrometry

    SciTech Connect

    Pasilis, Sofie P; Kertesz, Vilmos; Van Berkel, Gary J

    2008-01-01

    During the analysis of surface spotted analytes using desorption electrospray ionization mass spectrometry (DESI-MS), abundant ions are sometimes observed that appear to be the result of oxygen addition reactions. In this investigation, the effect of sample aging, the ambient lab environment, spray voltage, analyte surface concentration, and surface type on this oxidative modification of spotted analytes, exemplified by tamoxifen and reserpine, during analysis by desorption electrospray ionization mass spectrometry was studied. Simple exposure of the samples to air and to ambient lighting increased the extent of oxidation. Increased spray voltage lead also to increased analyte oxidation, possibly as a result of oxidative species formed electrochemically at the emitter electrode or in the gas - phase by discharge processes. These oxidative species are carried by the spray and impinge on and react with the sampled analyte during desorption/ionization. The relative abundance of oxidized species was more significant for analysis of deposited analyte having a relatively low surface concentration. Increasing spray solvent flow rate and addition of hydroquinone as a redox buffer to the spray solvent were found to decrease, but not entirely eliminate, analyte oxidation during analysis. The major parameters that both minimize and maximize analyte oxidation were identified and DESI-MS operational recommendations to avoid these unwanted reactions are suggested.

  4. Improved Imaging Resolution in Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Kertesz, Vilmos; Van Berkel, Gary J

    2008-01-01

    Imaging resolution of desorption electrospray ionization mass spectrometry (DESI-MS) was investigated using printed patterns on paper and thin-layer chromatography (TLC) plate surfaces. Resolution approaching 40 m was achieved with a typical DESI-MS setup, which is approximately 5 times better than the best resolution reported previously. This improvement was accomplished with careful control of operational parameters (particularly spray tip-to-surface distance, solvent flow rate, and spacing of lane scans). Also, an appropriately strong analyte/surface interaction and uniform surface texture on the size scale no larger that the desired imaging resolution were required to achieve this resolution. Overall, conditions providing the smallest possible effective desorption/ionization area in the DESI impact plume region and minimizing the analyte redistribution on the surface during analysis led to the improved DESI-MS imaging resolution.

  5. Laser desorption mass spectrometry for DNA analysis and sequencing

    SciTech Connect

    Chen, C.H.; Taranenko, N.I.; Tang, K.; Allman, S.L.

    1995-03-01

    Laser desorption mass spectrometry has been considered as a potential new method for fast DNA sequencing. Our approach is to use matrix-assisted laser desorption to produce parent ions of DNA segments and a time-of-flight mass spectrometer to identify the sizes of DNA segments. Thus, the approach is similar to gel electrophoresis sequencing using Sanger`s enzymatic method. However, gel, radioactive tagging, and dye labeling are not required. In addition, the sequencing process can possibly be finished within a few hundred microseconds instead of hours and days. In order to use mass spectrometry for fast DNA sequencing, the following three criteria need to be satisfied. They are (1) detection of large DNA segments, (2) sensitivity reaching the femtomole region, and (3) mass resolution good enough to separate DNA segments of a single nucleotide difference. It has been very difficult to detect large DNA segments by mass spectrometry before due to the fragile chemical properties of DNA and low detection sensitivity of DNA ions. We discovered several new matrices to increase the production of DNA ions. By innovative design of a mass spectrometer, we can increase the ion energy up to 45 KeV to enhance the detection sensitivity. Recently, we succeeded in detecting a DNA segment with 500 nucleotides. The sensitivity was 100 femtomole. Thus, we have fulfilled two key criteria for using mass spectrometry for fast DNA sequencing. The major effort in the near future is to improve the resolution. Different approaches are being pursued. When high resolution of mass spectrometry can be achieved and automation of sample preparation is developed, the sequencing speed to reach 500 megabases per year can be feasible.

  6. Helium concentration measurement in tungsten fuzz-like nanostructures by means of thermal desorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Gasparyan, Yu.; Efimov, V.; Bystrov, K.

    2016-05-01

    The concentration of helium in tungsten fuzz-like nanostructures has been measured by means of thermal desorption spectroscopy. Fuzz was formed on the W surface under intensive plasma irradiation at 1500 K. The helium content was measured first in the as-irradiated sample, and then in a similar sample with the fuzz mechanically scraped from the sample surface. The difference gave the He content in the fuzz, which was estimated to be He/ W  =  (13  ±  4)%.

  7. Laser desorption lamp ionization source for ion trap mass spectrometry.

    PubMed

    Wu, Qinghao; Zare, Richard N

    2015-01-01

    A two-step laser desorption lamp ionization source coupled to an ion trap mass spectrometer (LDLI-ITMS) has been constructed and characterized. The pulsed infrared (IR) output of an Nd:YAG laser (1064 nm) is directed to a target inside a chamber evacuated to ~15 Pa causing desorption of molecules from the target's surface. The desorbed molecules are ionized by a vacuum ultraviolet (VUV) lamp (filled with xenon, major wavelength at 148 nm). The resulting ions are stored and detected in a three-dimensional quadrupole ion trap modified from a Finnigan Mat LCQ mass spectrometer operated at a pressure of ≥ 0.004 Pa. The limit of detection for desorbed coronene molecules is 1.5 pmol, which is about two orders of magnitude more sensitive than laser desorption laser ionization mass spectrometry using a fluorine excimer laser (157 nm) as the ionization source. The mass spectrum of four standard aromatic compounds (pyrene, coronene, rubrene and 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (OPC)) shows that parent ions dominate. By increasing the infrared laser power, this instrument is capable of detecting inorganic compounds. PMID:25601688

  8. Rhodium Oxide Cluster Ions Studied by Thermal Desorption Spectrometry.

    PubMed

    Mafuné, Fumitaka; Takenouchi, Masato; Miyajima, Ken; Kudoh, Satoshi

    2016-01-28

    Gas-phase rhodium oxide clusters, RhnOm(+), were investigated by measuring the rate constants of oxidation and thermal desorption spectrometry. RhnOm(+) was suggested to be categorized into different states as m/n ≤ 1, 1 < m/n ≤ 1.5, and 1.5 < m/n in terms of energy and kinetics. For m/n ≤ 1, the O atoms readily adsorbed on the cluster with a large binding energy until RhO was formed. Under the O2-rich environment, oxidation proceeded until Rh2O3 was formed with a moderate binding energy. In addition, O2 molecules attached weakly to the cluster, and Rh2O3 formed RhnOm(+) (1.5 < m/n). The energetics and geometries of Rh6Om(+) (m = 6-12) were obtained using density functional theory calculations and were found to be consistent with the experimental results. PMID:26730616

  9. Laser Desorption Mass Spectrometry for DNA Sequencing and Analysis

    NASA Astrophysics Data System (ADS)

    Chen, C. H. Winston; Taranenko, N. I.; Golovlev, V. V.; Isola, N. R.; Allman, S. L.

    1998-03-01

    Rapid DNA sequencing and/or analysis is critically important for biomedical research. In the past, gel electrophoresis has been the primary tool to achieve DNA analysis and sequencing. However, gel electrophoresis is a time-consuming and labor-extensive process. Recently, we have developed and used laser desorption mass spectrometry (LDMS) to achieve sequencing of ss-DNA longer than 100 nucleotides. With LDMS, we succeeded in sequencing DNA in seconds instead of hours or days required by gel electrophoresis. In addition to sequencing, we also applied LDMS for the detection of DNA probes for hybridization LDMS was also used to detect short tandem repeats for forensic applications. Clinical applications for disease diagnosis such as cystic fibrosis caused by base deletion and point mutation have also been demonstrated. Experimental details will be presented in the meeting. abstract.

  10. Characterization of polymer decomposition products by laser desorption mass spectrometry

    NASA Technical Reports Server (NTRS)

    Pallix, Joan B.; Lincoln, Kenneth A.; Miglionico, Charles J.; Roybal, Robert E.; Stein, Charles; Shively, Jon H.

    1993-01-01

    Laser desorption mass spectrometry has been used to characterize the ash-like substances formed on the surfaces of polymer matrix composites (PMC's) during exposure on LDEF. In an effort to minimize fragmentation, material was removed from the sample surfaces by laser desorption and desorbed neutrals were ionized by electron impact. Ions were detected in a time-of-flight mass analyzer which allows the entire mass spectrum to be collected for each laser shot. The method is ideal for these studies because only a small amount of ash is available for analysis. Three sets of samples were studied including C/polysulfone, C/polyimide and C/phenolic. Each set contains leading and trailing edge LDEF samples and their respective controls. In each case, the mass spectrum of the ash shows a number of high mass peaks which can be assigned to fragments of the associated polymer. These high mass peaks are not observed in the spectra of the control samples. In general, the results indicate that the ash is formed from decomposition of the polymer matrix.

  11. Laser desorption mass spectrometry for point mutation detection

    SciTech Connect

    Taranenko, N.I.; Chung, C.N.; Zhu, Y.F.

    1996-12-31

    A point mutation can be associated with the pathogenesis of inherited or acquired diseases. Laser desorption mass spectrometry coupled with allele specific polymerase chain reaction (PCR) was first used for point mutation detection. G551D is one of several mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene present in 1-3% of the mutant CFTR alleles in most European populations. In this work, two different approaches were pursued to detect G551D point mutation in the cystic fibrosis gene. The strategy is to amplify the desired region of DNA template by PCR using two primers that overlap one base at the site of the point mutation and which vary in size. If the two primers based on the normal sequence match the target DNA sequence, a normal PCR product will be produced. However, if the alternately sized primers that match the mutant sequence recognize the target DNA, an abnormal PCR product will be produced. Thus, the mass spectrometer can be used to identify patients that are homozygous normal, heterozygous for a mutation or homozygous abnormal at a mutation site. Another approach to identify similar mutations is the use of sequence specific restriction enzymes which respond to changes in the DNA sequence. Mass spectrometry is used to detect the length of the restriction fragments by digestion of a PCR generated target fragment. 21 refs., 10 figs., 2 tabs.

  12. Laser desorption mass spectrometry for point mutation detection

    SciTech Connect

    Taranenko, N.I.; Chung, C.N.; Zhu, Y.F.

    1996-10-01

    A point mutation can be associated with the pathogenesis of inherited or acquired diseases. Laser desorption mass spectrometry coupled with allele specific polymerase chain reaction (PCR) was first used for point mutation detection. G551D is one of several mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene present in 1-3% of the mutant CFTR alleles in most European populations. In this work, two different approaches were pursued to detect G551D point mutation in the cystic fibrosis gene. The strategy is to amplify the desired region of DNA template by PCR using two primers that overlap one base at the site of the point mutation and which vary in size. If the two primers based on the normal sequence match the target DNA sequence, a normal PCR product will be produced. However, if the alternately sized primers that match the mutant sequence recognize the target DNA, an abnormal PCR product will be produced. Thus, the mass spectrometer can be used to identify patients that are homozygous normal, heterozygous for a mutation or homozygous abnormal at a mutation site. Another approach to identify similar mutations is the use of sequence specific restriction enzymes which respond to changes in the DNA sequence. Mass spectrometry is used to detect the length of the restriction fragments generated by digestion of a PCR generated target fragment. 21 refs., 10 figs., 2 tabs.

  13. Effects of alloying elements on thermal desorption of helium in Ni alloys

    NASA Astrophysics Data System (ADS)

    Xu, Q.; Cao, X. Z.; Sato, K.; Yoshiie, T.

    2012-12-01

    It is well known that the minor elements Si and Sn can suppress the formation of voids in Ni alloys. In the present study, to investigate the effects of Si and Sn on the retention of helium in Ni alloys, Ni, Ni-Si, and Ni-Sn alloys were irradiated by 5 keV He ions at 723 K. Thermal desorption spectroscopy (TDS) was performed at up to 1520 K, and microstructural observations were carried out to identify the helium trapping sites during the TDS analysis. Two peaks, at 1350 and 1457 K, appeared in the TDS spectrum of Ni. On the basis of the microstructural observations, the former peak was attributed to the release of trapped helium from small cavities and the latter to its release from large cavities. Small-cavity helium trapping sites were also found in the Ni-Si and Ni-Sn alloys, but no large cavities were observed in these alloys. In addition, it was found that the oversized element Sn could trap He atoms in the Ni-Sn alloy.

  14. Solvent jet desorption capillary photoionization-mass spectrometry.

    PubMed

    Haapala, Markus; Teppo, Jaakko; Ollikainen, Elisa; Kiiski, Iiro; Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

    2015-03-17

    A new ambient mass spectrometry method, solvent jet desorption capillary photoionization (DCPI), is described. The method uses a solvent jet generated by a coaxial nebulizer operated at ambient conditions with nitrogen as nebulizer gas. The solvent jet is directed onto a sample surface, from which analytes are extracted into the solvent and ejected from the surface in secondary droplets formed in collisions between the jet and the sample surface. The secondary droplets are directed into the heated capillary photoionization (CPI) device, where the droplets are vaporized and the gaseous analytes are ionized by 10 eV photons generated by a vacuum ultraviolet (VUV) krypton discharge lamp. As the CPI device is directly connected to the extended capillary inlet of the MS, high ion transfer efficiency to the vacuum of MS is achieved. The solvent jet DCPI provides several advantages: high sensitivity for nonpolar and polar compounds with limit of detection down to low fmol levels, capability of analyzing small and large molecules, and good spatial resolution (250 μm). Two ionization mechanisms are involved in DCPI: atmospheric pressure photoionization, capable of ionizing polar and nonpolar compounds, and solvent assisted inlet ionization capable of ionizing larger molecules like peptides. The feasibility of DCPI was successfully tested in the analysis of polar and nonpolar compounds in sage leaves and chili pepper. PMID:25715054

  15. Laser desorption mass spectrometry for fast DNA analysis

    SciTech Connect

    Chen, C.H.; Ch`ang, L.Y.; Taranenko, N.I.; Allman, S.L.; Tang, K.; Matteson, K.J.

    1995-09-01

    During the past few years, major effort has been directed toward developing mass spectrometry to measure biopolymers because of the great potential benefit to biomedical research. Hellenkamp and his co-workers were the first to report that large polypeptide molecules can be ionized and detected without significant fragmentation when a greater number of nicotinic acid molecules are used as a matrix. This method is now well known as matrix-assisted laser desorption/ionization (MALDI). Since then, various groups have reported measurements of very large proteins by MALDI. Reliable protein analysis by MALDI is more or less well established. However, the application of MALDI to nucleic acids analysis has been found to be much more difficult. Most research on the measurement of nucleic acid by MALDI were stimulated by the Human Genome Project. Up to now, the only method for reliable routine analysis of nucleic acid is gel electrophoresis. Different sizes of nucleic acids can be separated in gel medium when a high electric field is applied to the gel. However, the time needed to separate different sizes of DNA segments usually takes from several minutes to several hours. If MALDI can be successfully used for nucleic acids analysis, the analysis time can be reduced to less than I millisecond. In addition, no tagging with radioactive materials or chemical dyes is needed. In this work, we will review recent progress related to MALDI for DNA analysis.

  16. Imaging of Biological Tissues by Desorption Electrospray Ionization Mass Spectrometry

    PubMed Central

    Fernández, Facundo M.

    2013-01-01

    Mass spectrometry imaging (MSI) provides untargeted molecular information with the highest specificity and spatial resolution for investigating biological tissues at the hundreds to tens of microns scale. When performed under ambient conditions, sample pre-treatment becomes unnecessary, thus simplifying the protocol while maintaining the high quality of information obtained. Desorption electrospray ionization (DESI) is a spray-based ambient MSI technique that allows for the direct sampling of surfaces in the open air, even in vivo. When used with a software-controlled sample stage, the sample is rastered underneath the DESI ionization probe, and through the time domain, m/z information is correlated with the chemical species' spatial distribution. The fidelity of the DESI-MSI output depends on the source orientation and positioning with respect to the sample surface and mass spectrometer inlet. Herein, we review how to prepare tissue sections for DESI imaging and additional experimental conditions that directly affect image quality. Specifically, we describe the protocol for the imaging of rat brain tissue sections by DESI-MSI. PMID:23892773

  17. Desorption electrospray ionisation mass spectrometry and tandem mass spectrometry of low molecular weight synthetic polymers.

    PubMed

    Jackson, Anthony T; Williams, Jonathan P; Scrivens, James H

    2006-01-01

    A range of low molecular weight synthetic polymers has been characterised by means of desorption electrospray ionisation (DESI) combined with both mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Accurate mass experiments were used to aid the structural determination of some of the oligomeric materials. The polymers analysed were poly(ethylene glycol) (PEG), polypropylene glycol (PPG), poly(methyl methacrylate) (PMMA) and poly(alpha-methyl styrene). An application of the technique for characterisation of a polymer used as part of an active ingredient in a pharmaceutical tablet is described. The mass spectra and tandem mass spectra of all of the polymers were obtained in seconds, indicating the sensitivity of the technique. PMID:16912984

  18. Tunneling effects in the kinetics of helium and hydrogen isotopes desorption from single-walled carbon nanotube bundles

    SciTech Connect

    Danilchenko, B. A. Yaskovets, I. I.; Uvarova, I. Y.; Dolbin, A. V.; Esel'son, V. B.; Basnukaeva, R. M.; Vinnikov, N. A.

    2014-04-28

    The kinetics of desorption both helium isotopes and molecules of hydrogen and deuterium from open-ended or γ-irradiated single-walled carbon nanotube bundles was investigated in temperature range of 10–300 K. The gases desorption rates obey the Arrhenius law at high temperatures, deviate from it with temperature reduction and become constant at low temperatures. These results indicate the quantum nature of gas outflow from carbon nanotube bundles. We had deduced the crossover temperature below which the quantum corrections to the effective activation energy of desorption become significant. This temperature follows linear dependence against the inverse mass of gas molecule and is consistent with theoretical prediction.

  19. Ambient pressure laser desorption and laser-induced acoustic desorption ion mobility spectrometry detection of explosives.

    PubMed

    Ehlert, Sven; Walte, Andreas; Zimmermann, Ralf

    2013-11-19

    The development of fast, mobile, and sensitive detection systems for security-relevant substances is of enormous importance. Because of the low vapor pressures of explosives and improvised explosive devices, adequate sampling procedures are crucial. Ion mobility spectrometers (IMSs) are fast and sensitive instruments that are used as detection systems for explosives. Ambient pressure laser desorption (APLD) and ambient pressure laser-induced acoustic desorption (AP-LIAD) are new tools suitable to evaporate explosives in order to detect them in the vapor phase. Indeed, the most important advantage of APLD or AP-LIAD is the capability to sample directly from the surface of interest without any transfer of the analyte to other surfaces such as wipe pads. A much more gentle desorption, compared to classical thermal-based desorption, is possible with laser-based desorption using very short laser pulses. With this approach the analyte molecules are evaporated in a very fast process, comparable to a shock wave. The thermal intake is reduced considerably. The functionality of APLD and AP-LIAD techniques combined with a hand-held IMS system is shown for a wide range of common explosives such as EGDN (ethylene glycol dinitrate), urea nitrate, PETN (pentaerythritol tetranitrate), HMTD (hexamethylene triperoxide diamine), RDX (hexogen), tetryl (2,4,6-trinitrophenylmethylnitramine), and TNT (trinitrotoluene). Detection limits down to the low nanogram range are obtained. The successful combination of IMS detection and APLD/AP-LIAD sampling is shown. PMID:24116702

  20. Desorption Mass Spectrometry for Nonvolatile Compounds Using an Ultrasonic Cutter

    NASA Astrophysics Data System (ADS)

    Habib, Ahsan; Ninomiya, Satoshi; Chen, Lee Chuin; Usmanov, Dilshadbek T.; Hiraoka, Kenzo

    2014-07-01

    In this work, desorption of nonvolatile analytes induced by friction was studied. The nonvolatile compounds deposited on the perfluoroalkoxy substrate were gently touched by an ultrasonic cutter oscillating with a frequency of 40 kHz. The desorbed molecules were ionized by a dielectric barrier discharge (DBD) ion source. Efficient desorption of samples such as drugs, pharmaceuticals, amino acids, and explosives was observed. The limits of detection for these compounds were about 1 ng. Many compounds were detected in their protonated forms without undergoing significant fragmentation. When the DBD was off, no ions for the neutral samples could be detected, meaning that only desorption along with little ionization took place by the present technique.

  1. Sample-matrix effects in infrared laser neutral desorption, multiphoton-ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Beavis, R. C.; Lindner, J.; Grotemeyer, J.; Schlag, E. W.

    1988-05-01

    Sample-matrix effects in laser evaporation of intact neutral molecules (LEIM) prior to multiphoton ionization mass spectrometry (MUPI MS) are studied. The results show that a strong influence exists in adding matrix materials to the sample upon the desorption step. Using sugars as matrix leads to a suppression of pyrolysis products in small peptides by the laser desorption. As a result mass spectrometric signals due to the pyrolysis products are avoided.

  2. Speciation of arsenic oxides using laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Allen, T M; Bezabeh, D Z; Smith, C H; McCauley, E M; Jones, A D; Chang, D P; Kennedy, I M; Kelly, P B

    1996-11-15

    Positive and negative ion mass spectra of arsenic trioxide (As2O3) and arsenic pentaoxide (As2O5) have been obtained by single-step laser desorption/ionization time-of-flight mass spectrometry. Pulsed UV radiation at 266 nm was used for the simultaneous desorption and ionization of the solid sample. High-mass cluster ions that are unique to the oxidation state of each oxide sample appear in the negative ion mass spectra. The As2O3 produces As3O5-, while the As2O5 yields As3O8-. The formation of unique negative cluster ions presents the capability for arsenic oxidation state speciation by laser desorption/ionization mass spectrometry. The ability of time-of-flight mass spectrometry to examine the relative amounts of each arsenic oxide present in a series of mixtures is discussed. Application of our speciation technique to a model incinerator sample is demonstrated. PMID:8916457

  3. Ambient mass spectrometry imaging: plasma assisted laser desorption ionization mass spectrometry imaging and its applications.

    PubMed

    Feng, Baosheng; Zhang, Jialing; Chang, Cuilan; Li, Liping; Li, Min; Xiong, Xingchuang; Guo, Chengan; Tang, Fei; Bai, Yu; Liu, Huwei

    2014-05-01

    Mass spectrometry imaging (MSI) has been widely used in many research areas for the advantages of providing informative molecular distribution with high specificity. Among the recent progress, ambient MSI has attracted increasing interests owing to its characteristics of ambient, in situ, and nonpretreatment analysis. Here, we are presenting the ambient MSI for traditional Chinese medicines (TCMs) and authentication of work of art and documents using plasma assisted laser desorption ionization mass spectrometry (PALDI-MS). Compared with current ambient MSI methods, an excellent average resolution of 60 μm × 60 μm pixel size was achieved using this system. The feasibility of PALDI-based MSI was confirmed by seal imaging, and its authentication applications were demonstrated by imaging of printed Chinese characters. Imaging of the Radix Scutellariae slice showed that the two active components, baicalein and wogonin, mainly were distributed in the epidermis of the root, which proposed an approach for distinguishing TCMs' origins and the distribution of active components of TCMs and exploring the environmental effects of plant growth. PALDI-MS imaging provides a strong complement for the MSI strategy with the enhanced spatial resolution, which is promising in many research fields, such as artwork identification, TCMs' and botanic research, pharmaceutical applications, etc. PMID:24670045

  4. Spatially resolved thermal desorption/ionization coupled with mass spectrometry

    SciTech Connect

    Jesse, Stephen; Van Berkel, Gary J; Ovchinnikova, Olga S

    2013-02-26

    A system and method for sub-micron analysis of a chemical composition of a specimen are described. The method includes providing a specimen for evaluation and a thermal desorption probe, thermally desorbing an analyte from a target site of said specimen using the thermally active tip to form a gaseous analyte, ionizing the gaseous analyte to form an ionized analyte, and analyzing a chemical composition of the ionized analyte. The thermally desorbing step can include heating said thermally active tip to above 200.degree. C., and positioning the target site and the thermally active tip such that the heating step forms the gaseous analyte. The thermal desorption probe can include a thermally active tip extending from a cantilever body and an apex of the thermally active tip can have a radius of 250 nm or less.

  5. Surface-assisted laser desorption ionization mass spectrometry techniques for application in forensics.

    PubMed

    Guinan, Taryn; Kirkbride, Paul; Pigou, Paul E; Ronci, Maurizio; Kobus, Hilton; Voelcker, Nicolas H

    2015-01-01

    Matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) is an excellent analytical technique for the rapid and sensitive analysis of macromolecules (>700 Da), such as peptides, proteins, nucleic acids, and synthetic polymers. However, the detection of smaller organic molecules with masses below 700 Da using MALDI-MS is challenging due to the appearance of matrix adducts and matrix fragment peaks in the same spectral range. Recently, nanostructured substrates have been developed that facilitate matrix-free laser desorption ionization (LDI), contributing to an emerging analytical paradigm referred to as surface-assisted laser desorption ionization (SALDI) MS. Since SALDI enables the detection of small organic molecules, it is rapidly growing in popularity, including in the field of forensics. At the same time, SALDI also holds significant potential as a high throughput analytical tool in roadside, work place and athlete drug testing. In this review, we discuss recent advances in SALDI techniques such as desorption ionization on porous silicon (DIOS), nano-initiator mass spectrometry (NIMS) and nano assisted laser desorption ionization (NALDI™) and compare their strengths and weaknesses with particular focus on forensic applications. These include the detection of illicit drug molecules and their metabolites in biological matrices and small molecule detection from forensic samples including banknotes and fingerprints. Finally, the review highlights recent advances in mass spectrometry imaging (MSI) using SALDI techniques. PMID:24916100

  6. Rapid screening of pharmaceutical drugs using thermal desorption - SALDI mass spectrometry

    NASA Astrophysics Data System (ADS)

    Grechnikov, A. A.; Kubasov, A. E.; Georgieva, V. B.; Borodkov, A. S.; Nikiforov, S. M.; Simanovsky, Ya O.; Alimpiev, S. S.

    2012-12-01

    A novel approach to the rapid screening of pharmaceutical drugs by surface assisted laser desorption-ionization (SALDI) mass spectrometry with the rotating ball interface coupled with temperature programmed thermal desorption has been developed. Analytes were thermally desorbed and deposited onto the surface of amorphous silicon substrate attached to the rotating ball. The ball was rotated and the deposited analytes were analyzed using SALDI. The effectiveness of coupling SALDI mass spectrometry with thermal desorption was evaluated by the direct and rapid analysis of tablets containing lidocaine, diphenhydramine and propranolol without any sample pretreatment. The overall duration of the screening procedure was 30÷40 sec. Real urine samples were studied for drug analysis. It is shown that with simple preparation steps, urine samples can be quantitatively analyzed using the proposed technique with the detection limits in the range of 0.2÷0.5 ng/ml.

  7. The direct determination of HgS by thermal desorption coupled with atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Coufalík, Pavel; Zvěřina, Ondřej; Komárek, Josef

    2016-04-01

    This research was aimed at the direct determination of HgS in environmental samples by means of thermal desorption coupled with atomic absorption spectrometry. Operating parameters of the apparatus used for thermal desorption (including a prototype desorption unit) are described in this work, as well as the procedure for measuring mercury release curves together with an evaluation of the analytical signal including two methods of peak integration. The results of thermal desorption were compared with HgS contents obtained by sequential extraction. The limits of quantification of the proposed method for the selective determination of the black and red forms of HgS were 4 μg kg- 1 and 5 μg kg- 1, respectively. The limit of quantification of red HgS in soils was 35 μg kg- 1. The developed analytical procedure was applied to soil and sediment samples from historical mining areas.

  8. Laser Desorption Mass Spectrometry for High Throughput DNA Analysis and Its Applications

    SciTech Connect

    Allman, S.L.; Chen, C.H.; Golovlev, V.V.; Isola, N.R.; Matteson, K.J.; Potter, N.T.; Taranenko, N.I.

    1999-01-23

    Laser desorption mass spectrometry (LDMS) has been developed for DNA sequencing, disease diagnosis, and DNA Fingerprinting for forensic applications. With LDMS, the speed of DNA analysis can be much faster than conventional gel electrophoresis. No dye or radioactive tagging to DNA segments for detection is needed. LDMS is emerging as a new alternative technology for DNA analysis.

  9. Identification of Bacteria Using Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry

    ERIC Educational Resources Information Center

    Kedney, Mollie G.; Strunk, Kevin B.; Giaquinto, Lisa M.; Wagner, Jennifer A.; Pollack, Sidney; Patton, Walter A.

    2007-01-01

    Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS or simply MALDI) has become ubiquitous in the identification and analysis of biomacromolecules. As a technique that allows for the molecular weight determination of otherwise nonvolatile molecules, MALDI has had a profound impact in the molecular…

  10. Laser desorption mass spectrometry for high-throughput DNA analysis and its applications

    NASA Astrophysics Data System (ADS)

    Chen, C. H. Winston; Golovlev, Valeri V.; Taranenko, N. I.; Allman, S. L.; Isola, Narayana R.; Potter, N. T.; Matteson, K. J.; Chang, Linus Y.

    1999-05-01

    Laser desorption mass spectrometry (LDMS) has been developed for DNA sequencing, disease diagnosis, and DNA fingerprinting for forensic applications. With LDMS, the speed of DNA analysis can be much faster than conventional gel electrophoresis. No dye or radioactive tagging to DNA segments for detection is needed. LDMS is emerging as a new alternative technology for DNA analysis.

  11. The Effects of Added Hydrogen on Noble Gas Discharges Used as Ambient Desorption/Ionization Sources for Mass Spectrometry.

    PubMed

    Ellis, Wade C; Lewis, Charlotte R; Openshaw, Anna P; Farnsworth, Paul B

    2016-09-01

    We demonstrate the effectiveness of using hydrogen-doped argon as the support gas for the dielectric barrier discharge (DBD) ambient desorption/ionization (ADI) source in mass spectrometry. Also, we explore the chemistry responsible for the signal enhancement observed when using both hydrogen-doped argon and hydrogen-doped helium. The hydrogen-doped argon was tested for five analytes representing different classes of molecules. Addition of hydrogen to the argon plasma gas enhanced signals for gas-phase analytes and for analytes coated onto glass slides in positive and negative ion mode. The enhancements ranged from factors of 4 to 5 for gas-phase analytes and factors of 2 to 40 for coated slides. There was no significant increase in the background. The limit of detection for caffeine was lowered by a factor of 79 using H2/Ar and 2 using H2/He. Results are shown that help explain the fundamental differences between the pure-gas discharges and those that are hydrogen-doped for both argon and helium. Experiments with different discharge geometries and grounding schemes indicate that observed signal enhancements are strongly dependent on discharge configuration. Graphical Abstract ᅟ. PMID:27380389

  12. The Effects of Added Hydrogen on Noble Gas Discharges Used as Ambient Desorption/Ionization Sources for Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Ellis, Wade C.; Lewis, Charlotte R.; Openshaw, Anna P.; Farnsworth, Paul B.

    2016-07-01

    We demonstrate the effectiveness of using hydrogen-doped argon as the support gas for the dielectric barrier discharge (DBD) ambient desorption/ionization (ADI) source in mass spectrometry. Also, we explore the chemistry responsible for the signal enhancement observed when using both hydrogen-doped argon and hydrogen-doped helium. The hydrogen-doped argon was tested for five analytes representing different classes of molecules. Addition of hydrogen to the argon plasma gas enhanced signals for gas-phase analytes and for analytes coated onto glass slides in positive and negative ion mode. The enhancements ranged from factors of 4 to 5 for gas-phase analytes and factors of 2 to 40 for coated slides. There was no significant increase in the background. The limit of detection for caffeine was lowered by a factor of 79 using H2/Ar and 2 using H2/He. Results are shown that help explain the fundamental differences between the pure-gas discharges and those that are hydrogen-doped for both argon and helium. Experiments with different discharge geometries and grounding schemes indicate that observed signal enhancements are strongly dependent on discharge configuration.

  13. The Effects of Added Hydrogen on Noble Gas Discharges Used as Ambient Desorption/Ionization Sources for Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Ellis, Wade C.; Lewis, Charlotte R.; Openshaw, Anna P.; Farnsworth, Paul B.

    2016-09-01

    We demonstrate the effectiveness of using hydrogen-doped argon as the support gas for the dielectric barrier discharge (DBD) ambient desorption/ionization (ADI) source in mass spectrometry. Also, we explore the chemistry responsible for the signal enhancement observed when using both hydrogen-doped argon and hydrogen-doped helium. The hydrogen-doped argon was tested for five analytes representing different classes of molecules. Addition of hydrogen to the argon plasma gas enhanced signals for gas-phase analytes and for analytes coated onto glass slides in positive and negative ion mode. The enhancements ranged from factors of 4 to 5 for gas-phase analytes and factors of 2 to 40 for coated slides. There was no significant increase in the background. The limit of detection for caffeine was lowered by a factor of 79 using H2/Ar and 2 using H2/He. Results are shown that help explain the fundamental differences between the pure-gas discharges and those that are hydrogen-doped for both argon and helium. Experiments with different discharge geometries and grounding schemes indicate that observed signal enhancements are strongly dependent on discharge configuration.

  14. Determining fatty acids by desorption/ionization mass spectrometry using thin-layer chromatography substrates.

    PubMed

    Mirabelli, Mario F; Coviello, Giuseppe; Volmer, Dietrich A

    2015-06-01

    In this study, we demonstrate the application of ambient mass spectrometry for measuring fatty acids from various biological sample matrices such as olive oil, fish oil, salmon, and human serum. Optimum performance was obtained after spotting samples onto thin-layer chromatography (TLC) plates as sample substrates for a custom-built solvent-assisted desorption/ionization mass spectrometry (DI-MS) interface. Good to excellent linearities (coefficients of determination, 0.9856 to 0.9977) and reproducibilities (average 6 % relative standard deviation (RSD) using syringe deposition) were obtained after application of an internal standard. Signal suppression phenomena were minimized by separating the analytes by TLC to some extent prior to DI-MS, leading to a fourfold increase of signal-to-noise ratios as compared to single spot mixture analysis without TLC separation. Graphical Abstract Solvent-assisted desorption/ionization-mass spectrometry. PMID:25814272

  15. Multistage Reactive Transmission-Mode Desorption Electrospray Ionization Mass Spectrometry.

    PubMed

    Peters, Kevin C; Comi, Troy J; Perry, Richard H

    2015-09-01

    Elucidating reaction mechanisms is important for advancing many areas of science such as catalyst development. It is often difficult to probe fast reactions at ambient conditions with high temporal resolution. In addition, systems involving reagents that cross-react require analytical methods that can minimize interaction time and specify their order of introduction into the reacting system. Here, we explore the utility of transmission mode desorption electrospray ionization (TM-DESI) for reaction monitoring by directing a microdroplet spray towards a series of meshes with micrometer-sized openings coated with reagents, an approach we call multistage reactive TM-DESI (TM (n) -DESI, where n refers to the number of meshes; n = 2 in this report). Various stages of the reaction are initiated at each mesh surface, generating intermediates and products in microdroplet reaction vessels traveling towards the mass spectrometer. Using this method, we investigated the reactivity of iron porphyrin catalytic hydroxylation of propranolol and other substrates. Our experimental results indicate that TM (n) -DESI provides the ability to spatially separate reagents and control their order of introduction into the reacting system, thereby minimizing unwanted reactions that lead to catalyst deactivation and degradation products. In addition, comparison with DESI-MS analyses (the Zare and Latour laboratories published results suggesting accessible reaction times <1 ms) of the reduction of dichlorophenolindophenol by L-ascorbic acid suggest that TM (1) -DESI can access reaction times less than 1 ms. Multiple meshes allow sequential stages of desorption/ionization per MS scan, increasing the number of analytes and reactions that can be characterized in a single experiment. PMID:26091888

  16. Novel sampling methods for use with thermal desorption ion trap mass spectrometry

    SciTech Connect

    Barshick, S.A.; Buchanan, M.V.

    1994-12-31

    Novel sampling approaches have been investigated to improve the analytical utility of thermal desorption Direct Sampling Ion Trap Mass Spectrometry (DSITMS). Because DSITMS involves the direct introduction of samples into an ion trap mass spectrometer, problems with detection capabilities (sensitivity and selectivity) can often occur when performing trace analysis in complex matrices. Various sampling approaches have been evaluated to improve thermal desorption detection capabilities and to extend the utilities of DSITMS methodologies without significantly increasing analysis times or the cost-effectiveness of DSITMS methods. Three sampling approaches have been investigated including solid phase microextraction (SPME), solid phase extraction columns (SPEC), and purge and trap.

  17. Electrospray-assisted laser desorption/ionization mass spectrometry for direct ambient analysis of solids.

    PubMed

    Shiea, Jentaie; Huang, Min-Zon; Hsu, Hsiu-Jung; Lee, Chi-Yang; Yuan, Cheng-Hui; Beech, Iwona; Sunner, Jan

    2005-01-01

    A new method of electrospray-assisted laser desorption/ionization (ELDI) mass spectrometry, which combines laser desorption with post-ionization by electrospray, was applied to rapid analysis of solid materials under ambient conditions. Analytes were desorbed from solid metallic and insulating substrata using a pulsed nitrogen laser. Post-ionization produced high-quality mass spectra characteristic of electrospray, including protein multiple charging. For the first time, mass spectra of intact proteins were obtained using laser desorption without adding a matrix. Bovine cytochrome c and an illicit drug containing methaqualone were chosen in this study to demonstrate the applicability of ELDI to the analysis of proteins and synthetic organic compounds. PMID:16299699

  18. Study of the Thermal Decomposition of Some Components of Biomass by Desorption Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Palianytsia, Borys; Kulik, Tetiana; Dudik, Olesia; Cherniavska, Tetiana; Tonkha, Oksana

    The investigation of thermal transformations of lignin samples have been carried out using temperature programmed desorption mass spectrometry method (TPD-MS). Main stages and products of lignin pyrolysis have been identified. The first stages (Tmax = 230 °C and Tmax = 300 °C) are attributed to thermal transformations of lignin peripheral polysaccharide fragments such as hemicellulose and cellulose respectively. The second stage (Tmax = 335 °C) is associated with desorption of lignin structural elements in the molecular forms as a result of depolymerization processes of polymeric blocks of lignin. The third stage (Tmax = 370 °C) correspond to a deeper decomposition of lignin and characterized by desorption of smaller structural fragments in molecular forms (m/z = 110, pyrocatechol). Pressure-temperature curves of pyrolysis of lignin samples have been analyzed.

  19. Laser desorption with corona discharge ion mobility spectrometry for direct surface detection of explosives.

    PubMed

    Sabo, M; Malásková, M; Matejčík, S

    2014-10-21

    We present a new highly sensitive technique for the detection of explosives directly from the surface using laser desorption-corona discharge-ion mobility spectrometry (LD-CD-IMS). We have developed LD based on laser diode modules (LDM) and the technique was tested using three different LDM (445, 532 and 665 nm). The explosives were detected directly from the surface without any further preparation. We discuss the mechanism of the LD and the limitations of this technique such as desorption time, transport time and desorption area. After the evaluation of experimental data, we estimated the potential limits of detection of this method to be 0.6 pg for TNT, 2.8 pg for RDX and 8.4 pg for PETN. PMID:25118619

  20. Deblurring molecular images using desorption electrospray ionization mass spectrometry

    PubMed Central

    Parry, R. Mitchell; Galhena, Asiri S.; Fernandez, Facundo M.; Wang, May D.

    2016-01-01

    Traditional imaging techniques for studying the spatial distribution of biological molecules such as proteins, metabolites, and lipids, require the a priori selection of a handful of target molecules. Imaging mass spectrometry provides a means to analyze thousands of molecules at a time within a tissue sample, adding spatial detail to proteomic, metabolomic, and lipidomic studies. Compared to traditional microscopic images, mass spectrometric images have reduced spatial resolution and require a destructive acquisition process. In order to increase spatial detail, we propose a constrained acquisition path and signal degradation model enabling the use of a general image deblurring algorithm. Our analysis shows the potential of this approach and supports prior observations that the effect of the sprayer focuses on a central region much smaller than the extent of the spray. PMID:19963935

  1. Laser desorption fast gas chromatography-mass spectrometry in supersonic molecular beams.

    PubMed

    Shahar, T; Dagan, S; Amirav, A

    1998-06-01

    A novel method for fast analysis is presented. It is based on laser desorption injection followed by fast gas chromatography-mass spectrometry (GC-MS) in supersonic molecular beams. The sample was placed in an open air or purged laser desorption compartment, held at atmospheric pressure and near room temperature conditions. Desorption was performed with a XeCl Excimer pulsed laser with pulse energy of typically 3 mJ on the surface. About 20 pulses at 50 Hz were applied for sample injection, resulting in about 0.4 s injection time and one or a few micrograms sample vapor or small particles. The laser desorbed sample was further thermally vaporized at a heated frit glass filter located at the fast GC inlet. Ultrafast GC separation and quantification was achieved with a 50-cm-long megabore column operated with a high carrier gas flow rate of up to 240 mL/min. The high carrier gas flow rate provided effective and efficient entrainment of the laser desorbed species in the sweeping gas. Following the fast GC separation, the sample was analyzed by mass spectrometry in supersonic molecular beams. Both electron ionization and hyperthermal surface ionization were employed for enhanced selectivity and sensitivity. Typical laser desorption analysis time was under 10 s. The laser desorption fast GC-MS was studied and demonstrated with the following sample/matrices combinations, all without sample preparation or extraction: (a) traces of dioctylphthalate plasticizer oil on stainless steel surface and the efficiency of its cleaning; (b) the detection of methylparathion and aldicarb pesticides on orange leaves; (c) water surface analysis for the presence of methylparathion pesticide; (d) caffeine analysis in regular and decaffeinated coffee powder; (e) paracetamol and codeine drug analysis in pain relieving drug tablets; (f) caffeine trace analysis in raw urine; (g) blood analysis for the presence of 1 ppm lidocaine drug. The features and advantages of the laser desorption fast GC

  2. Laser desorption mass spectrometry: Technical limitations, fundamentals, and application to coal

    SciTech Connect

    Hunt, J.E.; Winans, R.E.

    1995-12-31

    Objective of this study is to assess scope and limitations of laser desorption (LD) and matrix-assisted laser desorption (MALDI) as applied to coals. LD and MALDI mass spectrometry are increasingly used to detect intact molecular species, such as proteins with masses from 1000 to 100,000 amu and beyond. MALDI is also being used for high molecular weight polymers. A good example, related to coal-type systems, is the report on lignin mass spectrometry by MALDI. The mass spectrum shows a wide molecular distribution of several hundred to larger than 16000, with the center of gravity of the distribution around 2600. Results are interpreted in terms of oligomeric lignin molecules. Thus, if there are indeed large molecular species in a polymeric content in coals or coal extracts, MALDI is an attractive technique.

  3. Recent progress in application of carbon nanomaterials in laser desorption/ionization mass spectrometry.

    PubMed

    Wang, Jing; Liu, Qian; Liang, Yong; Jiang, Guibin

    2016-04-01

    Carbon nanomaterials have attracted great interest over past decades owing to their unique physical properties, versatile functionalization chemistry, and biological compatibility. In this article, we review recent progress in application of carbon nanomaterials in laser desorption/ionization mass spectrometry (LDI MS). Various types of carbon nanomaterials, including fullerenes, carbon nanotubes, graphene, carbon nanodots, nanodiamond, nanofibers, nanohorns, and their derivative forms, are involved. The applications of these materials as new matrices or probes in matrix-assisted or surface-enhanced laser desorption/ionization mass spectrometry (MALDI or SELDI MS) are discussed. Finally, we summarize current challenges and give our perspectives on the future of applications of carbon nanomaterials in LDI MS. Graphical Abstract Carbon nanomaterials (e.g., fullerenes, carbon nanotubes, graphene, nanodiamond, etc.) can be used as novel matrices or probes in MALDI or SELDI MS. PMID:26753968

  4. Liquid Beam Ion Desorption Mass Spectrometry for Evaluating CASSINI Data

    NASA Astrophysics Data System (ADS)

    Stolz, Ferdinand; Reviol, Rene; Srama, Ralf; Trieloff, Mario; Postberg, Frank; Abel, Bernd

    2013-04-01

    Saturn's moon Enceladus emits plumes of ice particles from an area near its south pole which are detected and chemically analyzed by the Cosmic Dust Analyzer (CDA) on board the CASSINI spacecraft. Studying these ice particles provides unique insights into Enceladus geological properties. Technically the CDA is a time-of-flight mass spectrometer which delivers mass spectra of the particles and their fragments. Since interpretation of the available CDA data is particularly challenging we employ a laboratory experiment to imitate experimental conditions in space. Key part of our experimental setup is a micron-sized water beam in high vacuum. This beam is rapidly heated up by an infrared laser pulse, which is tuned to excite the OH-stretch vibration of water molecules. This causes the water beam to dissipate into small droplets, some of which carry a net charge even though the laser energy is well below the molecular ionisation energy. The charged droplets are then analyzed in a time-of-flight mass spectrometer. With this experimental setup we successfully simulated the space born ice particles measured at Enceladus. By varying the laser intensity in our experiments, we can vary the amount of energy deposited in the liquid beam, and thus model different particle velocities. Also, variation of solute concentration in the water beam provides valuable information about ice particle composition. Some examples for anorganic solutes studied so far are sodium chloride, ammonia and hydrogen sulfite. A special feature of our experimental technique is that desorption of particles from the liquid beam is particularly soft. This is explained by the fact that all laser energy is absorbed by the water molecules. In this way molecular bonds of solutes stay intact and molecular solutes are transferred into the droplet phase without getting destroyed. This is particularly interesting in the context of analyzing organic compounds - some of which have been detected at Enceladus. Using

  5. The Need for Speed in Matrix-Assisted Laser Desorption/Ionization Imaging Mass Spectrometry

    PubMed Central

    Prentice, Boone M.; Caprioli, Richard M.

    2016-01-01

    Imaging mass spectrometry (IMS) has emerged as a powerful analytical tool enabling the direct molecular mapping of many types of tissue. Specifically, matrix-assisted laser desorption/ ionization (MALDI) represents one of the most broadly applicable IMS technologies. In recent years, advances in solid state laser technology, mass spectrometry instrumentation, computer technology, and experimental methodology have produced IMS systems capable of unprecedented data acquisition speeds (>50 pixels/second). In applications of this technology, throughput is an important consideration when designing an IMS experiment. As IMS becomes more widely adopted, continual improvements in experimental setups will be important to address biologically and clinically relevant time scales.

  6. Fragmentation of HCN in optically selected mass spectrometry: Nonthermal ion cooling in helium nanodroplets

    SciTech Connect

    Lewis, William K.; Bemish, Raymond J.; Miller, Roger E.

    2005-10-08

    A technique that combines infrared laser spectroscopy and helium nanodroplet mass spectrometry, which we refer to as optically selected mass spectrometry, is used to study the efficiency of ion cooling in helium. Electron-impact ionization is used to form He{sup +} ions within the droplets, which go on to transfer their charge to the HCN dopant molecules. Depending upon the droplet size, the newly formed ion either fragments or is cooled by the helium before fragmentation can occur. Comparisons with gas-phase fragmentation data suggest that the cooling provided by the helium is highly nonthermal. An 'explosive' model is proposed for the cooling process, given that the initially hot ion is embedded in such a cold solvent.

  7. Brominated Tyrosine and Polyelectrolyte Multilayer Analysis by Laser Desorption VUV Postionization and Secondary Ion Mass Spectrometry

    SciTech Connect

    University of Illinois at Chicago; Blaze, Melvin M. T.; Takahashi, Lynelle; Zhou, Jia; Ahmed, Musahid; Gasper, Gerald; Pleticha, F. Douglas; Hanley, Luke

    2011-03-14

    The small molecular analyte 3,5-dibromotyrosine (Br2Y) and chitosan-alginate polyelectrolyte multilayers (PEM) with and without adsorbed Br2Y were analyzed by laser desorption postionization mass spectrometry (LDPI-MS). LDPI-MS using 7.87 eV laser and tunable 8 ? 12.5 eV synchrotron vacuum ultraviolet (VUV) radiation found that desorption of clusters from Br2Y films allowed detection by≤8 eV single photon ionization. Thermal desorption and electronic structure calculations determined the ionization energy of Br2Y to be ~;;8.3?0.1 eV and further indicated that the lower ionization energies of clusters permitted their detection at≤8 eV photon energies. However, single photon ionization could only detect Br2Y adsorbed within PEMs when using either higher photon energies or matrix addition to the sample. All samples were also analyzed by 25 keV Bi3 + secondary ion mass spectrometry (SIMS), with the negative ion spectra showing strong parent ion signal which complemented that observed by LDPI-MS. The negative ion SIMS depended strongly on the high electron affinity of this specific analyte and the analyte?s condensed phase environment.

  8. Brominated Tyrosine and Polyelectrolyte Multilayer Analysis by Laser Desorption VUV Postionization and Secondary Ion Mass Spectrometry

    PubMed Central

    Melvin Blaze, M.T.; Takahashi, Lynelle K.; Zhou, Jia; Ahmed, Musahid; Gasper, Gerald L.; Pleticha, F. Douglas; Hanley, Luke

    2011-01-01

    The small molecular analyte 3,5-dibromotyrosine (Br2Y) and chitosan-alginate polyelectrolyte multilayers (PEM) with and without adsorbed Br2Y were analyzed by laser desorption postionization mass spectrometry (LDPI-MS). LDPI-MS using 7.87 eV laser and tunable 8 – 12.5 eV synchrotron vacuum ultraviolet (VUV) radiation found that desorption of clusters from Br2Y films allowed detection by ≤8 eV single photon ionization. Thermal desorption and electronic structure calculations determined the ionization energy of Br2Y to be ~8.3±0.1 eV and further indicated that the lower ionization energies of clusters permitted their detection at ≤8 eV photon energies. However, single photon ionization could only detect Br2Y adsorbed within PEMs when using either higher photon energies or matrix addition to the sample. All samples were also analyzed by 25 keV Bi3+ secondary ion mass spectrometry (SIMS), with the negative ion spectra showing strong parent ion signal which complemented that observed by LDPI-MS. However, the negative ion SIMS appeared strongly dependent on the high electron affinity of this specific analyte and the analyte’s condensed phase environment. PMID:21548612

  9. Matrix-assisted laser desorption fourier transform mass spectrometry for biological compounds

    SciTech Connect

    Hettich, R.; Buchanan, M.

    1990-01-01

    The recent development of matrix-assisted UV laser desorption (LD) mass spectrometry has made possible the ionization and detection of extremely large molecules (with molecular weights exceeding 100,000 Daltons). This technique has generated enormous interest in the biological community for the direct examination of large peptides and oligonucleotides. Although this matrix-assisted ionization method has been developed and used almost exclusively with time-of-flight (TOF) mass spectrometers, research is currently in progress to demonstrate this technique with trapped ion mass spectrometers, such as Fourier transform ion cyclotron resonance mass spectrometry (FTMS). The potential capabilities of FTMS for wide mass range, high resolution measurement, and ion trapping experiments suggest that this instrumental technique should be useful for the detailed structural characterization of large ions generated by the matrix-assisted technique. We have recently demonstrated that matrix-assisted ultraviolet laser desorption can be successfully used with FTMS for the ionization of small peptides. The objective of this report is to summarize the application and current limitations of matrix-assisted laser desorption FTMS for the characterization of peptides and oligonucleotides at the isomeric level. 4 refs., 3 figs., 2 tabs.

  10. Comparison of Three Plasma Sources for Ambient Desorption/Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    McKay, Kirsty; Salter, Tara L.; Bowfield, Andrew; Walsh, James L.; Gilmore, Ian S.; Bradley, James W.

    2014-09-01

    Plasma-based desorption/ionization sources are an important ionization technique for ambient surface analysis mass spectrometry. In this paper, we compare and contrast three competing plasma based desorption/ionization sources: a radio-frequency (rf) plasma needle, a dielectric barrier plasma jet, and a low-temperature plasma probe. The ambient composition of the three sources and their effectiveness at analyzing a range of pharmaceuticals and polymers were assessed. Results show that the background mass spectrum of each source was dominated by air species, with the rf needle producing a richer ion spectrum consisting mainly of ionized water clusters. It was also seen that each source produced different ion fragments of the analytes under investigation: this is thought to be due to different substrate heating, different ion transport mechanisms, and different electric field orientations. The rf needle was found to fragment the analytes least and as a result it was able to detect larger polymer ions than the other sources.

  11. Development of Laser Desorption Imaging Mass Spectrometry Methods to Investigate the Molecular Composition of Latent Fingermarks

    NASA Astrophysics Data System (ADS)

    Lauzon, Nidia; Dufresne, Martin; Chauhan, Vinita; Chaurand, Pierre

    2015-06-01

    For a century, fingermark analysis has been one of the most important and common methods in forensic investigations. Modern chemical analysis technologies have added the potential to determine the molecular composition of fingermarks and possibly identify chemicals a suspect may have come into contact with. Improvements in analytical detection of the molecular composition of fingermarks is therefore of great importance. In this regard, matrix-assisted laser desorption ionization (MALDI) and laser desorption ionization (LDI) imaging mass spectrometry (IMS) have proven to be useful technologies for fingermark analysis. In these analyses, the choice of ionizing agent and its mode of deposition are critical steps for the identification of molecular markers. Here we propose two novel and complementary IMS approaches for endogenous and exogenous substance detection in fingermarks: sublimation of 2-mercaptobenzothiazol (2-MBT) matrix and silver sputtering.

  12. Fossil fuel characterization using laser desorption mass spectrometry: Applications and limitations

    SciTech Connect

    Hunt, J.E.; Winans, R.E.

    1995-08-01

    Laser desorption mass spectroscopy (LDMS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI) are applicable to the high molecular weight compounds in fossil fuels which resist intact ionization. LD or MALDI of coals and extracts do not show reproducible ion intensity over mass 2000. This paper describes the scope and limitations of LD and MALD in time-of-flight mass spectrometers applied to high molecular weight molecules such as proteins and polymers. Coal was also analyzed. It is concluded that the sample preparation step is perhaps the most important part in MALDI. Observed high mass ions in coal may be from contaminant proteins. Optimal matrices must be found. Finally, the mass spectrum is senstive to number average molecular weight; a low value, however, does not preclude presence of high molecular weight species.

  13. Development of laser desorption imaging mass spectrometry methods to investigate the molecular composition of latent fingermarks.

    PubMed

    Lauzon, Nidia; Dufresne, Martin; Chauhan, Vinita; Chaurand, Pierre

    2015-06-01

    For a century, fingermark analysis has been one of the most important and common methods in forensic investigations. Modern chemical analysis technologies have added the potential to determine the molecular composition of fingermarks and possibly identify chemicals a suspect may have come into contact with. Improvements in analytical detection of the molecular composition of fingermarks is therefore of great importance. In this regard, matrix-assisted laser desorption ionization (MALDI) and laser desorption ionization (LDI) imaging mass spectrometry (IMS) have proven to be useful technologies for fingermark analysis. In these analyses, the choice of ionizing agent and its mode of deposition are critical steps for the identification of molecular markers. Here we propose two novel and complementary IMS approaches for endogenous and exogenous substance detection in fingermarks: sublimation of 2-mercaptobenzothiazol (2-MBT) matrix and silver sputtering. PMID:25846823

  14. Infrared matrix-assisted laser desorption electrospray ionization mass spectrometry imaging analysis of biospecimens.

    PubMed

    Bokhart, M T; Muddiman, D C

    2016-09-21

    Infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) mass spectrometry imaging (MSI) is a technique well suited for analysis of biological specimens. This tutorial review focuses on recent advancements and applications of IR-MALDESI MSI to better understand key biological questions. Through optimization of user-defined source parameters, comprehensive and quantitative MSI data can be obtained for a variety of analytes. The effect of an ice matrix layer is well defined in the context of desorption dynamics and resulting ion abundance. Optimized parameters and careful control of conditions affords quantitative MSI data which provides valuable information for targeted, label-free drug distribution studies and untargeted metabolomic datasets. Challenges and limitations of MSI using IR-MALDESI are addressed in the context of the bioimaging field. PMID:27484166

  15. Silica-fiber microextraction for laser desorption ion trap mass spectrometry

    SciTech Connect

    Cisper, M.E.; Earl, W.L.; Nogar, N.S.; Hemberger, P.H. )

    1994-06-01

    We have coupled sample collection by solid-phase microextraction on disposable fused silica optical fibers with analysis by laser desorption ion trap mass spectrometry for rapid screening of organic contaminants in complex matrices. Because the silica-fiber probe serves as both the sampling medium and the sample support for laser desorption, traditional methods of sample preparation are eliminated with the expected gains in speed and simplicity. Pyrene was the benchmark compound in these experiments but we show that the technique is also applicable to other polycyclic aromatic hydrocarbons (PAHs) and semivolatile compounds, laser dyes, pesticides, and peptides. Derivatizing the silica fiber improves the analyte collection efficiency, and firing the laser during a ring electrode rf ramp promotes dependable trapping of laser-desorbed ions. 32 refs., 5 figs.

  16. The Application of Ultrafast Laser Pulses to Laser Desorption Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Cui, Yang

    Ultrashort femtosecond laser pulses display exceptional performance for the selective ablation of materials, includes metals, semiconductors, and biological tissues. They do not damage the remaining unablated portion of a sample, which permits the possibility of depth profiling by repeat sampling at the same location. With sufficiently micro-focused fs laser pulse length beam, high lateral resolution mass spectrometry imaging is possible, while sample damage may degrade ultimate lateral resolution in some other methods. Combining imaging and depth profiling could ultimately leads to tomographical mass spectrometry or 3D imaging MS. Laser postionization, a "soft" ionization method, was combined with ultrafast laser desorption for enhanced molecular analysis. A customized femtosecond laser desorption/ablation postionization time-of-flight mass spectrometer was designed and built. The construction and performance of both phases including the VUV source are detailed. Instrument control software was written to operate this instrument, and many automated experiments were successfully demonstrated by this software. Elemental and molecular analysis was carried out on the instrument and demonstrated exceptional performance for fs laser pulse sampling of small areas. Studies demonstrated the imaging and depth profiling capability of fs-LDPI on metals, semiconductors and intact biofilm tissues. Attempts were made to reach the limit of lateral resolution of imaging by fs-LDPI-MS. The results showed similar lateral resolution of <2 mum for both fs 800 nm and 400 nm desorption beams. To improve the repetition rate for high speed imaging application, an alternative LDPI scheme was designed and constructed. The fs 800 beam was tripled to 267 nm and delivered into the ion source as an ionization laser, while a ns 349 nm pulse laser was used for desorption. Preliminary data showed certain intact molecular ions can be detected. Fragmentation tendency was measured against various

  17. Identification of Fatty Acids, Phospholipids, and Their Oxidation Products Using Matrix-Assisted Laser Desorption Ionization Mass Spectrometry and Electrospray Ionization Mass Spectrometry

    ERIC Educational Resources Information Center

    Harmon, Christopher W.; Mang, Stephen A.; Greaves, John; Finlayson-Pitts, Barbara J.

    2010-01-01

    Electrospray ionization mass spectrometry (ESI-MS) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) have found increasing application in the analysis of biological samples. Using these techniques to solve problems in analytical chemistry should be an essential component of the training of undergraduate chemists. We…

  18. Laser desorption and matrix-assisted laser desorption/ionization mass spectrometry of 29-kDa Au:SR cluster compounds.

    PubMed

    Schaaff, T Gregory

    2004-11-01

    Positive and negative ions generated by laser-based ionization methods from three gold:thiolate cluster compounds are mass analyzed by time-of-flight mass spectrometry. The three compounds have similar inorganic core masses ( approximately 29 kDa, approximately 145 Au atoms) but different n-alkanethiolate ligands associated with each cluster compound (Au:SR, R = butane, hexane, dodecane). Irradiation of neat films (laser desorption/ionization) and films generated by dilution of the cluster compounds in an organic acid matrix (matrix-assisted laser desorption/ionization) with a nitrogen laser (337 nm) produced distinct ion abundances that are relevant to different structural aspects of the cluster compound. Laser desorption/ionization of neat Au:SR compound films produces ions consistent with the inorganic core mass (i.e., devoid of original hydrocarbon content). Matrix-assisted laser desorption/ionization produces either ions with m/z values consistent with the core mass of the cluster compounds or ions with m/z values consistent with the approximate molecular weight of the cluster compounds, depending on ionization conditions. The ion abundances, and ionization conditions under which they are detected, provide insight into desorption/ionization processes for these unique cluster compounds as well as other analytes typically studied by matrix-assisted laser desorption/ionization. PMID:15516109

  19. Analysis of sexual assault evidence by desorption electrospray ionization mass spectrometry.

    PubMed

    Mirabelli, Mario F; Chramow, Alexander; Cabral, Elaine C; Ifa, Demian R

    2013-07-01

    Desorption electrospray ionization mass spectrometry (DESI-MS) is employed in the forensic analysis of chemical components present in condoms and imaging of latent fingerprints as circumstantial evidence of sexual assault. Polymers such as nonoxynol-9, polyethylene glycol, and polydimethylsiloxane, as well as small molecules additives such as N-methylmorpholine, N-octylamine, N,N-dibutyl formamide, and isonox 132, commonly used in lubricated condom formulations, were successfully characterized by DESI. The results suggest that DESI-MS is useful for identification of this type of evidence, and it has advantages over conventional extractive techniques, in terms of speed of analysis and ease of use. PMID:23832933

  20. Desorption Electrospray Ionization Mass Spectrometry for Lipid Characterization and Biological Tissue Imaging

    PubMed Central

    Eberlin, Livia S.; Ferreira, Christina R.; Dill, Allison L.; Ifa, Demian R.; Cooks, R. Graham

    2011-01-01

    Desorption electrospray ionization mass spectrometry (DESI-MS) imaging of biological samples allows untargeted analysis and structural characterization of lipids ionized from the near-surface region of a sample under ambient conditions. DESI is a powerful and sensitive MS ionization method for 2D and 3D imaging of lipids from direct and unmodified complex biological samples. This review describes the strengths and limitations of DESI-MS for lipid characterization and imaging together with the technical workflow and a survey of applications. Included are discussions of lipid mapping and biomarker discovery as well as a perspective on the future of DESI imaging. PMID:21645635

  1. Molecular Weight Determinations of Proteins by Californium Plasma Desorption Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Sundqvist, B.; Roepstorff, Peter; Fohlman, J.; Hedin, A.; Hakansson, P.; Kamensky, I.; Lindberg, M.; Salehpour, M.; Sawe, G.

    1984-11-01

    The plasma desorption mass spectrometry method is used to determine the molecular weights of larger molecules than before, to determine the molecular weights of proteins and peptides in mixtures, and to monitor protein modification reactions. Proteins up to molecular weight 25,000 can now be studied with a mass spectrometric technique. Protein-peptide mixtures that could not be resolved with conventional techniques were successfully analyzed by this technique. The precision of the method is good enough to permit one to follow the different steps in the conversion of porcine insulin to human insulin.

  2. Forensic applications of desorption electrospray ionisation mass spectrometry (DESI-MS).

    PubMed

    Morelato, Marie; Beavis, Alison; Kirkbride, Paul; Roux, Claude

    2013-03-10

    Desorption electrospray ionisation mass spectrometry (DESI-MS) is an emerging analytical technique that enables in situ mass spectrometric analysis of specimens under ambient conditions. It has been successfully applied to a large range of forensically relevant materials. This review assesses and highlights forensic applications of DESI-MS including the analysis and detection of illicit drugs, explosives, chemical warfare agents, inks and documents, fingermarks, gunshot residues and drugs of abuse in urine and plasma specimens. The minimal specimen preparation required for analysis and the sensitivity of detection achieved offer great advantages, especially in the field of forensic science. PMID:23498998

  3. Exploring the high-mass components of humic acid by laser desorption ionization mass spectrometry.

    PubMed

    Chilom, Gabriela; Chilom, Ovidiu; Rice, James A

    2008-05-01

    Leonardite and Elliot soil humic acids have been analyzed by laser desorption ionization mass spectrometry (LDI MS) in the m/z 4000-200,000 range. Positive ion mass spectra for each humic acid obtained under optimum conditions showed a broad high-mass distribution between m/z 20,000 and 80,000. The dependence of the mass distribution on instrumental parameters and solution conditions was used to investigate the nature of the high-mass peaks from humic acid spectra. Our data suggests that macromolecular ions and humic acid aggregates have the same probability of occurrence while cluster ion formation has a low probability of occurrence. PMID:18421699

  4. Identification of fleeting electrochemical reaction intermediates using desorption electrospray ionization mass spectrometry.

    PubMed

    Brown, Timothy A; Chen, Hao; Zare, Richard N

    2015-06-17

    We report a new method for the mass spectrometric detection of fleeting reaction intermediates in electrochemical reactions utilizing a "waterwheel" working electrode setup. This setup takes inspiration from desorption electrospray ionization (DESI) mass spectrometry, where the sampling time is on the order of milliseconds, to sample directly from the surface of a working electrode for mass spectrometric analysis. We present data that show the formation of a diimine intermediate of the electrochemical oxidation of uric acid that has a lifetime in solution of 23 ms as well as data that provide evidence for the formation of a similar diimine species from the electrooxidation of xanthine, which has not been previously observed. PMID:26030136

  5. Fast Differential Analysis of Propolis Using Surface Desorption Atmospheric Pressure Chemical Ionization Mass Spectrometry

    PubMed Central

    Huang, Xue-yong; Guo, Xia-li; Luo, Huo-lin; Fang, Xiao-wei; Zhu, Teng-gao; Zhang, Xing-lei; Chen, Huan-wen; Luo, Li-ping

    2015-01-01

    Mass spectral fingerprints of 24 raw propolis samples, including 23 from China and one from the United States, were directly obtained using surface desorption atmospheric pressure chemical ionization mass spectrometry (SDAPCI-MS) without sample pretreatment. Under the optimized experimental conditions, the most abundant signals were detected in the mass ranges of 70 to 500 m/z and 200 to 350 m/z, respectively. Principal component analyses (PCA) for the two mass ranges showed similarities in that the colors had a significant correlation with the first two PCs; in contrast there was no correlation with the climatic zones from which the samples originated. Analytes such as chrysin, pinocembrin, and quercetin were detected and identified using multiple stage mass spectrometry within 3 min. Therefore, SDAPCI-MS can be used for rapid and reliable high-throughput analysis of propolis. PMID:26339245

  6. Laser Desorption Ionization Mass Spectrometry Imaging of Drosophila Brain Using Matrix Sublimation versus Modification with Nanoparticles.

    PubMed

    Phan, Nhu T N; Mohammadi, Amir Saeid; Dowlatshahi Pour, Masoumeh; Ewing, Andrew G

    2016-02-01

    Laser desorption ionization mass spectrometry (LDI-MS) is used to image brain lipids in the fruit fly, Drosophila, a common invertebrate model organism in biological and neurological studies. Three different sample preparation methods, including sublimation with two common organic matrixes for matrix-assisted laser desorption ionization (MALDI) and surface-assisted laser desorption ionization (SALDI) using gold nanoparticles, are examined for sample profiling and imaging the fly brain. Recrystallization with trifluoroacetic acid following matrix deposition in MALDI is shown to increase the incorporation of biomolecules with one matrix, resulting in more efficient ionization, but not for the other matrix. The key finding here is that the mass fragments observed for the fly brain slices with different surface modifications are significantly different. Thus, these approaches can be combined to provide complementary analysis of chemical composition, particularly for the small metabolites, diacylglycerides, phosphatidylcholines, and triacylglycerides, in the fly brain. Furthermore, imaging appears to be beneficial using modification with gold nanoparticles in place of matrix in this application showing its potential for cellular and subcellular imaging. The imaging protocol developed here with both MALDI and SALDI provides the best and most diverse lipid chemical images of the fly brain to date with LDI. PMID:26705612

  7. Pyroelectricity Assisted Infrared-Laser Desorption Ionization (PAI-LDI) for Atmospheric Pressure Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Li, Yanyan; Ma, Xiaoxiao; Wei, Zhenwei; Gong, Xiaoyun; Yang, Chengdui; Zhang, Sichun; Zhang, Xinrong

    2015-08-01

    A new atmospheric pressure ionization method termed pyroelectricity-assisted infrared laser desorption ionization (PAI-LDI) was developed in this study. The pyroelectric material served as both sample target plate and enhancing ionization substrate, and an IR laser with wavelength of 1064 nm was employed to realize direct desorption and ionization of the analytes. The mass spectra of various compounds obtained on pyroelectric material were compared with those of other substrates. For the five standard substances tested in this work, LiNbO3 substrate produced the highest ion yield and the signal intensity was about 10 times higher than that when copper was used as substrate. For 1-adamantylamine, as low as 20 pg (132.2 fmol) was successfully detected. The active ingredient in (Compound Paracetamol and 1-Adamantylamine Hydrochloride Capsules), 1-adamantylamine, can be sensitively detected at an amount as low as 150 pg, when the medicine stock solution was diluted with urine. Monosaccharide and oligosaccharides in Allium Cepa L. juice was also successfully identified with PAI-LDI. The method did not require matrix-assisted external high voltage or other extra facility-assisted set-ups for desorption/ionization. This study suggested exciting application prospect of pyroelectric materials in matrix- and electricity-free atmospheric pressure mass spectrometry research.

  8. Heavy resid asphaltene characterization using high resolution and laser desorption mass spectrometry

    SciTech Connect

    Hunt, J.E.; Kim, Y.; Winans, R.E.

    1995-12-31

    Resid is the nondistillable portion of crude oil, generally thought to consist largely of unsaturated molecules of considerable size and ring number. Such molecules must be upgraded to more saturated compounds if they are to be used as fuel sources. Current processing of resid is performed though coking, thermal and catalytic cracking, deasphalting and hydroprocessing. Thermal treatments, however, produce large quantities of low-value coke and hydroprocessing is expensive. Asphaltenes comprise the most process resistant portion of the resid. They contain high concentrations of heteroatoms and a high degree of unsaturation. Because these undesirable characteristics are concentrated in asphaltenes, finding an improved method of upgrading asphaltenes is a prerequisite to improving the upgrading of whole resid to viable fuel. Asphaltenes have, at present, only an operational definition. They are insoluble in straight chain saturated hydrocarbons. Very little is known about the structure of compounds in asphaltenes. They are a highly diverse group of compounds that are resistant to analysis by conventional methods. Conclusions about the structures of asphaltenes tends to be speculative. In this study desorption electron impact (HREIMS), chemical ionization high resolution mass spectrometry (HRCIMS), and laser desorption mass spectrometry (LD) have been applied to deasphalted oils (DAO) and asphaltenes derived from heavy Maya resid. LD data should yield information on the high molecular weight aromatic compounds, while HRMS can provide molecular characterization.

  9. Laser desorption/ionization mass spectrometry of lipids using etched silver substrates.

    PubMed

    Schnapp, Andreas; Niehoff, Ann-Christin; Koch, Annika; Dreisewerd, Klaus

    2016-07-15

    Silver-assisted laser desorption/ionization mass spectrometry can be used for the analysis of small molecules. For example, adduct formation with silver cations enables the molecular analysis of long-chain hydrocarbons, which are difficult to ionize via conventional matrix-assisted laser desorption ionization (MALDI). Here we used highly porous silver foils, produced by etching with nitric acid, as sample substrates for LDI mass spectrometry. As model system for the analysis of complex lipid mixtures, cuticular extracts of fruit flies (Drosophila melanogaster) and worker bees (Apis mellifera) were investigated. The mass spectra obtained by spotting extract onto the etched silver substrates demonstrate the sensitive detection of numerous lipid classes such as long-chain saturated and unsaturated hydrocarbons, fatty acyl alcohols, wax esters, and triacylglycerols. MS imaging of cuticular surfaces with a lateral resolution of a few tens of micrometers became possible after blotting, i.e., after transferring lipids by physical contact with the substrate. The examples of pheromone-producing male hindwings of the squinting bush brown butterfly (Bicyclus anynana) and a fingermark are shown. Because the substrates are also easy to produce, they provide a viable alternative to colloidal silver nanoparticles and other so far described silver substrates. PMID:26827933

  10. Molecular Surface Sampling and Chemical Imaging using Proximal Probe Thermal Desorption/Secondary Ionization Mass Spectrometry

    SciTech Connect

    Ovchinnikova, Olga S; Kertesz, Vilmos; Van Berkel, Gary J

    2011-01-01

    Proximal probe thermal desorption/secondary ionization mass spectrometry was studied and applied to molecular surface sampling and chemical imaging using printed patterns on photopaper as test substrates. With the use of a circular cross section proximal probe with a tip diameter of 50 m and fixed temperature (350 C), the influence of probe-to-surface distance, lane scan spacing, and surface scan speed on signal quality and spatial resolution were studied and optimized. As a compromise between signal amplitude, signal reproducibility, and data acquisition time, a surface scan speed of 100 m/s, probe-to-paper surface distance of 5 m, and lane spacing of 10 m were used for imaging. Under those conditions the proximal probe thermal desorption/secondary ionization mass spectrometry method was able to achieve a spatial resolution of about 50 m as determined by the ability to distinguish surface patterns of known dimensions that were printed on the paper substrate. It is expected that spatial resolution and chemical image quality could be further improved by using probes of smaller cross section size and by incorporating a means to maintain a fixed optimal probe-to-surface distance real time, continuously adapting to the changing topography of the surface during a lane scan.

  11. Identification of Microalgae by Laser Desorption/Ionization Mass Spectrometry Coupled with Multiple Nanomatrices.

    PubMed

    Peng, Lung-Hsiang; Unnikrishnan, Binesh; Shih, Chi-Yu; Hsiung, Tung-Ming; Chang, Jeng; Hsu, Pang-Hung; Chiu, Tai-Chia; Huang, Chih-Ching

    2016-04-01

    In this study, we demonstrate a simple method to identify microalgae by surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using three different substrates: HgSe, HgTe, and HgTeSe nanostructures. The fragmentation/ionization processes of complex molecules in algae varied according to the heat absorption and transfer efficiency of the nanostructured matrices (NMs). Therefore, the mass spectra obtained for microalgae showed different patterns of m/z values for different NMs. The spectra contained both significant and nonsignificant peaks. Constructing a Venn diagram with the significant peaks obtained for algae when using HgSe, HgTe, and HgTeSe NMs in m/z ratio range 100-1000, a unique relationship among the three sets of values was obtained. This unique relationship of sets is different for each species of microalgae. Therefore, by observing the particular relationship of sets, we successfully identified different algae such as Isochrysis galbana, Emiliania huxleyi, Thalassiosira weissflogii, Nannochloris sp., Skeletonema cf. costatum, and Tetraselmis chui. This simple and cost-effective SALDI-MS analysis method coupled with multi-nanomaterials as substrates may be extended to identify other microalgae and microorganisms in real samples. Graphical Abstract Identification of microalgae by surface-assisted laser desorption/ionization mass spectrometry coupled with three different mercury-based nanosubstrates. PMID:26842733

  12. Microfabricated glow discharge plasma (MFGDP) for ambient desorption/ionization mass spectrometry.

    PubMed

    Ding, Xuelu; Zhan, Xuefang; Yuan, Xin; Zhao, Zhongjun; Duan, Yixiang

    2013-10-01

    A novel ambient ionization technique for mass spectrometry, microfabricated glow discharge plasma (MFGDP), is reported. This device is made of a millimeter-sized ceramic cavity with two platinum electrodes positioned face-to-face. He or Ar plasma can be generated by a direct current voltage of several hundreds of volts requiring a total power below 4 W. The thermal plume temperature of the He plasma was measured and found to be between 25 and 80 °C at a normal discharge current. Gaseous, liquid, creamy, and solid samples with molecular weights up to 1.5 kDa could be examined in both positive and negative mode, giving limits of detection (LOD) at or below the fg/mm(2) level. The relative standard deviation (RSD) of manual sampling ranged from 10% to ~20%, while correlation coefficients of the working curve (R(2)) are all above 0.98 with the addition of internal standards. The ionization mechanisms are examed via both optical and mass spectrometry. Due to the low temperature characteristics of the microplasma, nonthermal momentum desorption is considered to dominate the desorption process. PMID:24000803

  13. Ambient Femtosecond Laser Vaporization and Nanosecond Laser Desorption Electrospray Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Flanigan, Paul; Levis, Robert

    2014-06-01

    Recent investigations of ambient laser-based transfer of molecules into the gas phase for subsequent mass spectral analysis have undergone a renaissance resulting from the separation of vaporization and ionization events. Here, we seek to provide a snapshot of recent femtosecond (fs) duration laser vaporization and nanosecond (ns) duration laser desorption electrospray ionization mass spectrometry experiments. The former employs pulse durations of <100 fs to enable matrix-free laser vaporization with little or no fragmentation. When coupled to electrospray ionization, femtosecond laser vaporization provides a universal, rapid mass spectral analysis method requiring no sample workup. Remarkably, laser pulses with intensities exceeding 1013 W cm-2 desorb intact macromolecules, such as proteins, and even preserve the condensed phase of folded or unfolded protein structures according to the mass spectral charge state distribution, as demonstrated for cytochrome c and lysozyme. Because of the ability to vaporize and ionize multiple components from complex mixtures for subsequent analysis, near perfect classification of explosive formulations, plant tissue phenotypes, and even the identity of the manufacturer of smokeless powders can be determined by multivariate statistics. We also review the more mature field of nanosecond laser desorption for ambient mass spectrometry, covering the wide range of systems analyzed, the need for resonant absorption, and the spatial imaging of complex systems like tissue samples.

  14. Cobalt coated substrate for matrix-free analysis of small molecules by laser desorption/ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Yalcin, Talat; Li, Liang

    2009-12-01

    Small molecule analysis is one of the most challenging issues in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. We have developed a cobalt coated substrate as a target for matrix-free analysis of small molecules in laser desorption/ionization mass spectrometry. Cobalt coating of 60-70 nm thickness has been characterized by scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, and laser induced breakdown spectroscopy. This target facilitates hundreds of samples to be spotted and analyzed without mixing any matrices, in a very short time. This can save a lot of time and money and can be a very practical approach for the analysis of small molecules by laser desorption/ionization mass spectrometry.

  15. Characterization of carbon surface chemistry by combined temperature programmed desorption with in situ X-ray photoelectron spectrometry and temperature programmed desorption with mass spectrometry analysis.

    PubMed

    Brender, Patrice; Gadiou, Roger; Rietsch, Jean-Christophe; Fioux, Philippe; Dentzer, Joseph; Ponche, Arnaud; Vix-Guterl, Cathie

    2012-03-01

    The analysis of the surface chemistry of carbon materials is of prime importance in numerous applications, but it is still a challenge to identify and quantify the surface functional groups which are present on a given carbon. Temperature programmed desorption with mass spectrometry analysis (TPD-MS) and X-ray photoelectron spectroscopy with an in situ heating device (TPD-XPS) were combined in order to improve the characterization of carbon surface chemistry. TPD-MS analysis allowed the quantitative analysis of the released gases as a function of temperature, while the use of a TPD device inside the XPS setup enabled the determination of the functional groups that remain on the surface at the same temperatures. TPD-MS results were then used to add constraints on the deconvolution of the O1s envelope of the XPS spectra. Furthermore, a better knowledge of the evolution of oxygen functional groups with temperature during a thermal treatment could be obtained. Hence, we show here that the combination of these two methods allows to increase the reliability of the analysis of the surface chemistry of carbon materials. PMID:22242697

  16. Multivariate analysis of progressive thermal desorption coupled gas chromatography-mass spectrometry.

    SciTech Connect

    Van Benthem, Mark Hilary; Mowry, Curtis Dale; Kotula, Paul Gabriel; Borek, Theodore Thaddeus, III

    2010-09-01

    Thermal decomposition of poly dimethyl siloxane compounds, Sylgard{reg_sign} 184 and 186, were examined using thermal desorption coupled gas chromatography-mass spectrometry (TD/GC-MS) and multivariate analysis. This work describes a method of producing multiway data using a stepped thermal desorption. The technique involves sequentially heating a sample of the material of interest with subsequent analysis in a commercial GC/MS system. The decomposition chromatograms were analyzed using multivariate analysis tools including principal component analysis (PCA), factor rotation employing the varimax criterion, and multivariate curve resolution. The results of the analysis show seven components related to offgassing of various fractions of siloxanes that vary as a function of temperature. Thermal desorption coupled with gas chromatography-mass spectrometry (TD/GC-MS) is a powerful analytical technique for analyzing chemical mixtures. It has great potential in numerous analytic areas including materials analysis, sports medicine, in the detection of designer drugs; and biological research for metabolomics. Data analysis is complicated, far from automated and can result in high false positive or false negative rates. We have demonstrated a step-wise TD/GC-MS technique that removes more volatile compounds from a sample before extracting the less volatile compounds. This creates an additional dimension of separation before the GC column, while simultaneously generating three-way data. Sandia's proven multivariate analysis methods, when applied to these data, have several advantages over current commercial options. It also has demonstrated potential for success in finding and enabling identification of trace compounds. Several challenges remain, however, including understanding the sources of noise in the data, outlier detection, improving the data pretreatment and analysis methods, developing a software tool for ease of use by the chemist, and demonstrating our belief that

  17. Internal energy deposition with silicon nanoparticle-assisted laser desorption/ionization (SPALDI) mass spectrometry

    NASA Astrophysics Data System (ADS)

    Dagan, Shai; Hua, Yimin; Boday, Dylan J.; Somogyi, Arpad; Wysocki, Ronald J.; Wysocki, Vicki H.

    2009-06-01

    The use of silicon nanoparticles for laser desorption/ionization (LDI) is a new appealing matrix-less approach for the selective and sensitive mass spectrometry of small molecules in MALDI instruments. Chemically modified silicon nanoparticles (30 nm) were previously found to require very low laser fluence in order to induce efficient LDI, which raised the question of internal energy deposition processes in that system. Here we report a comparative study of internal energy deposition from silicon nanoparticles to previously explored benzylpyridinium (BP) model compounds during LDI experiments. The internal energy deposition in silicon nanoparticle-assisted laser desorption/ionization (SPALDI) with different fluorinated linear chain modifiers (decyl, hexyl and propyl) was compared to LDI from untreated silicon nanoparticles and from the organic matrix, [alpha]-cyano-4-hydroxycinnamic acid (CHCA). The energy deposition to internal vibrational modes was evaluated by molecular ion survival curves and indicated that the ions produced by SPALDI have an internal energy threshold of 2.8-3.7 eV. This is slightly lower than the internal energy induced using the organic CHCA matrix, with similar molecular survival curves as previously reported for LDI off silicon nanowires. However, the internal energy associated with desorption/ionization from the silicon nanoparticles is significantly lower than that reported for desorption/ionization on silicon (DIOS). The measured survival yields in SPALDI gradually decrease with increasing laser fluence, contrary to reported results for silicon nanowires. The effect of modification of the silicon particle surface with semifluorinated linear chain silanes, including fluorinated decyl (C10), fluorinated hexyl (C6) and fluorinated propyl (C3) was explored too. The internal energy deposited increased with a decrease in the length of the modifier alkyl chain. Unmodified silicon particles exhibited the highest analyte internal energy

  18. Analytical laser induced liquid beam desorption mass spectrometry of protonated amino acids and their non-covalently bound aggregates

    NASA Astrophysics Data System (ADS)

    Charvat, A.; Lugovoj, E.; Faubel, M.; Abel, B.

    2002-09-01

    We have used analytical laser induced liquid beam desorption in combination with high resolution mass spectrometry (m/Δ mgeq 1 000) for the study of protonated amino acids (ornithine, citrulline, lysine, arginine) and their non-covalently bound complexes in the gas phase desorbed from water solutions. We report studies in which the desorption mechanism has been investigated. The results imply that biomolecule desorption at our conditions is a single step process involving laser heating of the solvent above its supercritical temperature, a rapid expansion, ion recombination and finally isolation and desorption of only a small fraction of preformed ions and charged aggregates. In addition, we report an investigation of the aqueous solution concentration and pH-dependence of the laser induced desorption of protonated species (monomers and dimers). The experimental findings suggest that the desorption process depends critically upon the proton affinity of the molecules, the concentration of other ions, and of the pH value of the solution. Therefore the ion concentrations measured in the gas phase very likely reflect solution properties (equilibrium concentrations). Arginine self-assembles large non-covalent singly protonated multimers (n=1...8) when sampled by IR laser induced water beam desorption mass spectrometry. The structures of these aggregates may resemble those of the solid state and may be preformed in solution prior to desorption. A desorption of mixtures of amino acids in water solution enabled us to study (mixed) protonated dimers, one of the various applications of the present technique. Reasons for preferred dimerization leading to simple cases of molecular recognition as well as less preferred binding is discussed in terms of the number of specific H-bonds that can be established in the clusters.

  19. High-Resolution Desorption Electrospray Ionization Mass Spectrometry for Chemical Characterization of Organic Aerosols

    SciTech Connect

    Laskin, Julia; Laskin, Alexander; Roach, Patrick J.; Slysz, Gordon W.; Anderson, Gordon A.; Nizkorodov, Serguei; Bones, David L.; Nguyen, Lucas

    2010-03-01

    Characterization of the chemical composition and chemical transformations of secondary organic aerosol (SOA) is both a major challenge and the area of greatest uncertainty in current aerosol research. This study presents the first application of desorption electrospray ionization combined with high-resolution mass spectrometry (DESI-MS) for detailed chemical characterization and studies of chemical aging of OA collected on Teflon substrates. DESI-MS offers unique advantages both for detailed characterization of chemically labile components in OA that cannot be detected using more traditional electrospray ionization mass spectrometry (ESI-MS) and for studying chemical aging of OA. DESI-MS enables rapid characterization of OA samples collected on substrates by eliminating the sample preparation stage. In addition, it enables detection and structural characterization of chemically labile molecules in OA samples by minimizing the residence time of analyte in the solvent. SOA produced by the ozonolysis of limonene (LSOA) was allowed to react with gaseous ammonia. Chemical aging resulted in measurable changes in the optical properties of LSOA observed using UV- visible spectroscopy. DESI-MS combined with tandem mass spectrometry experiments (MS/MS) enabled identification of species in aged LSOA responsible for absorption of the visible light. Detailed analysis of the experimental data allowed us to identify chemical changes induced by reactions of LSOA constituents with ammonia and distinguish between different mechanisms of chemical aging.

  20. Direct analysis of samples by mass spectrometry: From elements to bio-molecules using laser ablation inductively couple plasma mass spectrometry and laser desorption/ionization mass spectrometry

    SciTech Connect

    Perdian, David C.

    2009-01-01

    Mass spectrometric methods that are able to analyze solid samples or biological materials with little or no sample preparation are invaluable to science as well as society. Fundamental research that has discovered experimental and instrumental parameters that inhibit fractionation effects that occur during the quantification of elemental species in solid samples by laser ablation inductively coupled plasma mass spectrometry is described. Research that determines the effectiveness of novel laser desorption/ionization mass spectrometric methods for the molecular analysis of biological tissues at atmospheric pressure and at high spatial resolution is also described. A spatial resolution is achieved that is able to analyze samples at the single cell level.

  1. Thin-Layer Chromatography/Desorption Electrospray Ionization Mass Spectrometry: Investigation of Goldenseal Alkaloids

    SciTech Connect

    Van Berkel, Gary J; Tomkins, Bruce A; Kertesz, Vilmos

    2007-01-01

    Desorption electrospray ionization mass spectrometry was investigated as a means to qualitatively identify and to quantify analytes directly from developed normal-phase thin layer chromatography plates. The atmospheric sampling capillary of a commercial ion trap mass spectrometer was extended to permit sampling and ionization of analytes in bands separated on intact TLC plates (up to 10 cm x 10 cm). A surface positioning software package and the appropriate hardware enabled computer-controlled surface scanning along the length of development lanes or at fixed RF value across the plates versus the stationary desorption electrospray emitter. Goldenseal (Hydrastis canadensis) and related alkaloids and commercial dietary supplements were used as standards and samples. Alkaloid standards and samples were spotted and separated on aluminum- or glass-backed plates using established literature methods. The mass spectral signal levels as a function of desorption spray solvent were investigated with acetonitrile proving superior to methanol. The detection levels (ca. 5 ng each or 14 -28 pmol) in mass spectral full scan mode were determined statistically from the calibration curves (2.5 - 100 pmol) for the standards berberine, palmatine and hydrastinine spotted as a mixture and separated on the plates. Qualitative screening of the major alkaloids present in six different over-the-counter "goldenseal" dietary supplements was accomplished by obtaining full scan mass spectra during surface scans along the development lane in the direction of increasing RF value. In one sample, alkaloids were detected that strongly suggested the presence of at least one additional herb undeclared on the product label. These same data indicated the misidentification of one of the alkaloids in the TLC literature. Quantities of the alkaloids present in two of the samples determined using the mass spectral data were in reasonable agreement with the label values indicating the quantitative ability of

  2. Development and Applications of Liquid Sample Desorption Electrospray Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Zheng, Qiuling; Chen, Hao

    2016-06-01

    Desorption electrospray ionization mass spectrometry (DESI-MS) is a recent advance in the field of analytical chemistry. This review surveys the development of liquid sample DESI-MS (LS-DESI-MS), a variant form of DESI-MS that focuses on fast analysis of liquid samples, and its novel analy-tical applications in bioanalysis, proteomics, and reaction kinetics. Due to the capability of directly ionizing liquid samples, liquid sample DESI (LS-DESI) has been successfully used to couple MS with various analytical techniques, such as microfluidics, microextraction, electrochemistry, and chromatography. This review also covers these hyphenated techniques. In addition, several closely related ionization methods, including transmission mode DESI, thermally assisted DESI, and continuous flow–extractive DESI, are briefly discussed. The capabilities of LS-DESI extend and/or complement the utilities of traditional DESI and electrospray ionization and will find extensive and valuable analytical application in the future.

  3. Direct Surface Analysis of Fungal Species by Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

    SciTech Connect

    Valentine, Nancy B. ); Wahl, Jon H. ); Kingsley, Mark T. ); Wahl, Karen L. )

    2001-12-01

    Intact spores and/or hyphae of Aspergillus niger, Rhizopus oryzae, Trichoderma reesei and Phanerochaete chrysosporium are analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). This study investigates various methods of sample preparation and matrices to determine optimum collection and analysis criteria for fungal analysis by MALDI-MS. Fungi are applied to the MALDI sample target as untreated, sonicated, acid/heat treated, or blotted directly from the fungal culture with double-stick tape. Ferulic acid or sinapinic acid matrix solution is layered over the dried samples and analyzed by MALDI-MS. Statistical analysis of the data show that simply using double stick tape to collect and transfer to a MALDI sample plate typically worked as well as the other preparation methods, but requires the least sample handling.

  4. Shotgun Approach for Quantitative Imaging of Phospholipids Using Nanospray Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Lanekoff, Ingela T.; Thomas, Mathew; Laskin, Julia

    2014-02-04

    Mass spectrometry imaging (MSI) has been extensively used for determining spatial distributions of molecules in biological samples, and there is increasing interest in using MSI for quantification. Nanospray desorption electrospray ionization, or nano-DESI, is an ambient MSI technique where a solvent is used for localized extraction of molecules followed by nanoelectrospray ionization. Doping the nano-DESI solvent with carefully selected standards enables online quantification during MSI experiments. In this proof-of-principle study, we demonstrate this quantification approach can be extended to provide shotgun-like quantification of phospholipids in thin brain tissue sections. Specifically, two phosphatidylcholine (PC) standards were added to the nano-DESI solvent for simultaneous imaging and quantification of 22 PC species observed in nano-DESI MSI. Furthermore, by combining the quantitative data obtained in the individual pixels, we demonstrate quantification of these PC species in seven different regions of a rat brain tissue section.

  5. Ammonium Ion Exchanged Zeolite for Laser Desorption/Ionization Mass Spectrometry of Phosphorylated Peptides

    PubMed Central

    Yang, Mengrui; Fujino, Tatsuya

    2015-01-01

    α-Cyano-4-hydroxycinnamic acid (CHCA), an organic matrix molecule for matrix-assisted laser desorption/ionization mass spectrometry, was adsorbed to NH4+-type zeolite surface, and this new matrix was used for the detection of low-molecular-weight compounds. It was found that this matrix could simplify the mass spectrum in the low-molecular-weight region and prevent interference from fragments and alkali metal ion adducted species. CHCA adsorbed to NH4+-type ZSM5 zeolite (CHCA/NH4ZSM5) was used to measure atropine and aconitine, two toxic alkaloids in plants. In addition, CHCA/NH4ZSM5 enabled us to detect phosphorylated peptides; peaks of the protonated peptides had higher intensities than the peaks observed using CHCA only. PMID:26448749

  6. Imaging of Lipids and Metabolites Using Nanospray Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Lanekoff, Ingela; Laskin, Julia

    2015-01-17

    In recent years, mass spectroscopy imaging (MSI) has emerged as a foundational technique in metabolomics and drug screening providing deeper understanding of complex mechanistic pathways within biochemical systems and biological organisms. We have been invited to contribute a chapter to a new Springer series volume, entitled “Mass Spectrometry Imaging of Small Molecules”. The volume is planned for the highly successful lab protocol series Methods in Molecular Biology, published by Humana Press, USA. The volume is aimed to equip readers with step-by-step mass spectrometric imaging protocols and bring rapidly maturing methods of MS imaging to life science researchers. The chapter will provide a detailed protocol of ambient MSI by use of nanospray desorption electrospray ionization.

  7. Matrix-Assisted Laser Desorption Ionization Imaging Mass Spectrometry: In Situ Molecular Mapping

    PubMed Central

    Angel, Peggi M.; Caprioli, Richard M.

    2013-01-01

    Matrix-assisted laser desorption ionization imaging mass spectrometry (IMS) is a relatively new imaging modality that allows mapping of a wide range of biomolecules within a thin tissue section. The technology uses a laser beam to directly desorb and ionize molecules from discrete locations on the tissue that are subsequently recorded in a mass spectrometer. IMS is distinguished by the ability to directly measure molecules in situ ranging from small metabolites to proteins, reporting hundreds to thousands of expression patterns from a single imaging experiment. This article reviews recent advances in IMS technology, applications, and experimental strategies that allow it to significantly aid in the discovery and understanding of molecular processes in biological and clinical samples. PMID:23259809

  8. Matrix assisted laser desorption ionization-time of flight mass spectrometry analysis of hyaluronan oligosaccharides

    PubMed Central

    Sakai, Shinobu; Hirano, Kana; Toyoda, Hidenao; Linhardt, Robert J.; Toida, Toshihiko

    2014-01-01

    A new method is presented for the identification of oligosaccharides obtained by enzymatic digestion of hyaluronan (HA) with bacterial hyaluronidase (E.C. 4.2.2.1, from Streptomyces hyalurolyticus) using matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOFMS). Mixtures containing HA oligosaccharides of tetrasaccharide (4-mer)–34-mer were analyzed using this method. The carboxyl groups of the glucuronate residues in the prepared HA oligomers, were modified as the acidic form (—COOH), sodium salts (—COONa), organic ammonium salts, or methylesters before MALDI-TOFMS measurement. Among these samples, the methylester form of glucuronate residues in HA oligosaccharides, prepared by methylation using trimethylsilyl diazomethane, afforded high sensitivity for spectra. This simple modification method for carboxyl group methylation of acidic polysaccharides [Hirano et al., Carbohydr. Res., 340, (2005) 2297–2304] provides samples suitable for MALDI-TOF mass spectrometric analysis throughout a significantly enhanced range of masses. PMID:17543609

  9. Molecular Characterization of Organic Aerosols Using Nanospray Desorption/Electrospray Ionization-Mass Spectrometry

    SciTech Connect

    Roach, Patrick J.; Laskin, Julia; Laskin, Alexander

    2010-10-01

    Nanospray desorption electrospray ionization (Nano-DESI) combined with high-resolution mass spectrometry (HR/MS) is a promising approach for detailed chemical characterization of atmospheric organic aerosol (OA) collected in laboratory and field experiments. In Nano-DESI analyte is desorbed into a solvent bridge formed between two capillaries and the analysis surface, which enables fast and efficient characterization of OA collected on substrates without special sample preparation. Stable signals achieved using Nano-DESI make it possible to obtain high-quality HR/MS data using only a small amount of material (<10 ng). Furthermore, Nano-DESI enables efficient detection of chemically labile compounds in OA, which is important for understanding chemical aging phenomena.

  10. Development and Applications of Liquid Sample Desorption Electrospray Ionization Mass Spectrometry.

    PubMed

    Zheng, Qiuling; Chen, Hao

    2016-06-12

    Desorption electrospray ionization mass spectrometry (DESI-MS) is a recent advance in the field of analytical chemistry. This review surveys the development of liquid sample DESI-MS (LS-DESI-MS), a variant form of DESI-MS that focuses on fast analysis of liquid samples, and its novel analy-tical applications in bioanalysis, proteomics, and reaction kinetics. Due to the capability of directly ionizing liquid samples, liquid sample DESI (LS-DESI) has been successfully used to couple MS with various analytical techniques, such as microfluidics, microextraction, electrochemistry, and chromatography. This review also covers these hyphenated techniques. In addition, several closely related ionization methods, including transmission mode DESI, thermally assisted DESI, and continuous flow-extractive DESI, are briefly discussed. The capabilities of LS-DESI extend and/or complement the utilities of traditional DESI and electrospray ionization and will find extensive and valuable analytical application in the future. PMID:27145689

  11. Application of 252Cf plasma desorption mass spectrometry in dental research

    NASA Astrophysics Data System (ADS)

    Fritsch, Hans-Walter; Schmidt, Lothar; Köhl, Peter; Jungclas, Hartmut; Duschner, Heins

    1993-07-01

    Topically applied fluorides introduced in dental hygiene products elevate the concentration levels of fluoride in oral fluids and thus also affect chemical reactions of enamel de- and remineralisation. The chemical reactions on the surface of tooth enamel still are a subject of controversy. Here 252Cf-plasma desorption mass spectrometry and argon ion etching are used to analyse the molecular structure of the upper layes of enamel. The mass spectrum of untreated enamel is characterised by a series of cluster ions containing phosphate. It is evident that under certain conditions the molecular structure of the surface enamel is completely transformed by treatment with fluorides. The result of the degradation and precipitation processes is reflected by a total replacement of the phosphate by fluoride in the measured cluster ion distribution. Stepwise etching of the upper layers by Ar+ ions reveals the transition from a nearly pure CaF2 structure to the unchanged composition of the enamel mineral.

  12. Miniaturizing sample spots for matrix-assisted laser desorption/ionization mass spectrometry

    PubMed Central

    Tu, Tingting; Gross, Michael L.

    2009-01-01

    The trend of miniaturization in bioanalytical chemistry is shifting from technical development to practical application. In matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), progress in miniaturizing sample spots has been driven by the needs to increase sensitivity and speed, to interface with other analytical microtechnologies, and to develop miniaturized instrumentation. We review recent developments in miniaturizing sample spots for MALDI-MS. We cover both target modification and microdispensing technologies, and we emphasize the benefits with respect to sensitivity, throughput and automation. We hope that this review will encourage further method development and application of miniaturized sample spots for MALDI-MS, so as to expand applications in analytical chemistry, protein science and molecular biology. PMID:20161086

  13. Desorption ElectroSpray Ionization - Orbitrap Mass Spectrometry of synthetic polymers and copolymers.

    PubMed

    Friia, Manel; Legros, Véronique; Tortajada, Jeanine; Buchmann, William

    2012-08-01

    Desorption ElectroSpray Ionization (DESI) - Orbitrap Mass Spectrometry (MS) was evaluated as a new tool for the characterization of various industrial synthetic polymers (poly(ethylene glycol), poly(propylene glycol), poly(methylmethacrylate), poly(dimethylsiloxane)) and copolymers, with masses ranging from 500 g.mol(-1) up to more than 20 000 g.mol(-1) . Satisfying results in terms of signal stability and sensitivity were obtained from hydrophobic surfaces (HTC Prosolia) with a mixture water/methanol (10/90) as spray solvent in the presence of sodium salt. Taking into account the formation of multiplied charged species by DESI-MS, a strategy based on the use of a deconvolution software followed by the automatic assignment of the ions was described allowing the rapid determination of M(n) , M(w) and PDI values. DESI-Orbitrap MS results were compared to those obtained from matrix-assisted laser desorption/ionization- time-of-flight MS and gel permeation chromatography. An application of DESI-Orbitrap MS for the detection and identification of polymers directly from cosmetics was described. PMID:22899511

  14. Imaging of Proteins in Tissue Samples Using Nanospray Desorption Electrospray Ionization Mass Spectrometry.

    PubMed

    Hsu, Cheng-Chih; Chou, Pi-Tai; Zare, Richard N

    2015-11-17

    Chemical maps of tissue samples provide important information on biological processes therein. Recently, advances in tissue imaging have been achieved using ambient ionization techniques, such as desorption electrospray ionization mass spectrometry (DESI-MS), but such techniques have been almost exclusively confined to the mapping of lipids and metabolites. We report here the use of nanospray desorption electrospray ionization (nanoDESI) that allows us to image proteins in tissue samples in a label-free manner at atmospheric pressure with only minimum sample preparation. Multiply charged proteins with masses up to 15 kDa were successfully detected by nanoDESI using an LTQ Orbitrap mass spectrometer. In an adult mice brain section, expression of proteins including ubiquitin, β-thymosin, myelin basic protein, and hemoglobin were spatially mapped and characterized. We also determined the location of methylation on myelin basic protein. This imaging modality was further implemented to MYC-induced lymphomas. We observed an array of truncated proteins in the region where normal thymus cells were infiltrated by tumor cells, in contrast to healthy tissue. PMID:26509582

  15. High-resolution atmospheric pressure infrared laser desorption/ionization mass spectrometry imaging of biological tissue.

    PubMed

    Römpp, Andreas; Schäfer, Karl Christian; Guenther, Sabine; Wang, Zheng; Köstler, Martin; Leisner, Arne; Paschke, Carmen; Schramm, Thorsten; Spengler, Bernhard

    2013-09-01

    An atmospheric pressure laser desorption/ionization mass spectrometry imaging ion source has been developed that combines high spatial resolution and high mass resolution for the in situ analysis of biological tissue. The system is based on an infrared laser system working at 2.94 to 3.10 μm wavelength, employing a Nd:YAG laser-pumped optical parametrical oscillator. A Raman-shifted Nd:YAG laser system was also tested as an alternative irradiation source. A dedicated optical setup was used to focus the laser beam, coaxially with the ion optical axis and normal to the sample surface, to a spot size of 30 μm in diameter. No additional matrix was needed for laser desorption/ionization. A cooling stage was developed to reduce evaporation of physiological cell water. Ions were formed under atmospheric pressure and transferred by an extended heated capillary into the atmospheric pressure inlet of an orbital trapping mass spectrometer. Various phospholipid compounds were detected, identified, and imaged at a pixel resolution of up to 25 μm from mouse brain tissue sections. Mass accuracies of better than 2 ppm and a mass resolution of 30,000 at m/z = 400 were achieved for these measurements. PMID:23877173

  16. Molecular Ionization-Desorption Analysis Source (MIDAS) for Mass Spectrometry: Thin-Layer Chromatography.

    PubMed

    Winter, Gregory T; Wilhide, Joshua A; LaCourse, William R

    2016-02-01

    Molecular ionization-desorption analysis source (MIDAS), which is a desorption atmospheric pressure chemical ionization (DAPCI) type source, for mass spectrometry has been developed as a multi-functional platform for the direct sampling of surfaces. In this article, its utility for the analysis of thin-layer chromatography (TLC) plates is highlighted. Amino acids, which are difficult to visualize without staining reagents or charring, were detected and identified directly from a TLC plate. To demonstrate the full potential of MIDAS, all active ingredients from an analgesic tablet, separated on a TLC plate, were successfully detected using both positive and negative ion modes. The identity of each of the compounds was confirmed from their mass spectra and compared against standards. Post separation, the chemical signal (blue permanent marker) as reference marks placed at the origin and solvent front were used to calculate retention factor (Rf) values from the resulting ion chromatogram. The quantitative capabilities of the device were exhibited by scanning caffeine spots on a TLC plate of increasing sample amount. A linear curve based on peak are, R2 = 0.994, was generated for seven spots ranging from 50 to 1000 ng of caffeine per spot. PMID:26471042

  17. Laser Desorption Postionization Mass Spectrometry of Antibiotic-Treated Bacterial Biofilms using Tunable Vacuum Ultraviolet Radiation

    PubMed Central

    Gasper, Gerald L.; Takahashi, Lynelle K.; Zhou, Jia; Ahmed, Musahid; Moore, Jerry F.; Hanley, Luke

    2010-01-01

    Laser desorption postionization mass spectrometry (LDPI-MS) with 8.0 – 12.5 eV vacuum ultraviolet synchrotron radiation is used to single photon ionize antibiotics and extracellular neutrals that are laser desorbed both neat and from intact bacterial biofilms. Neat antibiotics are optimally detected using 10.5 eV LDPI-MS, but can be ionized using 8.0 eV radiation, in agreement with prior work using 7.87 eV LDPI-MS. Tunable vacuum ultraviolet radiation also postionizes laser desorbed neutrals of antibiotics and extracellular material from within intact bacterial biofilms. Different extracellular material is observed by LDPI-MS in response to rifampicin or trimethoprim antibiotic treatment. Once again, 10.5 eV LDPI-MS displays the optimum trade-off between improved sensitivity and minimum fragmentation. Higher energy photons at 12.5 eV produce significant parent ion signal, but fragment intensity and other low mass ions are also enhanced. No matrix is added to enhance desorption, which is performed at peak power densities insufficient to directly produce ions, thus allowing observation of true VUV postionization mass spectra of antibiotic treated biofilms. PMID:20712373

  18. Direct protein detection from biological media through electrospray-assisted laser desorption ionization/mass spectrometry.

    PubMed

    Huang, Min-Zong; Hsu, Hsiu-Jung; Lee, Jen-Yih; Jeng, Jingyueh; Shiea, Jentaie

    2006-05-01

    We report here using a novel technology-electrospray-assisted laser desorption ionization (ELDI)/mass spectrometry-for the rapid and sensitive detection of the major proteins that exist in dried biological fluids (e.g., blood, tears, saliva, serum), bacterial cultures, and tissues (e.g., porcine liver and heart) under ambient conditions. This technique required essentially no sample pretreatment. The proteins in the samples were desorbed using a pulsed nitrogen laser without the assistance of an organic matrix. The desorbed protein molecules were then post-ionized through their fusion into the charged solvent droplets produced from the electrospray of an acidic methanol solution; electrospray ionization (ESI) proceeded from the newly formed droplets to generate the ESI-like protein ions. This new ionization approach combines some of the features of electrospray ionization with those of matrix-assisted laser desorption ionization (MALDI), that is, sampling of a solid surface with spatial resolution, generating ESI-like mass spectra of the desorbed proteins, and operating under ambient conditions. PMID:16674100

  19. Laser Desorption Postionization Mass Spectrometry of Antibiotic-Treated Bacterial Biofilms using Tunable Vacuum Ultraviolet Radiation

    SciTech Connect

    Gasper, Gerald L; Takahashi, Lynelle K; Zhou, Jia; Ahmed, Musahid; Moore, Jerry F; Hanley, Luke

    2010-08-04

    Laser desorption postionization mass spectrometry (LDPI-MS) with 8.0 ? 12.5 eV vacuum ultraviolet synchrotron radiation is used to single photon ionize antibiotics andextracellular neutrals that are laser desorbed both neat and from intact bacterial biofilms. Neat antibiotics are optimally detected using 10.5 eV LDPI-MS, but can be ionized using 8.0 eV radiation, in agreement with prior work using 7.87 eV LDPI-MS. Tunable vacuum ultraviolet radiation also postionizes laser desorbed neutrals of antibiotics and extracellular material from within intact bacterial biofilms. Different extracellular material is observed by LDPI-MS in response to rifampicin or trimethoprim antibiotic treatment. Once again, 10.5 eV LDPI-MS displays the optimum trade-off between improved sensitivity and minimum fragmentation. Higher energy photons at 12.5 eV produce significant parent ion signal, but fragment intensity and other low mass ions are also enhanced. No matrix is added to enhance desorption, which is performed at peak power densities insufficient to directly produce ions, thus allowing observation of true VUV postionization mass spectra of antibiotic treated biofilms.

  20. Laser desorption mass spectrometry and small angle neutron scattering of heavy fossil materials

    SciTech Connect

    Hunt, J.E.; Winans, R.E.; Thiyagarajan, P.

    1997-09-01

    The determination of the structural building blocks and the molecular weight range of heavy hydrocarbon materials is of crucial importance in research on their reactivity and for their processing. The chemically and physically heterogenous nature of heavy hydrocarbon materials, such as coals, heavy petroleum fractions, and residues, dictates that their structure and reactivity patterns be complicated. The problem is further complicated by the fact that the molecular structure and molecular weight distribution of these materials is not dependent on a single molecule, but on a complex mixture of molecules which vary among coals and heavy petroleum samples. Laser Desorption mass spectrometry (LDMS) is emerging as a technique for molecular weight determination having found widespread use in biological polymer research, but is still a relatively new technique in the fossil fuel area. Small angle neutron scattering (SANS) provides information on the size and shape of heavy fossil materials. SANS offers the advantages of high penetration power even in thick cells at high temperatures and high contrast for hydrocarbon systems dispersed in deuterated solvents. LDMS coupled with time of flight has the advantages of high sensitivity and transmission and high mass range. We have used LDMS to examine various heavy fossil-derived materials including: long chain hydrocarbons, asphaltenes from petroleum vacuum resids, and coals. This paper describes the application of laser desorption and small angle neutron scattering techniques to the analysis of components in coals, petroleum resids and unsaturated polymers.

  1. Molecular Ionization-Desorption Analysis Source (MIDAS) for Mass Spectrometry: Thin-Layer Chromatography

    NASA Astrophysics Data System (ADS)

    Winter, Gregory T.; Wilhide, Joshua A.; LaCourse, William R.

    2016-02-01

    Molecular ionization-desorption analysis source (MIDAS), which is a desorption atmospheric pressure chemical ionization (DAPCI) type source, for mass spectrometry has been developed as a multi-functional platform for the direct sampling of surfaces. In this article, its utility for the analysis of thin-layer chromatography (TLC) plates is highlighted. Amino acids, which are difficult to visualize without staining reagents or charring, were detected and identified directly from a TLC plate. To demonstrate the full potential of MIDAS, all active ingredients from an analgesic tablet, separated on a TLC plate, were successfully detected using both positive and negative ion modes. The identity of each of the compounds was confirmed from their mass spectra and compared against standards. Post separation, the chemical signal (blue permanent marker) as reference marks placed at the origin and solvent front were used to calculate retention factor (Rf) values from the resulting ion chromatogram. The quantitative capabilities of the device were exhibited by scanning caffeine spots on a TLC plate of increasing sample amount. A linear curve based on peak are, R2 = 0.994, was generated for seven spots ranging from 50 to 1000 ng of caffeine per spot.

  2. Detection of Biosignatures by Geomatrix-Assisted Laser Desorption/Ionization (GALDI) Mass Spectrometry

    SciTech Connect

    Jill R. Scott; Beizhan Yan; Daphne L. Stoner; J. Michelle Kotler; Nancy W. Hinman

    2007-04-01

    Identification of mineral-associated biosignatures is of significance for retrieving biochemical information from geological records here on Earth and detecting signs of life on other planets, such as Mars. The importance of the geomatrix for identifying amino acids (e.g., histidine, threonine, and cysteine) and small proteins (e.g., gramicidin S) was investigated by laser desorption Fourier transform mass spectrometry. The investigated geomatrices include analogues of Fe-bearing minerals such as hematite and Na-bearing evaporites (e.g., halite). Samples were prepared by two methods: 1) application of analyte to the geomatrix surface and 2) production of homogenous analyte:geomatrix mixtures. Comparison of the two sample preparation methods revealed that the mixing method produces a better signal/noise ratio than surface application for the analyses of amino acids. The composition of the geomatrix has a profound influence on the detection of biomolecules. Peaks corresponding to the cation-attached biomolecular ions were observed for the Na-bearing evaporite analogue. No detectable peaks for the biomolecular ion species were observed when the biomolecules were associated with Fe-bearing minerals. Instead, only minor peaks were observed that may correspond to ions from fragments of the biomolecules. Depending on the underlying mineral composition, geomatrix-assisted laser desorption/ionization shows promise for directly identifying biosignatures associated with minerals.

  3. Desorption electrospray ionization mass spectrometry: direct toxicological screening and analysis of illicit Ecstasy tablets.

    PubMed

    Leuthold, Luc Alexis; Mandscheff, Jean-François; Fathi, Marc; Giroud, Christian; Augsburger, Marc; Varesio, Emmanuel; Hopfgartner, Gérard

    2006-01-01

    Desorption electrospray ionization mass spectrometry (DESI-MS) was used as a simple and rapid way to analyze drug tablets and powders without sample preparation. Experiments were performed with a home-made DESI source coupled to a triple-quadrupole linear-ion trap (QqQ(LIT)) mass spectrometer. Twenty-one commercial drugs as well as some illicit Ecstasy tablets and powders were analyzed. MS spectra almost exclusively showed the protonated or deprotonated ion of the drug after directing the pneumatically assisted electrospray onto the tablet's surface. With some tablets, inhomogeneity of the surface resulted in different spectra depending on the spot analyzed, thus showing that DESI could be used for imaging. Directly triggered MS/MS spectra were used for confirmatory analysis, with analysis times often below 10 s per tablet. For illicit Ecstasy tablets, DESI-MS, GC/MS and LC/MS analyses provided similar qualitative results for the main analytes. With MS/MS spectra library comparison or exact mass measurements, this technique could become very powerful for the rapid analysis of unknown tablets and shows the great potential of desorption techniques as an alternative to solution-based analysis. PMID:16331738

  4. Characterization of ballpoint pen inks by thermal and desorption and gas chromatography-mass spectrometry.

    PubMed

    Bügler, Jürgen H; Buchner, Hans; Dallmayer, Anton

    2005-09-01

    The characterization of ink on paper is of importance for dating and comparing questioned ink entries in forensic document examination. Inks are commonly characterized by their colorant profile that is identified by well-established analytical methods. Numerous ink formulations show identical colorant profiles, though. In order to differentiate inks that are not distinguishable by colorant analysis, a method for the characterization of colorless ink ingredients, namely binders, solvents and additives is necessary. In this paper, we propose a technique for the analysis of colorless compounds in ballpoint inks using direct thermal desorption of the ink on paper followed by chemical analysis of the desorbed volatile compounds by gas chromatography-mass spectrometry. As compared to liquid extraction and subsequent analysis of the extracts, the technique avoids possible contamination risks. Sensitivity is very high due to the enrichment of volatile components by thermal desorption. Even from old samples, the chromatograms obtained by the method enable the determination of binder polymers, solvents and additives. Pure binders as used by ink manufacturers were analyzed for unambiguous assignment of analytical results to specific polymers. To prove the practical applicability, we analyzed 121 ballpoint pens, not all having the same colorant profile, and grouped the pens into resin and solvent categories. PMID:16225233

  5. Laser desorption time-of-flight mass spectrometry of vacuum UV photo-processed methanol ice

    NASA Astrophysics Data System (ADS)

    Paardekooper, D. M.; Bossa, J.-B.; Linnartz, H.

    2016-07-01

    Context. Methanol in the interstellar medium mainly forms upon sequential hydrogenation of solid CO. With typical abundances of up to 15% (with respect to water) it is an important constituent of interstellar ices where it is considered as a precursor in the formation of large and complex organic molecules (COMs), e.g. upon vacuum UV (VUV) photo-processing or exposure to cosmic rays. Aims: This study aims at detecting novel complex organic molecules formed during the VUV photo-processing of methanol ice in the laboratory using a technique more sensitive than regular surface diagnostic tools. In addition, the formation kinetics of the main photo-products of methanol are unravelled for an astronomically relevant temperature (20 K) and radiation dose. Methods: The VUV photo-processing of CH3OH ice is studied by applying laser desorption post-ionisation time-of-flight mass spectrometry (LDPI TOF-MS), and analysed by combining molecule-specific fragmentation and desorption features. Results: The mass spectra correspond to fragment ions originating from a number of previously recorded molecules and from new COMs, such as the series (CO)xH, with x = 3 and y < 3x-1, to which prebiotic glycerin belongs. The formation of these large COMs has not been reported in earlier photolysis studies and suggests that such complex species may form in the solid state under interstellar conditions.

  6. On-probe pyrolysis desorption ecectrospray ionization (DESI) mass spectrometry for the analysis of non-volatile pyrolysis products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An on-probe pyrolyzer has been constructed and interfaced with desorption electrospray ionization (DESI) mass spectrometry (MS) for the rapid analysis of non-volatile pyrolysis products. The detection and analysis of non-volatile pyrolysis products of peptides, proteins and the synthetic polymer pol...

  7. Development of matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) for plant metabolite analysis

    SciTech Connect

    Korte, Andrew R

    2014-12-01

    This thesis presents efforts to improve the methodology of matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) as a method for analysis of metabolites from plant tissue samples. The first chapter consists of a general introduction to the technique of MALDI-MSI, and the sixth and final chapter provides a brief summary and an outlook on future work.

  8. Atmospheric Pressure-Thermal Desorption (AP-TD)/Electrospray Ionization-Mass Spectrometry for the Rapid Analysis of Bacillus Spores

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A technique is described where an atmospheric pressure-thermal desorption (AP-TD) device and electrospray ionization (ESI)-mass spectrometry are coupled and used for the rapid analysis of Bacillus spores in complex matrices. The resulting AP-TD/ESI-MS technique combines the generation of volatile co...

  9. Desorption electrospray ionization mass spectrometry for trace analysis of agrochemicals in food.

    PubMed

    García-Reyes, Juan F; Jackson, Ayanna U; Molina-Díaz, Antonio; Cooks, R Graham

    2009-01-15

    Desorption electrospray ionization (DESI) is applied to the rapid, in situ, direct qualitative and quantitative (ultra)trace analysis of agrochemicals in foodstuffs. To evaluate the potential of DESI mass spectrometry (MS) in toxic residue testing in food, 16 representative multiclass agricultural chemicals (pesticides, insecticides, herbicides, and fungicides) were selected (namely, ametryn, amitraz, azoxystrobin, bitertanol, buprofezin, imazalil, imazalil metabolite, isofenphos-methyl, malathion, nitenpyram, prochloraz, spinosad, terbuthylazine, thiabendazole, and thiacloprid). The DESI-MS experiments were performed using 3 microL of solution spotted onto conventional smooth poly(tetrafluoroethylene) (PTFE) surfaces, with examination by MS and tandem mass spectrometry (MS/MS) using an ion trap mass spectrometer. Optimization of the spray solvent led to the use of acetonitrile/water (80:20) (v/v), with 1% formic acid. Most of the compounds tested showed remarkable sensitivity in the positive ion mode, approaching that attainable with conventional direct infusion electrospray mass spectrometry. To evaluate the potential of the proposed approach in real samples, different experiments were performed including the direct DESI-MS/MS analysis of fruit peels and also of fruit/vegetable extracts. The results proved that DESI allows the detection and confirmation of traces of agrochemicals in actual market-purchased samples. In addition, MS/MS confirmation of selected pesticides in spiked vegetable extracts was obtained at absolute levels as low as 1 pg for ametryn. Quantitation of imazalil residues was also undertaken using an isotopically labeled standard. The data obtained were in agreement with those from the liquid chromatography mass spectrometry (LC-MS) reference method, with relative standard deviation (RSD) values consistently below 15%. The results obtained demonstrate the sensitivity of DESI as they meet the stringent European Union pesticide regulation

  10. Study of Electrochemical Reactions Using Nanospray Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Liu, Pengyuan; Lanekoff, Ingela T.; Laskin, Julia; Dewald, Howard D.; Chen, Hao

    2012-07-03

    The combination of electrochemistry (EC) and mass spectrometry (MS) is a powerful analytical tool for studying mechanisms of redox reactions, identification of products and intermediates, and online derivatization/recognition of analytes. This work reports a new coupling interface for EC/MS by employing nanospray desorption electrospray ionization (nano-DESI), a recently developed ambient ionization method. We demonstrate online coupling of nano-DESI-MS with a traditional electrochemical flow cell, in which the electrolyzed solution emanating from the cell is ionized by nano-DESI for MS analysis. Furthermore, we show first coupling of nano-DESI-MS with an interdigitated array (IDA) electrode enabling chemical analysis of electrolyzed samples directly from electrode surfaces. Because of its inherent sensitivity, nano-DESI enables chemical analysis of small volumes and concentrations of sample solution. Specifically, good-quality signal of dopamine and its oxidized form, dopamine ortho-quinone, was obtained using 10 μL of 1 μM solution of dopamine on the IDA. Oxidation of dopamine, reduction of benzodiazepines, and electrochemical derivatization of thiol groups were used to demonstrate the performance of the technique. Our results show the potential of nano-DESI as a novel interface for electrochemical mass spectrometry research.

  11. High throughput volatile fatty acid skin metabolite profiling by thermal desorption secondary electrospray ionisation mass spectrometry.

    PubMed

    Martin, Helen J; Reynolds, James C; Riazanskaia, Svetlana; Thomas, C L Paul

    2014-09-01

    The non-invasive nature of volatile organic compound (VOC) sampling from skin makes this a priority in the development of new screening and diagnostic assays. Evaluation of recent literature highlights the tension between the analytical utility of ambient ionisation approaches for skin profiling and the practicality of undertaking larger campaigns (higher statistical power), or undertaking research in remote locations. This study describes how VOC may be sampled from skin and recovered from a polydimethylsilicone sampling coupon and analysed by thermal desorption (TD) interfaced to secondary electrospray ionisation (SESI) time-of-flight mass spectrometry (MS) for the high throughput screening of volatile fatty acids (VFAs) from human skin. Analysis times were reduced by 79% compared to gas chromatography-mass spectrometry methods (GC-MS) and limits of detection in the range 300 to 900 pg cm(-2) for VFA skin concentrations were obtained. Using body odour as a surrogate model for clinical testing 10 Filipino participants, 5 high and 5 low odour, were sampled in Manilla and the samples returned to the UK and screened by TD-SESI-MS and TD-GC-MS for malodour precursors with greater than >95% agreement between the two analytical techniques. Eight additional VFAs were also identified by both techniques with chains 4 to 15 carbons long being observed. TD-SESI-MS appears to have significant potential for the high throughput targeted screening of volatile biomarkers in human skin. PMID:24992564

  12. Rapid drug detection in oral samples by porous silicon assisted laser desorption/ionization mass spectrometry.

    PubMed

    Lowe, Rachel D; Guild, Georgia E; Harpas, Peter; Kirkbride, Paul; Hoffmann, Peter; Voelcker, Nicolas H; Kobus, Hilton

    2009-11-01

    The demand for analysis of oral fluid for illicit drugs has arisen with the increased adoption of roadside testing, particularly in countries where changes in legislation allow random roadside testing of drivers for the presence of a palette of illicit drugs such as methamphetamine (MA), 3,4-methylenedioxymethamphetamine (MDMA) and Delta9-tetrahydrocannabinol (THC). Oral samples are currently tested for such drugs at the roadside using an immunoassay-based commercial test kit. Positive roadside tests are sent for confirmatory laboratory analysis, traditionally by means of gas chromatography/mass spectrometry (GC/MS). We present here an alternative rapid analysis technique, porous silicon assisted laser desorption/ionization time-of-flight mass spectrometry (pSi LDI-MS), for the high-throughput analysis of oral fluids. This technique alleviates the need for sample derivatization, requires only sub-microliter sample volumes and allows fast analysis (of the order of seconds). In this study, the application of the technique is demonstrated with real samples from actual roadside testing. The analysis of oral samples resulted in detection of MA and MDMA with no extraction and analysis of THC after ethyl acetate extraction. We propose that, subject to miniaturization of a suitable mass spectrometer, this technique is well suited to underpin the deployment of oral fluid testing in the clinic, workplace and on the roadside. PMID:19844964

  13. Direct analysis of Stevia leaves for diterpene glycosides by desorption electrospray ionization mass spectrometry.

    PubMed

    Jackson, Ayanna U; Tata, Alessandra; Wu, Chunping; Perry, Richard H; Haas, George; West, Leslie; Cooks, R Graham

    2009-05-01

    The analysis of Stevia leaves has been demonstrated without any sample preparation using desorption electrospray ionization (DESI) mass spectrometry. Direct rapid analysis was achieved using minimal amounts of sample ( approximately 0.15 cm x 0.15 cm leaf fragment). Characteristic constituents of the Stevia plant are observed in both the positive and negative ion modes including a series of diterpene 'sweet' glycosides. The presence of the glycosides was confirmed via tandem mass spectrometry analysis using collision-induced dissociation and further supported by exact mass measurements using an LTQ-Orbitrap. The analysis of both untreated and hexane-extracted dry leaves proved that DESI can be successfully used to analyze untreated leaf fragments as identical profiles were obtained from both types of samples. Characterization and semi-quantitative determination of the glycosides was achieved based on the glycoside profile within the full mass spectrum. In addition, the presence of characteristic glycosides in an all-natural commercial Stevia dietary supplement was confirmed. This study provides an example of the application of DESI to direct screening of plant materials, in this case diterpene glycosides. PMID:19381377

  14. Laser desorption/ionization mass spectrometry of diesel particulate matter with charge-transfer complexes.

    PubMed

    Carré, Vincent; Vernex-Loset, Lionel; Krier, Gabriel; Manuelli, Pascal; Muller, Jean-François

    2004-07-15

    Polycyclic aromatic hydrocarbons (PAHs) are often associated with complex matrixes such as exhaust diesel particulate matter (DPM), which complicates their study. In that case, laser desorption/ionization mass spectrometry is one of the techniques which ensures their direct analysis in the solid state. We demonstrate in this paper that the use of charge-transfer pi-complexing agents allows us to selectively detect by Fourier transform ion cyclotron resonance mass spectrometry PAHs adsorbed on diesel particles with high sensitivity. 2,4,7-trinitro-9-fluorenone and 7,7',8,8'-tetracyanoquinodimethane pi-acceptor compounds form charge-transfer complexes with PAHs and prevent their evaporation in the mass spectrometer during analysis. Moreover, the production of PAH molecular ions is dramatically increased by laser irradiation of these complexes at short wavelength (221.7 nm) and low power density (5 x 10(6) W cm(-)(2)). This methodology is applied for the first time to the examination of DPM collected during the new European driving cycle for light-duty vehicles. Differentiation criteria may coherently be assigned to engine operating mode (engine temperature, driving conditions). DPM samples can also be easily distinguished in negative ions according to the high sensitivity of this detection mode to sulfate compounds. PMID:15253632

  15. Exploration of Microplasma Probe Desorption/Ionization Mass Spectrometry (MPPDI-MS) for Biologically Related Analysis.

    PubMed

    Zhao, Zhongjun; Wang, Bo; Duan, Yixiang

    2016-02-01

    To expand the applications of glow discharge microplasma into biological analysis, an innovative ambient ion source for mass spectrometry, microplasma probe desorption/ionization mass spectrometry (MPPDI-MS), has been developed and demonstrated. Electrodes and a sampling tube were creatively combined using a stainless steel syringe needle, and efficient methods of introduction for biological samples in solid, liquid, and gaseous phases like phospholipid and amino acids were specially designed. Based on the active species generated by glow discharge plasma, simplified protonated spectra were obtained without extra solvent spray assistance. The method is easy to operate and versatile and especially has the ability to distinguish the isomeric compounds of ketone and aldehyde. Quantitative results of this method for different biological samples in different phases were also performed well. It was proved that with further improvement, this sensitive and selective analysis using MPPDI-MS with minimal invasiveness will be an ingenious tool in disease diagnosis and single-cell detections in the future. PMID:26758529

  16. Analysis of insect cuticular hydrocarbons using matrix-assisted laser desorption/ionization mass spectrometry.

    PubMed

    Cvacka, Josef; Jiros, Pavel; Sobotník, Jan; Hanus, Robert; Svatos, Ales

    2006-02-01

    Insect cuticular hydrocarbons (CHCs) were probed by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry with a lithium 2,5-dihydroxybenzoate matrix. CHC profiles were obtained for 12 species of diverse insect taxa (termites, ants, a cockroach, and a flesh fly). MALDI spectra revealed the presence of high molecular weight CHCs on the insect cuticle. Hydrocarbons with more than 70 carbon atoms, both saturated and unsaturated, were detected. When compared with gas chromatography/mass spectrometry (GC/MS), MALDI-TOF covered a wider range of CHCs and enabled CHCs of considerably higher molecular weight to be detected. Good congruity between GC/MS and MALDI-TOF was observed in the overlapping region of molecular weights. Moreover, a number of previously undiscovered hydrocarbons were detected in the high mass range beyond the analytical capabilities of current GC/MS instruments. MALDI was shown to hold potential to become an alternative analytical method for insect CHC analyses. The ability of MALDI to discriminate among species varying in the degree of their relatedness was found to be similar to GC/MS. However, neither MALDI-MS nor GC/MS data were able to describe the phylogenetic relationships. PMID:16555131

  17. Detection of trace ink compounds in erased handwritings using electrospray-assisted laser desorption ionization mass spectrometry.

    PubMed

    Kao, Yi-Ying; Cheng, Sy-Chyi; Cheng, Chu-Nian; Shiea, Jentaie; Ho, Hsiu-O

    2014-06-01

    Writings made with erasable pens on paper surfaces can either be rubbed off with an eraser or rendered invisible by changing the temperature of the ink. However, trace ink compounds still remain in the paper fibers even after rubbing or rendering. The detection of these ink compounds from erased handwritings will be helpful in knowing the written history of the paper. In this study, electrospray-assisted laser desorption ionization/mass spectrometry was used to characterize trace ink compounds remaining in visible and invisible ink lines. The ink compounds were desorbed from the paper surface by irradiating the handwritings with a pulsed laser beam; the desorbed analytes were subsequently ionized in an electrospray plume and detected by a quadrupole time-of-flight mass spectrometry mass analyzer. Because of the high spatial resolution of the laser beam, electrospray-assisted laser desorption ionization/mass spectrometry analysis resulted in minimal damage to the sample documents. PMID:24913397

  18. Nanostructured silicon surface modifications for as a selective matrix-free laser desorption/ionization mass spectrometry.

    PubMed

    Tsao, C W; Lin, C H; Cheng, Y C; Chien, C C; Chang, C C; Chen, W Y

    2012-06-01

    Matrix-assisted laser desorption/ionization mass spectrometry is an established soft ionization method that is widely applied to analyze biomolecules. The UV-absorbing organic matrix is essential for biomolecule ionization; however, it also creates matrix background interference, which results in problematic analyses of biomolecules of less than 700 Da. Therefore, this study investigates hydrophilic, hydrophobic cationic, anionic and immobilized metal ion surface chemical modifications to advance nanostructured silicon mass spectrometry performance (nSi-MS). This investigation provides information required for a possible novel mass spectroscopy that combines surface-enhanced and nanostructured silicon surface-assisted laser desorption/ionization mass spectrometry for the selective detection of specific compounds of a mixture. PMID:22531330

  19. Determination of five booster biocides in seawater by stir bar sorptive extraction-thermal desorption-gas chromatography-mass spectrometry.

    PubMed

    Giráldez, I; Chaguaceda, E; Bujalance, M; Morales, E

    2013-01-01

    Stir bar sorptive extraction (SBSE) and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS) have been optimized for the determination of five organic booster biocides (Chlorothalonil, Dichlofluanid, Sea-Nine 211, Irgarol 1051 and TCMTB) in seawater samples. The parameters affecting the desorption and absorption steps were investigated using 10 mL seawater samples. The optimised conditions consisted of an addition of 0.2 g mL(-1) KCl to the sample, which was extracted with 10mm length, 0.5mm film thickness stir bars coated with polydimethylsiloxane (PDMS), and stirred at 900 rpm for 90 min at room temperature (25 °C) in a vial. Desorption was carried out at 280 °C for 5 min under 50 mL min(-1) of helium flow in the splitless mode while maintaining a cryotrapping temperature of 20 °C in the programmed-temperature vaporization (PTV) injector of the GC-MS system. Finally, the PTV injector was ramped to a temperature of 280 °C and the analytes were separated in the GC and detected by MS using the selected-ion monitoring (SIM) mode. The detection limits of booster biocides were found to be in the range of 0.005-0.9 μg L(-1). The regression coefficients were higher than 0.999 for all analytes. The average recovery was higher than 72% (R.S.D.: 7-15%). All these figures of merit were established running samples in triplicate. This simple, accurate, sensitive and selective analytical method may be used for the determination of trace amounts of booster biocides in water samples from marinas. PMID:23246091

  20. Electroless plating of silver nanoparticles on porous silicon for laser desorption/ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Yan, Hong; Xu, Ning; Huang, Wen-Yi; Han, Huan-Mei; Xiao, Shou-Jun

    2009-03-01

    An improved DIOS (desorption ionization on porous silicon) method for laser desorption/ionization mass spectrometry (LDI MS) by electroless plating of silver nanoparticles (AgNPs) on porous silicon (PSi) was developed. By addition of 4-aminothiophenol (4-ATP) into the AgNO3 plating solution, the plating speed can be slowed down and simultaneously 4-ATP self-assembled monolayers (SAMs) on AgNPs (4-ATP/AgNPs) were formed. Both AgNPs and 4-ATP/AgNPs coated PSi substrates present much higher stability, sensitivity and reproducibility for LDI MS than the un-treated porous silicon ones. Their shelf life in air was tested for several weeks to a month and their mass spectra still displayed the same high quality and sensitivity as the freshly prepared ones. And more 4-ATP SAMs partly play a role of matrix to increase the ionization efficiency. A small organic molecule of tetrapyridinporphyrin (TPyP), oligomers of polyethylene glycol (PEG 400 and 2300), and a peptide of oxytocin were used as examples to demonstrate the feasibility of the silver-plated PSi as a matrix-free-like method for LDI MS. This approach can obtain limits of detection to femtomoles for TPyP, subpicomoles for oxytocin, and picomoles for PEG 400 and 2300, comparable to the traditional matrix method and much better than the DIOS method. It simplifies the sample preparation as a matrix-free-like method without addition of matrix molecules and homogenizes the sample spread over the spot for better and more even mass signals.

  1. Thin-layer chromatography/desorption electrospray ionization mass spectrometry: investigation of goldenseal alkaloids.

    PubMed

    Van Berkel, Gary J; Tomkins, Bruce A; Kertesz, Vilmos

    2007-04-01

    Desorption electrospray ionization mass spectrometry was investigated as a means to qualitatively identify and to quantify analytes directly from developed normal-phase thin-layer chromatography plates. The atmospheric sampling capillary of a commercial ion trap mass spectrometer was extended to permit sampling and ionization of analytes in bands separated on intact TLC plates (up to 10 cmx10 cm). A surface positioning software package and the appropriate hardware enabled computer-controlled surface scanning along the length of development lanes or at fixed Rf value across the plates versus the stationary desorption electrospray emitter. Goldenseal (Hydrastis canadensis) and related alkaloids and commercial dietary supplements were used as standards and samples. Alkaloid standards and samples were spotted and separated on aluminum- or glass-backed plates using established literature methods. The mass spectral signal levels as a function of desorption spray solvent were investigated with acetonitrile proving superior to methanol. The detection levels (approximately 5 ng each or 14-28 pmol) in mass spectral full-scan mode were determined statistically from the calibration curves (2.5-100 pmol) for the standards berberine, palmatine, and hydrastinine spotted as a mixture and separated on the plates. Qualitative screening of the major alkaloids present in six different over-the-counter "goldenseal" dietary supplements was accomplished by obtaining full-scan mass spectra during surface scans along the development lane in the direction of increasing Rf value. In one sample, alkaloids were detected that strongly suggested the presence of at least one additional herb undeclared on the product label. These same data indicated the misidentification of one of the alkaloids in the TLC literature. Quantities of the alkaloids present in two of the samples determined using the mass spectral data were in reasonable agreement with the label values, indicating the quantitative

  2. A Combined Desorption Ionization by Charge Exchange (DICE) and Desorption Electrospray Ionization (DESI) Source for Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Chan, Chang-Ching; Bolgar, Mark S.; Miller, Scott A.; Attygalle, Athula B.

    2011-01-01

    A source that couples the desorption ionization by charge exchange (DICE) and desorption electrospray ionization (DESI) techniques together was demonstrated to broaden the range of compounds that can be analyzed in a single mass spectrometric experiment under ambient conditions. A tee union was used to mix the spray reagents into a partially immiscible blend before this mixture was passed through a conventional electrospray (ES) probe capillary. Using this technique, compounds that are ionized more efficiently by the DICE method and those that are ionized better with the DESI procedure could be analyzed simultaneously. For example, hydroquinone, which is not detected when subjected to DESI-MS in the positive-ion generation mode, or the sodium adduct of guaifenesin, which is not detected when examined by DICE-MS, could both be detected in one experiment when the two techniques were combined. The combined technique was able to generate the molecular ion, proton and metal adduct from the same compound. When coupled to a tandem mass spectrometer, the combined source enabled the generation of product ion spectra from the molecular ion and the [M + H]+ or [M + metal]+ ions of the same compound without the need to physically change the source from DICE to DESI. The ability to record CID spectra of both the molecular ion and adduct ions in a single mass spectrometric experiment adds a new dimension to the array of mass spectrometric methods available for structural studies.

  3. A combined desorption ionization by charge exchange (DICE) and desorption electrospray ionization (DESI) source for mass spectrometry.

    PubMed

    Chan, Chang-Ching; Bolgar, Mark S; Miller, Scott A; Attygalle, Athula B

    2011-01-01

    A source that couples the desorption ionization by charge exchange (DICE) and desorption electrospray ionization (DESI) techniques together was demonstrated to broaden the range of compounds that can be analyzed in a single mass spectrometric experiment under ambient conditions. A tee union was used to mix the spray reagents into a partially immiscible blend before this mixture was passed through a conventional electrospray (ES) probe capillary. Using this technique, compounds that are ionized more efficiently by the DICE method and those that are ionized better with the DESI procedure could be analyzed simultaneously. For example, hydroquinone, which is not detected when subjected to DESI-MS in the positive-ion generation mode, or the sodium adduct of guaifenesin, which is not detected when examined by DICE-MS, could both be detected in one experiment when the two techniques were combined. The combined technique was able to generate the molecular ion, proton and metal adduct from the same compound. When coupled to a tandem mass spectrometer, the combined source enabled the generation of product ion spectra from the molecular ion and the [M + H](+) or [M + metal](+) ions of the same compound without the need to physically change the source from DICE to DESI. The ability to record CID spectra of both the molecular ion and adduct ions in a single mass spectrometric experiment adds a new dimension to the array of mass spectrometric methods available for structural studies. PMID:21472555

  4. Mapping Lipid Alterations in Traumatically Injured Rat Spinal Cord by Desorption Electrospray Ionization Imaging Mass Spectrometry

    PubMed Central

    Girod, Marion; Shi, Yunzhou; Cheng, Ji-Xin; Cooks, R. Graham

    2010-01-01

    Desorption electrospray ionization (DESI) mass spectrometry is used in an imaging mode to interrogate the lipid profiles of 15 µm thin tissues cross sections of injured rat spinal cord and normal healthy tissue. Increased relative intensities of fatty acids, diacylglycerols and lysolipids (between +120% and +240%) as well as a small decrease in intensities of lipids (−30%) were visualized in the lesion epi-center and adjacent areas after spinal cord injury. This indicates the hydrolysis of lipids during the demyelination process due to activation of phospholipase A2 enzyme. In addition, signals corresponding to oxidative degradation products, such as prostaglandin and hydroxyeicosatetraenoic acid, exhibited increased signal intensity by a factor of two in the negative ion mode in lesions relative to the normal healthy tissue. Analysis of malondialdehyde, a product of lipid peroxidation and marker of oxidative stress, was accomplished in the ambient environment using reactive DESI mass spectrometry imaging. This was achieved by electrospraying reagent solution containing dinitrophenylhydrazine as high velocity charged droplets onto the tissue section. The hydrazine reacts selectively and rapidly with the carbonyl groups of malondialdehyde and signal intensity of twice the intensity was detected in the lesions compared to healthy spinal cord. With a small amount of tissue sample, DESI-MS imaging provides information on the composition and distribution of specific compounds (limited by the occurrence of isomeric lipids with very similar fragmentation patterns) in lesions after spinal cord injury in comparison with normal healthy tissue allowing identification of the extent of the lesion and its repair. PMID:21142140

  5. Investigation of some biologically relevant redox reactions using electrochemical mass spectrometry interfaced by desorption electrospray ionization

    PubMed Central

    Lu, Mei; Wolff, Chloe; Cui, Weidong

    2013-01-01

    Recently we have shown that, as a versatile ionization technique, desorption electrospray ionization (DESI) can serve as a useful interface to combine electrochemistry (EC) with mass spectrometry (MS). In this study, the EC/DESI-MS method has been further applied to investigate some aqueous phase redox reactions of biological significance, including the reduction of peptide disulfide bonds and nitroaromatics as well as the oxidation of phenothiazines. It was found that knotted/enclosed disulfide bonds in the peptides apamin and endothelin could be electrochemically cleaved. Subsequent tandem MS analysis of the resulting reduced peptide ions using collision-induced dissociation (CID) and electron-capture dissociation (ECD) gave rise to extensive fragment ions, providing a fast protocol for sequencing peptides with complicated disulfide bond linkages. Flunitrazepam and clonazepam, a class of nitroaromatic drugs, are known to undergo reduction into amines which was proposed to involve nitroso and N-hydroxyl intermediates. Now in this study, these corresponding intermediate ions were successfully intercepted and their structures were confirmed by CID. This provides mass spectrometric evidence for the mechanism of the nitro to amine conversion process during nitroreduction, an important redox reaction involved in carcinogenesis. In addition, the well-known oxidation reaction of chlorpromazine was also examined. The putative transient one-electron transfer product, the chlorpromazine radical cation (m/z 318), was captured by MS, for the first time, and its structure was also verified by CID. In addition to these observations, some features of the DESI-interfaced electrochemical mass spectrometry were discussed, such as simple instrumentation and the lack of background signal. These results further demonstrate the feasibility of EC/DESI-MS for the study of the biology-relevant redox chemistry and would find applications in proteomics and drug development research. PMID

  6. Online Investigation of Aqueous-Phase Electrochemical Reactions by Desorption Electrospray Ionization Mass Spectrometry.

    PubMed

    Lu, Mei; Liu, Yong; Helmy, Roy; Martin, Gary E; Dewald, Howard D; Chen, Hao

    2015-10-01

    Electrochemistry (EC) combined with mass spectrometry (MS) is a powerful tool for elucidation of electrochemical reaction mechanisms. However, direct online analysis of electrochemical reaction in aqueous phase was rarely explored. This paper presents the online investigation of several electrochemical reactions with biological relevance in the aqueous phase, such as nitrosothiol reduction, carbohydrate oxidation, and carbamazepine oxidation using desorption electrospray ionization mass spectrometry (DESI-MS). It was found that electroreduction of nitrosothiols [e.g., nitrosylated insulin B (13-23)] leads to free thiols by loss of NO, as confirmed by online MS analysis for the first time. The characteristic mass shift of 29 Da and the reduced intensity provide a quick way to identify nitrosylated species. Equally importantly, upon collision-induced dissociation (CID), the reduced peptide ion produces more fragment ions than its nitrosylated precursor ion (presumably the backbone fragmentation cannot compete with the facile NO loss for the precursor ion), thus facilitating peptide sequencing. In the case of saccharide oxidation, it was found that glucose undergoes electro-oxidation to produce gluconic acid at alkaline pH, but not at neutral and acidic pHs. Such a pH-dependent electrochemical behavior was also observed for disaccharides such as maltose and cellobiose. Upon electrochemical oxidation, carbamazepine was found to undergo ring contraction and amide bond cleavage, which parallels the oxidative metabolism observed for this drug in leucocytes. The mechanistic information of these redox reactions revealed by EC/DESI-MS would be of value in nitroso-proteome research and carbohydrate/drug metabolic studies. PMID:26242804

  7. Atmospheric pressure laser-induced acoustic desorption chemical ionization mass spectrometry for analysis of saturated hydrocarbons.

    PubMed

    Nyadong, Leonard; Quinn, John P; Hsu, Chang S; Hendrickson, Christopher L; Rodgers, Ryan P; Marshall, Alan G

    2012-08-21

    We present atmospheric pressure laser-induced acoustic desorption chemical ionization (AP/LIAD-CI) with O(2) carrier/reagent gas as a powerful new approach for the analysis of saturated hydrocarbon mixtures. Nonthermal sample vaporization with subsequent chemical ionization generates abundant ion signals for straight-chain, branched, and cycloalkanes with minimal or no fragmentation. [M - H](+) is the dominant species for straight-chain and branched alkanes. For cycloalkanes, M(+•) species dominate the mass spectrum at lower capillary temperature (<100 °C) and [M - H](+) at higher temperature (>200 °C). The mass spectrum for a straight-chain alkane mixture (C(21)-C(40)) shows comparable ionization efficiency for all components. AP/LIAD-CI produces molecular weight distributions similar to those for gel permeation chromatography for polyethylene polymers, Polywax 500 and Polywax 655. Coupling of the technique to Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) for the analysis of complex hydrocarbon mixtures provides unparalleled mass resolution and accuracy to facilitate unambiguous elemental composition assignments, e.g., 1754 peaks (rms error = 175 ppb) corresponding to a paraffin series (C(12)-C(49), double-bond equivalents, DBE = 0) and higher DBE series corresponding to cycloparaffins containing one to eight rings. Isoabundance-contoured plots of DBE versus carbon number highlight steranes (DBE = 4) of carbon number C(27)-C(30) and hopanes of C(29)-C(35) (DBE = 5), with sterane-to-hopane ratio in good agreement with field ionization (FI) mass spectrometry analysis, but performed at atmospheric pressure. The overall speciation of nonpolar, aliphatic hydrocarbon base oil species offers a promising diagnostic probe to characterize crude oil and its products. PMID:22881221

  8. Online Investigation of Aqueous-Phase Electrochemical Reactions by Desorption Electrospray Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Lu, Mei; Liu, Yong; Helmy, Roy; Martin, Gary E.; Dewald, Howard D.; Chen, Hao

    2015-08-01

    Electrochemistry (EC) combined with mass spectrometry (MS) is a powerful tool for elucidation of electrochemical reaction mechanisms. However, direct online analysis of electrochemical reaction in aqueous phase was rarely explored. This paper presents the online investigation of several electrochemical reactions with biological relevance in the aqueous phase, such as nitrosothiol reduction, carbohydrate oxidation, and carbamazepine oxidation using desorption electrospray ionization mass spectrometry (DESI-MS). It was found that electroreduction of nitrosothiols [e.g., nitrosylated insulin B (13-23)] leads to free thiols by loss of NO, as confirmed by online MS analysis for the first time. The characteristic mass shift of 29 Da and the reduced intensity provide a quick way to identify nitrosylated species. Equally importantly, upon collision-induced dissociation (CID), the reduced peptide ion produces more fragment ions than its nitrosylated precursor ion (presumably the backbone fragmentation cannot compete with the facile NO loss for the precursor ion), thus facilitating peptide sequencing. In the case of saccharide oxidation, it was found that glucose undergoes electro-oxidation to produce gluconic acid at alkaline pH, but not at neutral and acidic pHs. Such a pH-dependent electrochemical behavior was also observed for disaccharides such as maltose and cellobiose. Upon electrochemical oxidation, carbamazepine was found to undergo ring contraction and amide bond cleavage, which parallels the oxidative metabolism observed for this drug in leucocytes. The mechanistic information of these redox reactions revealed by EC/DESI-MS would be of value in nitroso-proteome research and carbohydrate/drug metabolic studies.

  9. Characterization of Coordination Complexes by Desorption Electrospray Mass Spectrometry with a Capillary Target

    SciTech Connect

    Gary S. Groenewold; Anthony D. Appelhans; Michael E. McIlwain; Garold L. Gresham

    2011-03-01

    Metal coordination complexes were formed directly from liquid surfaces using desorption electrospray ionization (DESI) mass spectrometry. The approach is attractive because it separates complexities of ESI spray droplet formation from delivery of the analyte solution, and thereby gets around difficulty resulting from alteration of the spray process by changes in solution chemistry. Cs+, Ba2+, and La3+ coordination complexes were formed using 18-crown-6 (18c6) and triethylphosphate (TEP) as ligands (L), that had the general formula [Mn+(NO3-)n-1(L)m]+. Formation of singly charged cation complexes was preferred, with charge reduction at the metal site accomplished by attachment of nitrate. Using TEP as a model phosphoryl ligand, alkali metals coordinate with up to three ligands, with Cs+ preferring fewer than Na+. Ba2+ and La3+ are formed as ion pair complexes [Ba(NO3)]+ and [La(NO3)2]+, and both will coordinate with up to four TEP ligands. Using 18c6, Cs+ forms a bis-ligand complex. In contrast, [Ba(NO3)]+ prefers a single 18c6 ligand, while La forms mainly [La(NO3)2(18c6)]+, for which DFT calculations suggested a structure in which the nitrate ligands occupy pseudo-axial positions on opposing sides of the crown. Lower abundances of bis-18c6 complexes were also formed together with doubly charged [La(NO3)(18c6)n]2+ complexes (n = 2 – 4). The results suggest an alternative strategy for probing metal speciation in solution that is less perturbed by the droplet formation and ionization mechanisms operating in conventional electrospray ionization mass spectrometry.

  10. Non-traditional applications of laser desorption/ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    McAlpin, Casey R.

    Seven studies were carried out using laser desorption/ionization mass spectrometry (LDI MS) to develop enhanced methodologies for a variety of analyte systems by investigating analyte chemistries, ionization processes, and elimination of spectral interferences. Applications of LDI and matrix assisted laser/desorption/ionization (MALDI) have been previously limited by poorly understood ionization phenomena, and spectral interferences from matrices. Matrix assisted laser desorption ionization MS is well suited to the analysis of proteins. However, the proteins associated with bacteriophages often form complexes which are too massive for detection with a standard MALDI mass spectrometer. As such, methodologies for pretreatment of these samples are discussed in detail in the first chapter. Pretreatment of bacteriophage samples with reducing agents disrupted disulfide linkages and allowed enhanced detection of bacteriophage proteins. The second chapter focuses on the use of MALDI MS for lipid compounds whose molecular mass is significantly less than the proteins for which MALDI is most often applied. The use of MALDI MS for lipid analysis presented unique challenges such as matrix interference and differential ionization efficiencies. It was observed that optimization of the matrix system, and addition of cationization reagents mitigated these challenges and resulted in an enhanced methodology for MALDI MS of lipids. One of the challenges commonly encountered in efforts to expand MALDI MS applications is as previously mentioned interferences introduced by organic matrix molecules. The third chapter focuses on the development of a novel inorganic matrix replacement system called metal oxide laser ionization mass spectrometry (MOLI MS). In contrast to other matrix replacements, considerable effort was devoted to elucidating the ionization mechanism. It was shown that chemisorption of analytes to the metal oxide surface produced acidic adsorbed species which then

  11. Direct analysis of ethylenediaminetetraacetic acid (EDTA) on concrete by reactive-desorption electrospray ionization mass spectrometry.

    PubMed

    Lebeau, D; Reiller, P E; Lamouroux, C

    2015-01-01

    Analysis of organic ligands such as ethylenediaminetetraacetic acid (EDTA) is today an important challenge due to their ability to increase the mobility of radionuclides and metals. Reactive desorption electrospray ionization mass spectrometry (reactive-DESI-MS) was used for direct analysis of EDTA on concrete samples. EDTA forms complexes and those with Fe(III) ions are among the most thermodynamically favored. This complexing capacity was used to improve the specific detection of EDTA directly on a concrete matrix by doping the solvent spray of DESI with a solution of FeCl3 to selectively create the complex between EDTA and Fe(III). Thus, EDTA sensitivity was largely improved by two orders of magnitude with reactive-DESI-MS experiments thanks to the specific detection of EDTA as a [EDTA-4H+Fe(III)](-) complex. The proof of principle that reactive DESI can be applied to concrete samples to detect EDTA has been demonstrated. Its capacity for semi-quantitative determination and localization of EDTA under ambient conditions and with very little sample preparation, minimizing sample manipulations and solvent volumes, two important conditions for the development of new methodologies in the field of analytical chemistry, has been shown. PMID:25476391

  12. Combination of HPLC and 252-Cf plasma desorption mass spectrometry for identifying composition of ginseng tinctures.

    PubMed

    Elkin, Y N; Makhankov, V V; Uvarova, N L; Bondarenko, P V; Zubarev, R A; Knysh, A N

    1993-03-01

    The 252-Cf plasma desorption mass spectrometry (252-Cf PDMS) determination or confirmation of the ginsenoside saponins has been proposed to investigate the composition of high performance liquid chromatography (HPLC) peaks of ginseng tinctures and galenic preparations. That ionization technique is well suitable for the analysis of natural mixtures of these saponins. The 252-Cf PD mass spectra of standard ginsenosides Rb1, Rb2, Rc, Re, Rg1, Rd, NG-R2, Z-R1 contain the peaks of two types of ions, namely, molecular adduct ions (MAI) and aglycone ions. By mass the latter may be referred to either protopanaxadiol or protopanaxatriol. The masses of MAI and aglycone ions are determined by the carbohydrate chains. The collected HPLC fractions of P ginseng tincture can be tested for content of ginsenosides. After studying two MAI peaks from the 252-Cf PD mass spectra of the basic ginsenosides, an example of distinction between two galenic preparations from different Panax has been shown. PMID:8352021

  13. Application of desorption electrospray ionization mass spectrometry imaging in breast cancer margin analysis

    PubMed Central

    Calligaris, David; Caragacianu, Diana; Liu, Xiaohui; Norton, Isaiah; Thompson, Christopher J.; Richardson, Andrea L.; Golshan, Mehra; Easterling, Michael L.; Santagata, Sandro; Dillon, Deborah A.; Jolesz, Ferenc A.; Agar, Nathalie Y. R.

    2014-01-01

    Distinguishing tumor from normal glandular breast tissue is an important step in breast-conserving surgery. Because this distinction can be challenging in the operative setting, up to 40% of patients require an additional operation when traditional approaches are used. Here, we present a proof-of-concept study to determine the feasibility of using desorption electrospray ionization mass spectrometry imaging (DESI-MSI) for identifying and differentiating tumor from normal breast tissue. We show that tumor margins can be identified using the spatial distributions and varying intensities of different lipids. Several fatty acids, including oleic acid, were more abundant in the cancerous tissue than in normal tissues. The cancer margins delineated by the molecular images from DESI-MSI were consistent with those margins obtained from histological staining. Our findings prove the feasibility of classifying cancerous and normal breast tissues using ambient ionization MSI. The results suggest that an MS-based method could be developed for the rapid intraoperative detection of residual cancer tissue during breast-conserving surgery. PMID:25246570

  14. Desorption Electrospray Ionization Mass Spectrometry Reveals Lipid Metabolism of Individual Oocytes and Embryos

    PubMed Central

    González-Serrano, Andrés Felipe; Pirro, Valentina; Ferreira, Christina R.; Oliveri, Paolo; Eberlin, Livia S.; Heinzmann, Julia; Lucas-Hahn, Andrea; Niemann, Heiner; Cooks, Robert Graham

    2013-01-01

    Alteration of maternal lipid metabolism early in development has been shown to trigger obesity, insulin resistance, type 2 diabetes and cardiovascular diseases later in life in humans and animal models. Here, we set out to determine (i) lipid composition dynamics in single oocytes and preimplantation embryos by high mass resolution desorption electrospray ionization mass spectrometry (DESI-MS), using the bovine species as biological model, (ii) the metabolically most relevant lipid compounds by multivariate data analysis and (iii) lipid upstream metabolism by quantitative real-time PCR (qRT-PCR) analysis of several target genes (ACAT1, CPT 1b, FASN, SREBP1 and SCAP). Bovine oocytes and blastocysts were individually analyzed by DESI-MS in both positive and negative ion modes, without lipid extraction and under ambient conditions, and were profiled for free fatty acids (FFA), phospholipids (PL), cholesterol-related molecules, and triacylglycerols (TAG). Principal component analysis (PCA) and linear discriminant analysis (LDA), performed for the first time on DESI-MS fused data, allowed unequivocal discrimination between oocytes and blastocysts based on specific lipid profiles. This analytical approach resulted in broad and detailed lipid annotation of single oocytes and blastocysts. Results of DESI-MS and transcript regulation analysis demonstrate that blastocysts produced in vitro and their in vivo counterparts differed significantly in the homeostasis of cholesterol and FFA metabolism. These results should assist in the production of viable and healthy embryos by elucidating in vivo embryonic lipid metabolism. PMID:24073231

  15. Laser desorption ionization time-of-flight mass spectrometry of nitrated polycyclic aromatic hydrocarbons

    SciTech Connect

    Bezabeth, D.Z.; McCauley, E.M.; Kelly, P.B.; Jones, A.D.

    1994-12-31

    Polycyclic aromatic hydrocarbon (PAH) are of interest to the environmental community due to their ubiquitous presence and the carcinogenic activity of many members of this class of compounds. Recent attention has been focused on nitro-substituted PAH (nitro-PAH) because of their demonstrated mutagenic and carcinogenic activities. Nitro-PAH are found in diesel exhaust, urban air particulates, coal fly ash, and cigarette smoke. The concentration of nitro-PAH in the environment is typically one to two orders of magnitude less than the unsubstituted PAH. However, the biological activity of nitro-PAH is several orders of magnitude greater than the unsubstituted PAH. Hence, there is a need for an analytical technique which combines sensitivity as well as selectivity for nitro-PAH to allow detection of nitro-PAH over the large background of PAH in the environment. This laboratory is presently investigating the use of laser desorption ionization time-of-flight mass spectrometry as a screening method for nitro-PAH. Previous work in this laboratory examined the positive ion spectra of several nitro-PAH. Weak molecular ion peaks were observed, however, the majority of the detected ions were low mass fragments. The unsubstituted PAH were also found to produce intense positive molecular ion signals in contrast to the very weak molecular signals from the nitro-PAH. Thus, identification of the individual nitro-PAH in an environmental sample would be difficult using only the positive ion spectra.

  16. Metabolic Profiling Directly from the Petri Dish Using Nanospray Desorption Electrospray Ionization Imaging Mass Spectrometry

    SciTech Connect

    Watrous, Jeramie D.; Roach, Patrick J.; Heath, Brandi S.; Alexandrov, Theodore; Laskin, Julia; Dorrestein, Pieter C.

    2013-11-05

    Understanding molecular interaction pathways in complex biological systems constitutes a treasure trove of knowledge that might facilitate the specific, chemical manipulation of the countless microbiological systems that occur throughout our world. However, there is a lack of methodologies that allow the direct investigation of chemical gradients and interactions in living biological systems, in real time. Here, we report the use of nanospray desorption electrospray ionization (nanoDESI) imaging mass spectrometry for in vivo metabolic profiling of living bacterial colonies directly from the Petri dish with absolutely no sample preparation needed. Using this technique, we investigated single colonies of Shewanella oneidensis MR-1, Bacillus subtilis 3610, and Streptomyces coelicolor A3(2) as well as a mixed biofilm of S. oneidensis MR-1 and B. subtilis 3610. Data from B. subtilis 3610 and S. coelicolor A3(2) provided a means of validation for the method while data from S. oneidensis MR-1 and the mixed biofilm showed a wide range of compounds that this bacterium uses for the dissimilatory reduction of extracellular metal oxides, including riboflavin, iron-bound heme and heme biosynthetic intermediates, and the siderophore putrebactin.

  17. New strategies for characterizing ancient proteins using matrix-assisted laser desorption ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Ostrom, Peggy H.; Schall, Michael; Gandhi, Hasand; Shen, Tun-Li; Hauschka, Peter V.; Strahler, John R.; Gage, Douglas A.

    2000-03-01

    Structural characterization of ancient proteins is confounded by the small quantity of material remaining in fossils, difficulties in purification, and the inability to obtain sequence information by classical Edman degradation. We present a microbore reversed phase high performance liquid chromatography (rpHPLC) method for partial purification of small quantities (picomoles) of the bone protein osteocalcin (OC) and subsequent characterization of this material by matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). The presence of OC in the modern and ancient samples was suggested by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and radioimmunoassay (RIA). The SDS-PAGE of material isolated from 800 yr BP and 10,000 yr BP bones demonstrates a band consistent with the molecular weight of OC and the RIA indicated OC in concentrations of 0.2 to 450ng/mg of bone for samples between 800 and 53,000 yr BP. In modern samples, we demonstrate the use of MALDI-MS to confirm the molecular weight of intact OC and to sequence OC via peptide mass mapping and a novel derivatization approach with post-source decay analysis. MALDI-MS data for three ancient samples with RIA-confirmed osteocalcin (800 yr BP, 10,000 yr BP and 53,000 yr BP) indicate peaks with a molecular mass within the range of modern OC.

  18. Sequence analysis of chitooligosaccharides by matrix-assisted laser desorption ionization postsource decay mass spectrometry.

    PubMed

    Bahrke, Sven; Einarsson, Jon M; Gislason, Johannes; Haebel, Sophie; Letzel, Matthias C; Peter-Katalinić, Jasna; Peter, Martin G

    2002-01-01

    Chitin/chitosan oligosaccharides composed of 2-acetamido-2-deoxy-D-glucopyranose (GlcNAc) and/or 2-amino-2-deoxy-D-glucopyranose (GlcN) were prepared by chemical degradation of chitin or chitosan and separated by gel permeation chromatography. Oligosaccharides obtained after enzymatic hydrolysis of chitosan [F(A) 0.19] with a fungal chitinase were derivatized by reductive amination with 2-aminoacridone and sequenced by matrix-assisted laser desorption ionization time-of-flight postsource decay (PSD) mass spectrometry (MS). The sequence of a trimer, D1A2, was established as D-A-A. The composition of a hexamer D3A3 was ca. 65% D-A-D-D-A-A and 35% D-D-A-D-A-A. The PSD MS of a nonamer D5A4-amac revealed four isobaric species D-X-Y-D-X-Y-D-A-A, where A is GlcNAc, D is GlcN, and X and Y (X not equal Y) are mutually either D or A. This structure motif was also observed in a dodecamer D7A5 which was composed of eight isobaric sequences of the general formula (D-X-Y)(3)-D-A-A. PMID:12099813

  19. Atomic Force Microscope Controlled Topographical Imaging and Proximal Probe Thermal Desorption/Ionization Mass Spectrometry Imaging

    SciTech Connect

    Ovchinnikova, Olga S; Kjoller, Kevin; Hurst, Gregory {Greg} B; Pelletier, Dale A; Van Berkel, Gary J

    2014-01-01

    This paper reports on the development of a hybrid atmospheric pressure atomic force microscopy/mass spectrometry imaging system utilizing nano-thermal analysis probes for thermal desorption surface sampling with subsequent atmospheric pressure chemical ionization and mass analysis. The basic instrumental setup and the general operation of the system were discussed and optimized performance metrics were presented. The ability to correlate topographic images of a surface with atomic force microscopy and a mass spectral chemical image of the same surface, utilizing the same probe without moving the sample from the system, was demonstrated. Co-registered mass spectral chemical images and atomic force microscopy topographical images were obtained from inked patterns on paper as well as from a living bacterial colony on an agar gel. Spatial resolution of the topography images based on pixel size (0.2 m x 0.8 m) was better than the resolution of the mass spectral images (2.5 m x 2.0 m), which were limited by current mass spectral data acquisition rate and system detection levels.

  20. Thermal desorption gas chromatography with mass spectrometry study of outgassing from polymethacrylimide foam (Rohacell®).

    PubMed

    Carrasco-Correa, Enrique J; Herrero-Martínez, José M; Consuegra, Lina; Ramis-Ramos, Guillermo; Sanz, Rafael Mata; Martínez, Benito Gimeno; Esbert, Vicente E Boria; García-Baquero, David Raboso

    2015-09-01

    Polymethacrylimide foams are used as light structural materials in outer-space devices; however, the foam closed cells contain volatile compounds that are outgassed even at low temperatures. These compounds ignite as plasmas under outer-space radiation and the intense radio-frequency fields used in communications. Since plasmas may cause spacecraft fatal events, the conditions in which they are ignited should be investigated. Therefore, qualitative and quantitative knowledge about polymethacrylimide foam outgassing should be established. Using thermogravimetric analysis, weight losses reached 3% at ca. 200°C. Thermal desorption gas chromatography with mass spectrometry detection was used to study the offgassed compounds. Using successive 4 min heating cycles at 125°C, each one corresponding to an injection, significant amounts of nitrogen (25.3%), water (2.6%), isobutylene (11.3%), tert-butanol (2.9%), 1-propanol (11.9%), hexane (25.3%), propyl methacrylate (1.4%), higher hydrocarbons (11.3%), fatty acids (2.2%) and their esters (1.3%), and other compounds were outgassed. Other compounds were observed during the main stage of thermal destruction (220-280°C). A similar study at 175°C revealed the extreme difficulty in fully outgassing polar compounds from polymethacrylimide foams by baking and showed the different compositions of the offgassed atmosphere that can be expected in the long term. PMID:26106018

  1. Laser desorption time-of-flight mass spectrometry of ultraviolet photo-processed ices

    SciTech Connect

    Paardekooper, D. M. Bossa, J.-B.; Isokoski, K.; Linnartz, H.

    2014-10-01

    A new ultra-high vacuum experiment is described that allows studying photo-induced chemical processes in interstellar ice analogues. MATRI²CES - a Mass Analytical Tool to study Reactions in Interstellar ICES applies a new concept by combining laser desorption and time-of-flight mass spectrometry with the ultimate goal to characterize in situ and in real time the solid state evolution of organic compounds upon UV photolysis for astronomically relevant ice mixtures and temperatures. The performance of the experimental setup is demonstrated by the kinetic analysis of the different photoproducts of pure methane (CH₄) ice at 20 K. A quantitative approach provides formation yields of several new species with up to four carbon atoms. Convincing evidence is found for the formation of even larger species. Typical mass resolutions obtained range from M/ΔM ~320 to ~400 for CH₄ and argon, respectively. Additional tests show that the typical detection limit (in monolayers) is ⩽0.02 ML, substantially more sensitive than the regular techniques used to investigate chemical processes in interstellar ices.

  2. Tracing origins of complex pharmaceutical preparations using surface desorption atmospheric pressure chemical ionization mass spectrometry.

    PubMed

    Zhang, Xinglei; Jia, Bin; Huang, Keke; Hu, Bin; Chen, Rong; Chen, Huanwen

    2010-10-01

    A novel strategy to trace the origins of commercial pharmaceutical products has been developed based on the direct chemical profiling of the pharmaceutical products by surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS). Besides the unambiguous identification of active drug components, various compounds present in the matrixes are simultaneously detected without sample pretreatment, providing valuable information for drug quality control and origin differentiation. Four sources of commercial amoxicillin products made by different manufacturers have been successfully differentiated. This strategy has been extended to secerning six sources of Liuwei Dihuang Teapills, which are herbal medicine preparations with extremely complex matrixes. The photolysis status of chemical drug products and the inferior natural herd medicine products prepared with different processes (e.g., extra heating) were also screened using the method reported here. The limit of detection achieved in the MS/MS experiments was estimated to be 1 ng/g for amoxicillin inside the capsule product. Our experimental data demonstrate that DAPCI-MS is a useful tool for rapid pharmaceutical analysis, showing promising perspectives for tracking the entire pharmaceutical supply chain to prevent counterfeit intrusions. PMID:20809628

  3. Detection of malaria parasites in blood by laser desorption mass spectrometry.

    PubMed

    Demirev, P A; Feldman, A B; Kongkasuriyachai, D; Scholl, P; Sullivan, D; Kumar, N

    2002-07-15

    A novel method for the in vitro detection of the protozoan Plasmodium, the causative agent of malaria, has been developed. It comprises a protocol for cleanup of whole blood samples, followed by direct ultraviolet laser desorption (LD) time-of-flight mass spectrometry. Intense ion signals are observed from intact ferriprotoporphyrin IX (heme), sequestered by malaria parasites during their growth in human red blood cells. The LD mass spectrum of the heme is structure-specific, and the signal intensities are correlated with the sample parasitemia (number of parasites per unit volume of blood). Parasitemia levels on the order of 10 parasites/microL blood can be unambiguously detected by this method. Consideration of laser beam parameters (spot size, rastering across the sample surface) and actual sample consumption suggests that the detection limits can be further improved by at least an order of magnitude. The influence of experimental factors, such as desorbed ion polarity, laser exposure and fluence, sample size, and parasite growth stage, on the threshold for parasite detection is also addressed. PMID:12139027

  4. An Automated Platform for High-Resolution Tissue Imaging Using Nanospray Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Lanekoff, Ingela T.; Heath, Brandi S.; Liyu, Andrey V.; Thomas, Mathew; Carson, James P.; Laskin, Julia

    2012-10-02

    An automated platform has been developed for acquisition and visualization of mass spectrometry imaging (MSI) data using nanospray desorption electrospray ionization (nano-DESI). The new system enables robust operation of the nano-DESI imaging source over many hours. This is achieved by controlling the distance between the sample and the probe by mounting the sample holder onto an automated XYZ stage and defining the tilt of the sample plane. This approach is useful for imaging of relatively flat samples such as thin tissue sections. Custom software called MSI QuickView was developed for visualization of large data sets generated in imaging experiments. MSI QuickView enables fast visualization of the imaging data during data acquisition and detailed processing after the entire image is acquired. The performance of the system is demonstrated by imaging rat brain tissue sections. High resolution mass analysis combined with MS/MS experiments enabled identification of lipids and metabolites in the tissue section. In addition, high dynamic range and sensitivity of the technique allowed us to generate ion images of low-abundance isobaric lipids. High-spatial resolution image acquired over a small region of the tissue section revealed the spatial distribution of an abundant brain metabolite, creatine, in the white and gray matter that is consistent with the literature data obtained using magnetic resonance spectroscopy.

  5. Thin-layer chromatography and mass spectrometry coupled using desorption electrospray ionization.

    PubMed

    Van Berkel, Gary J; Ford, Michael J; Deibel, Michael A

    2005-03-01

    Desorption electrospray ionization (DESI) was demonstrated as a means to couple thin-layer chromatography (TLC) with mass spectrometry. The experimental setup and its optimization are described. Development lanes were scanned by moving the TLC plate under computer control while directing the stationary DESI emitter charged droplet plume at the TLC plate surface. Mass spectral data were recorded in either selected reaction monitoring mode or in full scan ion trap mode using a hybrid triple quadrupole linear ion trap mass spectrometer. Fundamentals and practical applications of the technique were demonstrated in positive ion mode using selected reaction monitoring detection of rhodamine dyes separated on hydrophobic reversed-phase C8 plates and reversed-phase C2 plates, in negative ion full scan mode using a selection of FD&C dyes separated on a wettable reversed-phase C18 plate, and in positive ion full scan mode using a mixture of aspirin, acetaminophen, and caffeine from an over-the-counter pain medication separated on a normal-phase silica gel plate. PMID:15732898

  6. Merits of online electrochemistry liquid sample desorption electrospray ionization mass spectrometry (EC/LS DESI MS).

    PubMed

    Looi, Wen Donq; Brown, Blake; Chamand, Laura; Brajter-Toth, Anna

    2016-03-01

    A new online electrochemistry/liquid sample desorption electrospray ionization mass spectrometry (EC/LS DESI MS) system with a simple electrochemical thin-layer flow-through cell was developed and tested using N,N-dimethyl-p-phenylenediamine (DMPA) as a model probe. Although oxidation of DMPA is observed as a result of ionization of LS in positive ion mode LS DESI, application of voltage to the online electrochemical (EC) cell in EC/LS DESI MS increases yields of oxidation products. An advantage of LS DESI MS is its sensitivity in aqueous electrolyte solutions, which improves efficiency of electrochemical reactions in EC/LS DESI MS. In highly conductive low pH aqueous buffer solutions, oxidation efficiency is close to 100 %. EC/ESI MS typically requires mixed aqueous/organic solvents and low electrolyte concentrations for efficient ionization in MS, limiting efficiency of electrochemistry online with MS. Independently, the results verify higher electrochemical oxidation efficiency during positive mode ESI than during LS DESI. Graphical abstract Detection of DMPA oxidation in online electrochemical cell with EC/LS DESI MS. PMID:26886744

  7. Identification of organic pigments in automotive coatings using laser desorption mass spectrometry.

    PubMed

    Stachura, Sylwia; Desiderio, Vincent J; Allison, John

    2007-05-01

    When one looks at an automotive coating, one sees color due to pigments. Modern organic pigments, with high molar absorptivities, may be only minor components of the mixture. Laser desorption mass spectrometry (LDMS) has been shown to be a useful tool for the analysis of colorants such as pen ink dyes. Here, LDMS is used to determine its utility for the identification of pigments, in simple media and in more complex paints. Small paint chips can be introduced into the LDMS instrument, and when an ultraviolet laser is focused on a portion of a chip, ions representative of the pigment(s) are selectively formed. Some pigments such as quinacridones and copper phthalocyanine are very stable and are desorbed and ionized intact. In contrast, benzimidazolones, which contain some single-skeletal bonds, form fragment ions. This method proves to be sensitive and convenient, as no sample preparation is required. The presence of inorganic pigments in addition to modern organic pigments can be determined, and pigments can be directly identified in actual automotive paint chip samples. PMID:17456087

  8. Selective detection of homocysteine by laser desorption/ionization mass spectrometry.

    PubMed

    Su, Chih-Lin; Tseng, Wei-Lung

    2006-01-01

    This article describes the use of 2,3-naphthalenedicarboxaldehyde (NDA) as a selective probe for the determination of homocysteine (HCys) via fluorescence measurement and laser desorption/ionization mass spectrometry (LDI-MS). The derivatives of three aminothiols-HCys, glutathione (GSH), and gamma-glutamylcysteine (gamma-Glu-Cys)-with NDA under alkaline conditions possess different fluorescence emission characteristics, which allow us to identify them from amines, amino acids, and thiols. By selecting appropriate pH and excitation wavelengths, the limits of detection (LODs) at a signal-to-noise ratio of 3 were 5.2, 1.4 and 16 nM for HCys, GSH and gamma-Glu-Cys, respectively. Additionally, strong UV absorption of the NDA-HCys derivative was further observed at 331 nm; it could be directly detected by LDI-MS with a 337-nm nitrogen laser. Selective detection of HCys has been achieved by conducting the LDI-MS of the NDA-HCys derivative, which was found at m/z 406.9. The lowest detectable concentration of the NDA-HCys derivative in this approach was 500 nM. Quantitative determination of HCys in urine samples was accomplished by LDI-MS. Also, a calibration curve was created from plasma samples spiked with standard HCys (20-100 microM). The experimental results suggest that our proposed methods have great potential in clinical diagnosis and metabolomics application. PMID:17044125

  9. Identification of colorants in pigmented pen inks by laser desorption mass spectrometry.

    PubMed

    Papson, Kaitlin; Stachura, Sylwia; Boralsky, Luke; Allison, John

    2008-01-01

    Pigments are rapidly replacing dyes as colorants in pen and printer inks, due to their superior colors and stability. Unfortunately, tools commonly used in questioned document examination for analyzing pen inks, such as TLC, cannot be used for the analysis of insoluble pigments on paper. Laser desorption mass spectrometry is demonstrated here as a tool for analyzing pigment-based pen inks. A pulsed nitrogen laser can be focused onto a pen stroke from a pigmented ink pen on paper, and positive and negative ions representative of the pigment can be generated for subsequent mass spectrometric analysis. Targeted pens for this work were a set of Uni-ball 207 pigmented ink pens containing blue, light blue, orange, green, violet, red, pink, and black inks. Copper phthalocyanine was identified as the pigment used to make both blue inks. A mixture of halogenated copper phthalocyanines were identified in the green ink. Unexpectedly, the pink ink was found to contain a red pigment, Pigment Red 12, treated with a mixture of water-soluble dyes. Each sample yielded ions representative of the pigments present. PMID:18279246

  10. High-speed tandem mass spectrometric in situ imaging by nanospray desorption electrospray ionization mass spectrometry.

    PubMed

    Lanekoff, Ingela; Burnum-Johnson, Kristin; Thomas, Mathew; Short, Joshua; Carson, James P; Cha, Jeeyeon; Dey, Sudhansu K; Yang, Pengxiang; Prieto Conaway, Maria C; Laskin, Julia

    2013-10-15

    Nanospray desorption electrospray ionization (nano-DESI) combined with tandem mass spectrometry (MS/MS), high-resolution mass analysis of the fragment ions (m/Δm = 17 500 at m/z 200), and rapid spectral acquisition enabled simultaneous imaging and identification of a large number of metabolites and lipids from 92 selected m/z windows (±1 Da) with a spatial resolution of better than 150 μm. Mouse uterine sections of implantation sites on day 6 of pregnancy were analyzed in the ambient environment without any sample pretreatment. MS/MS imaging was performed by scanning the sample under the nano-DESI probe at 10 μm/s, while higher-energy collision-induced dissociation (HCD) spectra were acquired for a targeted inclusion list of 92 m/z values at a rate of ∼6.3 spectra/s. Molecular ions and their corresponding fragments, separated by high-resolution mass analysis, were assigned on the basis of accurate mass measurement. Using this approach, we were able to identify and image both abundant and low-abundance isobaric and isomeric species within each m/z window. MS/MS analysis enabled efficient separation and identification of isomeric and isobaric phospholipids that are difficult to separate in full-scan mode. Furthermore, we identified several metabolites associated with early pregnancy and obtained the first 2D images of these molecules. PMID:24040919

  11. Imaging Nicotine in Rat Brain Tissue by Use of Nanospray Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Lanekoff, Ingela T.; Thomas, Mathew; Carson, James P.; Smith, Jordan N.; Timchalk, Charles; Laskin, Julia

    2013-01-15

    Imaging mass spectrometry offers simultaneous detection of drugs, drug metabolites and endogenous substances in a single experiment. This is important when evaluating effects of a drug on a complex organ system such as the brain, where there is a need to understand how regional drug distribution impacts function. Nicotine is an addictive drug and its action in the brain is of high interest. Here we use nanospray desorption electrospray ionization, nano-DESI, imaging to discover the localization of nicotine in rat brain tissue after in vivo administration of nicotine. Nano-DESI is a new ambient technique that enables spatially-resolved analysis of tissue samples without special sample pretreatment. We demonstrate high sensitivity of nano-DESI imaging that enables detection of only 0.7 fmole nicotine per pixel in the complex brain matrix. Furthermore, by adding deuterated nicotine to the solvent, we examined how matrix effects, ion suppression, and normalization affect the observed nicotine distribution. Finally, we provide preliminary results suggesting that nicotine localizes to the hippocampal substructure called dentate gyrus.

  12. Distribution of terfenadine and its metabolites in locusts studied by desorption electrospray ionization mass spectrometry imaging.

    PubMed

    Olsen, Line Rørbæk; Hansen, Steen Honoré; Janfelt, Christian

    2015-03-01

    Desorption electrospray ionization (DESI) mass spectrometry (MS) imaging was used to image locusts dosed with the antihistamine drug terfenadine. The study was conducted in order to elucidate a relatively high elimination rate of terfenadine from the locust hemolymph. In this one of the few MS imaging studies on insects, a method for cryosectioning of whole locusts was developed, and the distributions of a number of endogenous compounds are reported, including betaine and a number of amino acids and phospholipids. Terfenadine was detected in the stomach region and the intestine walls, whereas three different metabolites-terfenadine acid (fexofenadine), terfenadine glucoside, and terfenadine phosphate-were detected in significantly smaller amounts and only in the unexcreted feces in the lower part of the intestine. The use of MS/MS imaging was necessary in order to detect the metabolites. With use of DESI-MS imaging, no colocalization of the drug and the metabolites was observed, suggesting a very rapid excretion of metabolites into the feces. Additional liquid chromatography-MS investigations were performed on hemolymph and feces and showed some abundance of terfenadine and the three metabolites, although at low levels, in both the hemolymph and the feces. PMID:25404166

  13. Direct detection of chloramphenicol in honey by neutral desorption-extractive electrospray ionization mass spectrometry.

    PubMed

    Huang, X Y; Fang, X W; Zhang, X; Dai, X M; Guo, X L; Chen, H W; Luo, L P

    2014-11-01

    Herein, we constructed a platform of neutral desorption-extractive electrospray ionization mass spectrometry (ND-EESI-MS) for direct and rapid detection of chloramphenicol (CAP) in honey samples diluted with methanol. Under the optimized working conditions, the quantitative information of CAP residues was acquired effectively by EESI-Ion Trap MS (n) . Using heated methanol-N2 as spray reagent, we reduced the limit of determination (LOD) from 73.3 ng/mL to 0.3 ng/mL, and the CAP detection is linear in the range of 1-5000 ng/mL (R = 0.9947). For the honey samples with CAP of 10, 100, and 1000 ng/mL, the recoveries were 133.0, 80.6, and 101.1%, and the relative standard deviations were 5.96, 8.82, and 8.71%, respectively. The reproducibility assays showed the stability of this method. Therefore, this ND-EESI-MS method is powerful for direct, rapid, and quantitative CAP analysis in honey samples with high sensitivity, precision, and specificity. PMID:25277102

  14. Chemical Analysis of Organic Aerosols Using Reactive Nanospray Desorption Electrospray Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Laskin, A.; Laskin, J.; Nizkorodov, S.

    2013-12-01

    Nanospray Desorption Electrospray Ionization (nano-DESI) technique integrated with high resolution mass spectrometry (HR-MS) enables molecular level analysis of organic aerosol (OA) samples. In nano-DESI, analyte is desorbed into a small volume solvent bridge formed between two capillaries positioned in contact with analyte and enables fast and efficient characterization of OA collected on substrates without sample preparation. We report applications of the nano-DESI/HR-MS approach in a number of our recent studies focused on molecular identification of organic compounds in laboratory and in field collected OA samples. Reactive nano-DESI approach where selected reagent is added to the solvent is used for examining the presence of individual species containing specific functional groups and for their quantification within complex mixtures of OA. Specifically, we use the Girard's reagent T (GT) to probe and quantify carbonyl compounds in the SOA mixtures. We estimate for the first time the amounts of dimers and trimers in the SOA mixtures. We found that the most abundant dimer in limonene/O3 SOA was detected at the ˜0.5 pg level and the total amount of dimers and trimers in the analyzed sample was ˜11 pg. Understanding of the OA composition at the molecular level allowed us to identify key aging reactions, including the transformation of carbonyls to imines and carbonyl-imine oligomerization, that may contribute to the formation of brown carbon in the atmosphere.

  15. Rapid detection of terbufos in stomach contents using desorption electrospray ionization mass spectrometry.

    PubMed

    Wilson, Christina R; Mulligan, Christopher C; Strueh, Kurt D; Stevenson, Gregory W; Hooser, Stephen B

    2014-03-26

    Desorption electrospray ionization mass spectrometry (DESI-MS) is an emerging analytical technique that permits the rapid and direct analysis of biological or environmental samples under ambient conditions. Highlighting the versatility of this technique, DESI-MS has been used for the rapid detection of illicit drugs, chemical warfare agents, agricultural chemicals, and pharmaceuticals from a variety of sample matrices. In diagnostic veterinary toxicology, analyzing samples using traditional analytical instrumentation typically includes extensive sample extraction procedures, which can be time consuming and labor intensive. Therefore, efforts to expedite sample analyses are a constant goal for diagnostic toxicology laboratories. In the current report, DESI-MS was used to directly analyze stomach contents from a dog exposed to the organophosphate insecticide terbufos. The total DESI-MS analysis time required to confirm the presence of terbufos and diagnose organophosphate poisoning in this case was approximately 5 min. This highlights the potential of this analytical technique in the field of veterinary toxicology for the rapid diagnosis and detection of toxicants in biological samples. PMID:24670950

  16. Metabolic profiling directly from the Petri dish using nanospray desorption electrospray ionization imaging mass spectrometry.

    PubMed

    Watrous, Jeramie; Roach, Patrick; Heath, Brandi; Alexandrov, Theodore; Laskin, Julia; Dorrestein, Pieter C

    2013-11-01

    Understanding molecular interaction pathways in complex biological systems constitutes a treasure trove of knowledge that might facilitate the specific, chemical manipulation of the countless microbiological systems that occur throughout our world. However, there is a lack of methodologies that allow the direct investigation of chemical gradients and interactions in living biological systems, in real time. Here, we report the use of nanospray desorption electrospray ionization (nanoDESI) imaging mass spectrometry for in vivo metabolic profiling of living bacterial colonies directly from the Petri dish with absolutely no sample preparation needed. Using this technique, we investigated single colonies of Shewanella oneidensis MR-1, Bacillus subtilis 3610, and Streptomyces coelicolor A3(2) as well as a mixed biofilm of S. oneidensis MR-1 and B. subtilis 3610. Data from B. subtilis 3610 and S. coelicolor A3(2) provided a means of validation for the method while data from S. oneidensis MR-1 and the mixed biofilm showed a wide range of compounds that this bacterium uses for the dissimilatory reduction of extracellular metal oxides, including riboflavin, iron-bound heme and heme biosynthetic intermediates, and the siderophore putrebactin. PMID:24047514

  17. Beer fingerprinting by Matrix-Assisted Laser Desorption-Ionisation-Time of Flight Mass Spectrometry.

    PubMed

    Šedo, Ondrej; Márová, Ivana; Zdráhal, Zbyněk

    2012-11-15

    A method allowing parallel fingerprinting of proteins and maltooligosaccharides directly from untreated beer samples is presented. These two classes of compounds were detected by Matrix-Assisted Laser Desorption-Ionisation-Time of Flight-Mass Spectrometry (MALDI-TOF-MS) analysis of beer mixed with 2,5-dihydroxybenzoic acid solution. The maltooligosaccharide profiles acquired from the MALDI sample spot center were not found characteristic for beers of different source and technology. On the other hand, according to profiles containing protein signals acquired from crystals formed on the border of the MALDI sample spot, we were able to distinguish beer samples of the same brand produced by different breweries. The discriminatory abilities of the method were further examined on a set of 17 lager beers, where the fingerprints containing protein signals enabled resolution of majority of examined brands. We propose MALDI-TOF-MS profiling as a rapid tool for beer brewing technology process monitoring, quality control, and determination of beer authenticity. PMID:22868116

  18. Analysis of mainstream and sidestream cigarette smoke particulate matter by laser desorption mass spectrometry.

    PubMed

    Schramm, Sébastien; Carré, Vincent; Scheffler, Jean-Luc; Aubriet, Frédéric

    2011-01-01

    Laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (LDI-FTICRMS) was used to investigate particulate matter (PM) associated with mainstream (MSS) and sidestream cigarette smokes (SSS). The high mass resolution and the high mass measurement accuracy allowed a molecular formula for each detected signal in the 150-500 m/z range to be assigned. The high number of peaks observed in mass spectra required additional data processing to extract information. In this context, Kendrick maps and Van Krevelen diagrams were drawn. These postacquisition treatments were used to more easily compare different cigarette smokes: (i) MSS from different cigarettes and (ii) MSS and SSS from the same cigarette. In both ion detection modes, most of the detected species were found to be attributed to C(6-31)H(2-35)N(0-7)O(0-9) compounds. The compounds observed in the study of SSS appeared to be more unsaturated and less oxygenated than those observed when MSS of the same cigarette was investigated. PMID:21126024

  19. Matrix assisted laser desorption ionization mass spectrometry imaging identifies markers of ageing and osteoarthritic cartilage

    PubMed Central

    2014-01-01

    Introduction Cartilage protein distribution and the changes that occur in cartilage ageing and disease are essential in understanding the process of cartilage ageing and age related diseases such as osteoarthritis. The aim of this study was to investigate the peptide profiles in ageing and osteoarthritic (OA) cartilage sections using matrix assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI). Methods The distribution of proteins in young, old and OA equine cartilage was compared following tryptic digestion of cartilage slices and MALDI-MSI undertaken with a MALDI SYNAPT™ HDMS system. Protein identification was undertaken using database searches following multivariate analysis. Peptide intensity differences between young, ageing and OA cartilage were imaged with Biomap software. Analysis of aggrecanase specific cleavage patterns of a crude cartilage proteoglycan extract were used to validate some of the differences in peptide intensity identified. Immunohistochemistry studies validated the differences in protein abundance. Results Young, old and OA equine cartilage was discriminated based on their peptide signature using discriminant analysis. Proteins including aggrecan core protein, fibromodulin, and cartilage oligomeric matrix protein were identified and localised. Fibronectin peptides displayed a stronger intensity in OA cartilage. Age-specific protein markers for collectin-43 and cartilage oligomeric matrix protein were identified. In addition potential fibromodulin and biglycan peptides targeted for degradation in OA were detected. Conclusions MALDI-MSI provided a novel platform to study cartilage ageing and disease enabling age and disease specific peptides in cartilage to be elucidated and spatially resolved. PMID:24886698

  20. High-Speed Tandem Mass Spectrometric in Situ Imaging by Nanospray Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Lanekoff, Ingela T.; Burnum-Johnson, Kristin E.; Thomas, Mathew; Short, Joshua TL; Carson, James P.; Cha, Jeeyeon; Dey, Sudhansu K.; Yang, Pengxiang; Prieto Conaway, Maria C.; Laskin, Julia

    2013-10-15

    Nanospray desorption electrospray ionization (nano-DESI) combined with tandem mass spectrometry (MS/MS), high-resolution mass analysis (m/m=17,500 at m/z 200), and rapid spectral acquisition enabled simultaneous imaging and identification of more than 300 molecules from 92 selected m/z windows (± 1 Da) with a spatial resolution of better than 150 um. Uterine sections of implantation sites on day 6 of pregnancy were analyzed in the ambient environment without any sample pre-treatment. MS/MS imaging was performed by scanning the sample under the nano-DESI probe at 10 um/s while acquiring higher-energy collision-induced dissociation (HCD) spectra for a targeted inclusion list of 92 m/z values at a rate of ~6.3 spectra/s. Molecular ions and their corresponding fragments, separated using high-resolution mass analysis, were assigned based on accurate mass measurement. Using this approach, we were able to identify and image both abundant and low-abundance isobaric species within each m/z window. MS/MS analysis enabled efficient separation and identification of isobaric sodium and potassium adducts of phospholipids. Furthermore, we identified several metabolites associated with early pregnancy and obtained the first 2D images of these molecules.

  1. Towards monitoring of protein purification by matrix-assisted laser desorption ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Jensen, Charlotte; Haebel, Sophie; Andersen, Svend Olav; Roepstorff, Peter

    1997-01-01

    The purpose of the present study is to investigate if Matrix-Assisted Laser Desorption Ionization (MALDI) Mass Spectrometry (MS) can be used as a general method for monitoring protein purification procedures. With this aim, the compatibility of MALDI/MS with protein samples containing various buffers, salts and detergents commonly used in protein purification is examined. The pH value of the sample during the crystallization process is found to be the critical point. As long as the pH value is kept below 2 by the addition of sufficiently concentrated trifluoroacetic acid (TFA), spectra can be obtained from solutions containing high concentrations of buffer or salts and up to 0.2% of sodium dodecyl sulfate (SDS). Reference spectra can be obtained by MALDI/MS of proteins electroeluted from electrophoretic gels as demonstrated using 2D-PAGE and further specificity obtained by preparing mass spectrometric peptide maps from the eluate. The value of the concept is demonstrated by relating the proteins purified from an extract of meal worm cuticle proteins with 2D-PAGE of the total extract. Finally a general strategy for monitoring protein purification by MALDI/MS is outlined and discussed.

  2. The Effect of Culture Conditions on Microorganism Identification by Matrix-Assisted Laser Desorption Ionization Mass Spectrometry

    SciTech Connect

    Valentine, Nancy B.; Wunschel, Sharon C.; Wunschel, David S.; Petersen, Catherine E.; Wahl, Karen L.

    2005-01-01

    Abstract Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been used to identify bacteria based upon protein signatures. This research shows that while some different proteins are produced by vegetative bacteria when they are cultured in different growth media, positive identification with MALDI-TOF MS is still possible with the protocol established at Pacific Northwest National Laboratory (PNNL)(11). A core set of small proteins remain constant under at least four different culture media conditions including minimal medium -M9, rich media - tryptic soy broth (TSB) or Luria-Bertani (LB) broth and blood agar plates such that analysis of the intact cells by matrix-assisted laser desorption/ionization mass spectrometry allows for consistent identification.

  3. Flash desorption/mass spectrometry for the analysis of less- and nonvolatile samples using a linearly driven heated metal filament.

    PubMed

    Usmanov, Dilshadbek T; Ninomiya, Satoshi; Hiraoka, Kenzo

    2013-11-01

    In this paper, the important issue of the desorption of less- and nonvolatile compounds with minimal sample decomposition in ambient mass spectrometry is approached using ambient flash desorption mass spectrometry. The preheated stainless steel filament was driven down and up along the vertical axis in 0.3 s. At the lowest position, it touched the surface of the sample with an invasion depth of 0.1 mm in 50 ms (flash heating) and was removed from the surface (fast cooling). The heating rate corresponds to ~10(4) °C/s at the filament temperature of 500 °C. The desorbed gaseous molecules were ionized by using a dielectric barrier discharge ion source, and the produced ions were detected by a time-of-flight (TOF) mass spectrometer. Less-volatile samples, such as pharmaceutical tablets, narcotics, explosives, and C60 gave molecular and protonated molecule ions as major ions with thermal decomposition minimally suppressed. For synthetic polymers (PMMA, PLA, and PS), the mass spectra reflected their backbone structures because of the suppression of the sequential thermal decompositions of the primary products. The present technique appears to be suitable for high-throughput qualitative analyses of many types of solid samples in the range from a few ng to 10 μg with minimal sample consumption. Some contribution from tribodesorption in addition to thermal desorption was suggested for the desorption processes. Figure ᅟ PMID:23982934

  4. Flash Desorption/Mass Spectrometry for the Analysis of Less- and Nonvolatile Samples Using a Linearly Driven Heated Metal Filament

    NASA Astrophysics Data System (ADS)

    Usmanov, Dilshadbek T.; Ninomiya, Satoshi; Hiraoka, Kenzo

    2013-11-01

    In this paper, the important issue of the desorption of less- and nonvolatile compounds with minimal sample decomposition in ambient mass spectrometry is approached using ambient flash desorption mass spectrometry. The preheated stainless steel filament was driven down and up along the vertical axis in 0.3 s. At the lowest position, it touched the surface of the sample with an invasion depth of 0.1 mm in 50 ms (flash heating) and was removed from the surface (fast cooling). The heating rate corresponds to ~104 °C/s at the filament temperature of 500 °C. The desorbed gaseous molecules were ionized by using a dielectric barrier discharge ion source, and the produced ions were detected by a time-of-flight (TOF) mass spectrometer. Less-volatile samples, such as pharmaceutical tablets, narcotics, explosives, and C60 gave molecular and protonated molecule ions as major ions with thermal decomposition minimally suppressed. For synthetic polymers (PMMA, PLA, and PS), the mass spectra reflected their backbone structures because of the suppression of the sequential thermal decompositions of the primary products. The present technique appears to be suitable for high-throughput qualitative analyses of many types of solid samples in the range from a few ng to 10 μg with minimal sample consumption. Some contribution from tribodesorption in addition to thermal desorption was suggested for the desorption processes. [Figure not available: see fulltext.

  5. Rapid Detection of OXA-48-Producing Enterobacteriaceae by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry.

    PubMed

    Oviaño, Marina; Barba, Maria José; Fernández, Begoña; Ortega, Adriana; Aracil, Belén; Oteo, Jesús; Campos, José; Bou, Germán

    2016-03-01

    A rapid and sensitive (100%) matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) assay was developed to detect OXA-48-type producers, using 161 previously characterized clinical isolates. Ertapenem was monitored to detect carbapenem resistance, and temocillin was included in the assay as a marker for OXA-48-producers. Structural analysis of temocillin is described. Data are obtained within 60 min. PMID:26677247

  6. Gold nanoparticles assisted laser desorption/ionization mass spectrometry and applications: from simple molecules to intact cells.

    PubMed

    Abdelhamid, Hani Nasser; Wu, Hui-Fen

    2016-07-01

    Gold nanoparticles (AuNPs) assisted laser desorption/ionization mass spectrometry (GALDI-MS) provided new horizons and offered many functions for various applications. This review summarized AuNPs applications for analytical, biotechnology and proteomics. AuNPs efficiently absorbed the laser radiation and transferred the energy to the analyte for the desorption/ionization process. The unique features of AuNPs such as large surface area and high absorption coefficient lead not only to high resolution, low interference and low limit of detection, but also offered selective detection for certain species. AuNPs provided an excellent surface for the analysis of several species such as small molecules, biomarkers, proteins and cells (pathogenic bacteria or cancer cells). AuNPs played many roles such as surface for LDI-MS, probe and stationary phase for separation or preconcentration. AuNPs modified various surface chemistry was applied for a wide range of different wavelength. AuNPs severed as a source of Au(+) ions that were suitable for analyte cationisation. Characterization of Au nanoclusters (AuNCs) by mass spectrometry, pros and cons were also highlighted. Graphical Abstract Schematic representation of the analysis by Gold Nanoparticles Assisted Laser Desorption/Ionization Mass Spectrometry (GALDI-MS). PMID:26973236

  7. Jarosite as a Storage Mineral for Small Organic Molecules: Investigations of Natural Samples Using an 'In Situ' Laser Desorption Fourier Transform Mass Spectrometry Technique

    NASA Astrophysics Data System (ADS)

    Kotler, J. M.; Hinman, N. W.; Yan, B.; Stoner, D. L.; Scott, J. R.

    2007-03-01

    The use of laser desorption Fourier transform mass spectrometry has revealed the presence of organic matter in several jarosite samples from various locations worldwide including jarosite precipitated in the lab by acidothiobacillus ferroxidans.

  8. Isomeric differentiation of polycyclic aromatic hydrocarbons using silver nitrate reactive desorption electrospray ionization mass spectrometry

    PubMed Central

    Eftekhari, Mohammad; Ismail, Ali I.; Zare, Richard N.

    2014-01-01

    RATIONALE Polycyclic aromatic hydrocarbons (PAHs) are nonpolar and difficult to detect by desorption electrospray ionization. We present a new detection method based on cationization with silver ions, which has the added advantage of being able to differentiate PAHs with the same mass but different structure. METHODS 9,10-Diphenylanthracene and triptycene, in addition to four different groups of PAH isomers: (1) anthracene and phenanthrene, (2) pyrene and fluoranthene, (3) benz[a]anthracene, benz[b]anthracene (tetracene), and chrysene (4) benzo[a]pyrene and benzo[k]fluoranthene, were deposited on a paper surface and bombarded with methanol droplets containing silver nitrate. The resulting microdroplets entered a quadruple mass spectrometer for mass analysis. RESULTS The mass spectrum shows [PAH]+, [Ag + OH + PAH]+, and [Ag(PAH)n]+ n (n = 1, 2) (and [PAH + O2]+ in the case of benz[b]anthracene) ions. PAHs having a bay structure, such as phenanthrene, showed a different tendency to interact with silver ions from those PAHs having a linear arrangement of the fused benzene rings, such as anthracene. The ratios of the [PAH]+ peak intensity to that of [Ag–PAH]+, [Ag + OH + PAH]+, [Ag(PAH)2]+, and [PAH + O2]+ were used to differentiate the PAH isomers sharing the same molecular formula with different structures. For isomeric mixtures the [PAH]+ to [Ag + OH + PAH]+ ratio was found to be the most useful parameter. The uncertainty in the mole fraction of an isomeric mixture was ±0.09, 0.13, ±0.25, and ±0.1 for phenanthrene-anthracene, fl benz[a] anthracene-chrysene, and benzo[a]pyrene-benzo[k]fluoranthene, respectively. CONCLUSIONS A simple method has been developed for the detection of PAHs in desorption electrospray ionization mass spectrometry based on Ag(I) cationization. The method showed a capability to differentiate PAHs isomers (having the same molecular mass) in isomeric mixture with an uncertainty in the mole fraction of about 0.1. At high inlet temperature

  9. Matrix-assisted laser-desorption-ionization mass spectrometry of proteins using a free-electron laser

    SciTech Connect

    Cramer, R.; Hillenkamp, F.; Haglund, R.

    1995-12-31

    Matrix-assisted laser desorption-ionization (MALDI) mass spectrometry (MS) is one of the most promising techniques for spectral fingerprinting large molecules, such as proteins, oligonucleotides and carbohydrates. In the usual implementation of this technique, the analyte molecule is dissolved in an aromatic liquid matrix material which resonantly absorbs ultraviolet laser light. Resonant absorption by {pi}-{pi}* transitions volatilizes the matrix and initiates subsequent charge transfer to the analyte molecules, which are detected by time-of-flight mass spectrometry. Recent MALDI-MS studies with Er:YAG (2.94 {mu}m) and CO{sub 2}{sup 4} (9.4-10.6 {mu}m) lasers suggest that them is significant unexplored potential for mass spectrometry of macromolecules, including oligonucleotide, in the mid-infrared. Preliminary experiments show that it is possible to capitalize on the rich rovibronic absorption spectrum of virtually all organics to initiate resonant desorption in matrix material over the entire range of pH values. However, the mechanism of charge transfer is particularly problematic for infrared MALDI because of the low photon energy. In this paper, we report the results of MALI-MS studies on small proteins using the Vanderbilt FEL and several matrix materials. Proteins with masses up to roughly 6,000 amu were detected with high resolution in a linear time-of-flight mass spectrometer. By varying the pulse duration using a broadband Pockels cell, we have been able to compare the results of relatively long (5 {mu}s) and short (0.1 {mu}s) irradiation on the desorption and ionization processes. Compared to uv-MALDI spectra of identical analytes obtained with a nitrogen laser (337 nm) in the same time-of-flight spectrometer, the infrared results appear to show that the desorption and ionization process goes on over a somewhat longer time scale.

  10. Nitrogen Molecule Adsorption on Cationic Tantalum Clusters and Rhodium Clusters and Desorption from Their Nitride Clusters Studied by Thermal Desorption Spectrometry.

    PubMed

    Mafuné, Fumitaka; Tawaraya, Yuki; Kudoh, Satoshi

    2016-06-23

    Adsorption and desorption of N2 molecules onto cationic Ta and Rh clusters in the gas phase were investigated in the temperature range of 300-1000 K by using thermal desorption spectrometry in combination with density functional theory (DFT) calculations. For Ta6(+), the first N2 molecule was found to adsorb dissociatively, and it remained adsorbed when Ta6(+)N2 was heated to 1000 K. In contrast, the second and the subsequent N2 molecules adsorbed weakly as a molecular form and were released into the gas phase when heated to 600 K. The difference can be explained in terms of the activation barrier between the molecular and dissociative forms. On the other hand, when Ta clusters were generated in the presence of N2 gas by the laser ablation of a Ta rod, isomeric clusters, TanNm(+), having heat resistivity were formed. For Rh6(+), N2 adsorbed molecularly at 300 K and desorbed totally at 450 K. These results were consistent with the DFT calculations, indicating that the dissociative adsorption of N2 is endothermic. PMID:27276438

  11. The dissociation kinetics of NO on Rh(111) as studied by temperature programmed static secondary ion mass spectrometry and desorption

    NASA Astrophysics Data System (ADS)

    Borg, H. J.; Reijerse, J. F. C.-J. M.; van Santen, R. A.; Niemantsverdriet, J. W.

    1994-12-01

    Temperature programmed static secondary ion mass spectrometry (TPSSIMS) and temperature programmed desorption (TPD) have been used to study the kinetics of adsorption, dissociation, and desorption of NO on Rh(111). At 100 K, NO adsorption is molecular and proceeds via mobile precursor state kinetics with a high initial sticking probability. SSIMS indicates the presence of two distinct NO adsorption states, indicative of threefold adsorption at low coverage, and occupation of bridge sites at higher coverages. Three characteristic coverage regimes appear with respect to NO dissociation. At low coverages θNO<0.25 ML, NO dissociates completely at temperatures between 275 and 340 K. If we neglect lateral interactions and assume pure first order dissociation kinetics, we find effective values for the activation barrier and preexponential factor of 40±6 kJ/mol and 106±1 s-1 for the dissociation of 0.15-0.20 ML NO. However, if we assume that a NO molecule needs an ensemble of three to four vacant sites in order to dissociate, the preexponential factor and activation energy are ˜1011 s-1 and 65 kJ/mol, in better agreement with transition state theory expectations. The Nads and Oads dissociation products desorb as N2 and O2, respectively, with desorption parameters Edes=118±10 kJ/mol and νdes=1010.1±1.0 s-1 for N2 in the zero coverage limit. At higher coverages, the desorption kinetics of N2 is strongly influenced by the presence of coadsorbed oxygen. In the medium coverage range 0.25<θNO<0.50 ML, part of the NO desorbs molecularly, with an estimated desorption barrier of 113±10 kJ/mol and a preexponential of 1013.5±1.0 s-1. Dissociation of NO becomes progressively inhibited due to site blocking, the onset shifting from 275 K at 0.25 ML to 400 K, coinciding with the NO desorption temperature, at a coverage of 0.50 ML. The accumulation of nitrogen and oxygen atoms on the highly covered surface causes a destabilization of the nitrogen atoms, which results in an

  12. Chemical Analysis of Complex Organic Mixtures Using Reactive Nanospray Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Laskin, Julia; Eckert, Peter A.; Roach, Patrick J.; Heath, Brandi S.; Nizkorodov, Sergey A.; Laskin, Alexander

    2012-08-21

    Reactive nanospray desorption electrospray ionization (nano-DESI) combined with high-resolution mass spectrometry was utilized for the analysis of secondary organic aerosol produced through ozonolysis of limonene (LSOA). Previous studies showed that LSOA constituents are multifunctional compounds containing aldehyde and ketone groups. In this study, we used the selectivity of the Girard T (GT) reagent towards carbonyl compounds to examine the utility of reactive nano-DESI for the analysis of complex organic mixtures. In these experiments, 1-100 {micro}M GT solution was used as a working solvent for reactive nano-DESI analysis. Abundant products of a single addition of GT to LSOA constituents were observed at GT concentrations in excess of 10 {micro}M. We found that LSOA compounds with 18-20 carbon atoms (dimers) and 27-30 carbon atoms (trimers) react with GT through a simple addition reaction resulting in formation of the carbinolamine derivative. In contrast, reactions of GT with monomeric species result in formation of both the carbinolamine and the hydrazone derivatives. In addition, several monomers did not react with GT on the timescale of our experiment. These molecules were characterized by relatively high values of the double bond equivalent (DBE) and low oxygen content. Furthermore, because addition of a charged GT tag to a neutral molecule eliminates the discrimination against the low proton affinity compounds in the ionization process, reactive nano-DESI analysis enables quantification of individual compounds in the complex mixture. For example, we were able to estimate for the first time the amounts of dimers and trimers in the LSOA mixture. Specifically, we found that the most abundant LSOA dimer was detected at ca. 0.5 pg level and the total amount of dimers and trimers in the analyzed sample was just around 11 pg. Our results indicate that reactive nano-DESI is a valuable approach for examining the presence of specific functional groups and

  13. Trapping state of hydrogen isotopes in carbon and graphite investigated by thermal desorption spectrometry

    SciTech Connect

    Atsumi, H.; Tanabe, T.; Shikama, T.

    2015-03-15

    Thermal desorption spectrometry (TDS) has been investigated to obtain fundamental information of tritium behavior in graphite and carbon materials especially at high temperatures. 29 brands of graphite, HOPG, glassy carbon and CFC materials charged with deuterium gas are tested up to the temperature of 1735 K with a heating rate of 0.1 K/s. TDS spectra have five peaks at 600-700 K, around 900 K, 1200 K, 1300-1450 K and 1600-1650 K. The amounts of released deuterium have been compared with crystallographic parameters derived from XRD analysis. The results can be summarized as follows. First, TDS spectra of deuterium were quite varied among the samples tested, such as existence of peaks, peak temperatures and release amounts of deuterium. Secondly, TDS spectra may consist of five peaks, which are peak 1 (600-700 K), peak 2 (around 900 K), peak 3 (around 1200 K), peak 4 (1300-1450 K) and peak 5 (1600-1650 K). Thirdly, the correlations between the estimated surface area of edge surface and the total amount of released deuterium could be observed for peaks 4 and 5. Fourthly, high energy trapping site (peak 5) may exist even at edge surface or a near surface region, not only for intercalary. And fifth, in order to obtain the lower tritium retention for graphite and CFC materials, the material should be composed of a filler grain with a smaller crystallite size or having the smaller net edge surface in its structure. It is shown that heat treatment does not reduce originally existing trapping sites but trapping sites generated by neutron irradiation for instance can be reduced in some degree.

  14. Characterization of the Cathode Electrolyte Interface in Lithium Ion Batteries by Desorption Electrospray Ionization Mass Spectrometry.

    PubMed

    Liu, Yao-Min; G Nicolau, Bruno; Esbenshade, Jennifer L; Gewirth, Andrew A

    2016-07-19

    The solid electrolyte interface (SEI) formed via electrolyte decomposition on the anode of lithium ion batteries is largely responsible for the stable cycling of conventional lithium ion batteries. Similarly, there is a lesser-known analogous layer on the cathode side of a lithium ion battery, termed the cathode electrolyte interface (CEI), whose composition and role are debated. To confirm the existence and composition of the CEI, desorption electrospray ionization mass spectrometry (DESI-MS) is applied to study common lithium ion battery cathodes. We observe CEI formation on the LiMn2O4 cathode material after cycling between 3.5 and 4.5 V vs Li/Li(+) in electrolyte solution containing 1 M LiPF6 or LiClO4 in 1:1 (v/v) ethylene carbonate (EC) and dimethyl carbonate (DMC). Intact poly(ethylene glycol) dimethyl ether is identified as the electrolyte degradation product on the cathode surface by the high mass-resolution Orbitrap mass spectrometer. When EC is paired with ethyl methyl carbonate (EMC), poly(ethylene glycol) dimethyl ether, poly(ethylene glycol) ethyl methyl ether, and poly(ethylene glycol) are found on the surface simultaneously. The presence of ethoxy and methoxy end groups indicates both methoxide and ethoxide are produced and involved in the process of oligomerization. Au surfaces cycled under different electrochemical windows as model systems for Li-ion battery anodes are also examined. Interestingly, the identical oligomeric species to those found in the CEI are found on Au surfaces after running five cycles between 2.0 and 0.1 V vs Li/Li(+) in half-cells. These results show that DESI-MS provides intact molecular information on battery electrodes, enabling deeper understanding of the SEI or CEI composition. PMID:27346184

  15. High-throughput proteomics using matrix-assisted laser desorption/ ionization mass spectrometry.

    PubMed

    Cramer, Rainer; Gobom, Johan; Nordhoff, Eckhard

    2005-06-01

    It has become evident that the mystery of life will not be deciphered just by decoding its blueprint, the genetic code. In the life and biomedical sciences, research efforts are now shifting from pure gene analysis to the analysis of all biomolecules involved in the machinery of life. One area of these postgenomic research fields is proteomics. Although proteomics, which basically encompasses the analysis of proteins, is not a new concept, it is far from being a research field that can rely on routine and large-scale analyses. At the time the term proteomics was coined, a gold-rush mentality was created, promising vast and quick riches (i.e., solutions to the immensely complex questions of life and disease). Predictably, the reality has been quite different. The complexity of proteomes and the wide variations in the abundances and chemical properties of their constituents has rendered the use of systematic analytical approaches only partially successful, and biologically meaningful results have been slow to arrive. However, to learn more about how cells and, hence, life works, it is essential to understand the proteins and their complex interactions in their native environment. This is why proteomics will be an important part of the biomedical sciences for the foreseeable future. Therefore, any advances in providing the tools that make protein analysis a more routine and large-scale business, ideally using automated and rapid analytical procedures, are highly sought after. This review will provide some basics, thoughts and ideas on the exploitation of matrix-assisted laser desorption/ ionization in biological mass spectrometry - one of the most commonly used analytical tools in proteomics - for high-throughput analyses. PMID:16000086

  16. Age determination of ballpoint pen ink by thermal desorption and gas chromatography-mass spectrometry.

    PubMed

    Bügler, Jürgen H; Buchner, Hans; Dallmayer, Anton

    2008-07-01

    Two main approaches can be used for determining the age of an ink: indirect dating and direct dating. Indirect dating is based on the chemical analysis of an ink followed by comparison with known samples in a reference collection. The collection should contain information about the inks including the market introduction dates. This approach may allow for an anachronism to be detected. The second concept is based on measuring ink components that change with age. The analysis of solvents in ballpoint inks may be a useful parameter for determining the age of ink on paper. In a previous study, the authors demonstrated that thermal desorption of ink directly from paper, followed by chemical analysis using gas chromatography-mass spectrometry (GC-MS), is a promising procedure for characterizing ink-binder resins and solvents. Preliminary tests showed that monitoring the evaporation of ink solvent from ink on paper is not a suitable method for ink dating. Thermal analysis of ink on paper in two steps revealed that fresh ink releases a relative amount of solvent at a certain low temperature in a defined period of time, which decreases as the ink ages. As a consequence, this relative amount of solvent released at a certain low temperature, and its decrease with time, can be used to estimate ink age. This age-dependent parameter was studied in 85 different inks ranging in age from 1 week to 1.5 years. It was found that some inks showed a significant decrease of this parameter up to an age of several months, and that the aging process can be monitored within this period. For other inks, however, the age-dependent parameter decreases relatively fast, e.g., within a few days, to a constant level, which can be too fast for casework. Based on these results, a general procedure for assessing the age of ballpoint pen inks on paper was developed. PMID:18503526

  17. Qualitative analysis of seized cocaine samples using desorption electrospray ionization- mass spectrometry (DESI-MS).

    PubMed

    Stojanovska, Natasha; Tahtouh, Mark; Kelly, Tamsin; Beavis, Alison; Fu, Shanlin

    2015-05-01

    Desorption electrospray ionization - mass spectrometry (DESI-MS) is a useful technique for the qualitative analysis of compounds found in seized drug material. In this study, DESI-MS was utilized in the screening analysis of illicit cocaine samples. The technique was also applied to the geographical origin determination of these samples. The limit of detection was determined to be 24.3 µg (or 3.47 µg/mm(2) ) and the analysis time was less than 1 minute per sample. The intra-day and inter-day precision for the detection of cocaine was 11 % and 42 %, respectively; therefore the quantitative data provided by DESI-MS was limited in its use for accurate determination of cocaine concentration in a sample. Using the quadrupole time-of-flight (QTOF) mass spectrometer, the presence of cocaine and impurities detected were confirmed by accurate tandem MS data. The qualitative chemical profiles obtained using DESI-MS were compared to two popular analysis techniques, GC-MS and LC-MS. The effects of a range of adulterants including caffeine, procaine, levamisole, lignocaine, paracetamol, and atropine on the detectability of cocaine were also investigated. It was found that the addition of these adulterants in a cocaine sample did not prevent the detection of the analyte itself (there was slight enhancement in some samples), which was useful in drug detection. The detection of truxillines in the seized samples by DESI-MS aided in the preliminary determination of geographical origin, i.e., Bolivian, Peruvian or Colombian leaf origin. The application of DESI-MS to the qualitative analysis and screening of seized cocaine samples demonstrates the potential and applicability of the technique to the fast chemical profiling of illicit samples. PMID:24943809

  18. Atmospheric pressure glow discharge desorption mass spectrometry for rapid screening of pesticides in food.

    PubMed

    Jecklin, Matthias Conradin; Gamez, Gerardo; Touboul, David; Zenobi, Renato

    2008-09-01

    Flowing afterglow atmospheric pressure glow discharge tandem mass spectrometry (APGD-MS/MS) is used for the analysis of trace amounts of pesticides in fruit juices and on fruit peel. The APGD source was rebuilt after Andrade et al. (Andrade et al., Anal. Chem. 2008; 80: 2646-2653; 2654-2663) and mounted onto a hybrid quadrupole time-of-flight mass spectrometer. Apple, cranberry, grape and orange juices as well as fruit peel and salad leaves were spiked with aqueous solutions containing trace amounts of the pesticides alachlor, atrazine, carbendazim, carbofuran, dinoseb, isoproturon, metolachlor, metolcarb, propoxur and simazine. Best limits of determination (LODs) of pesticides in the fruit juices were achieved for metolcarb (1 microg/L in apple juice), carbofuran and dinoseb (2 microg/L in apple juice); for the analysis of apple skin best LODs were 10 pg/cm(2) of atrazine, metolcarb and propoxur which corresponds to an estimated concentration of 0.01 microg/kg apple, taking into account the surface area and the weight of the apple. The measured LODs were within or below the allowed maximum residue levels (MRLs) decreed by the European Union (1-500 microg/kg for pesticides in fruit juice and 0.01-5 microg/kg for apple skin). No sample pretreatment (extraction, pre-concentration, chromatographic separation) was necessary to analyze these pesticides by direct desorption/ionization using APGD-MS and to identify them using MS/MS. This makes APGD-MS a powerful high-throughput tool for the investigation of very low amounts of pesticides in fruit juices and on fruit peel/vegetable skin. PMID:18697232

  19. Triple sorbent thermal desorption/gas chromatography/mass spectrometry determination of vapor phase organic contaminants

    SciTech Connect

    Ma, C.Y.; Skeen, J.T.; Dindal, A.B.; Higgins, C.E.; Jenkins, R.A.

    1994-05-01

    A thermal desorption/ps chromatography/mass spectrometry (TD/GC/MS) has been evaluated for the determination of volatile organic compounds (VOCS) in vapor phase samples using Carbosieve S-III/Carbotrap/Carotrap C triple sorbent traps (TST) similar to those available from a commercial source. The analysis was carried out with a Hewlett-Packard 5985A or 5995 GC/MS system with a modified injector to adapt an inhouse manufactured short-path desorber for transferring desorbate directly onto a cryofocusing loop for subsequent GC/MS analysis. Vapor phase standards generated from twenty six compounds were used for method validation, including alkanes, alkyl alcohols, alkyl ketones, and alkyl nitrites, a group of representative compounds that have previously been identified in a target airborne matrix. The method was validated based on the satisfactory results in terms of reproducibility, recovery rate, stability, and linearity. A relative, standard deviation of 0.55 to 24.3 % was obtained for the entire TD process (generation of gas phase standards, spiking the standards on and desorbing from TST) over a concentration range of 20 to 500 ng/trap. Linear correlation coefficients for the calibration curves as determined ranged from 0.81 to 0.99 and limits of detection ranged from 3 to 76 ng. For a majority of standards, recoveries of greater than 90% were observed. For three selected standards spiked on TSTS, minimal loss (10 to 22%) was observed after storing the spiked in, a 4{degree}C refrigerator for 29 days. The only chromatographable artifact observed was a 5% conversion of isopropanol to acetone. The validated method been successfully applied, to the determination of VOCs collected from various emission sources in a diversified concentration range.

  20. Chemical analysis of complex organic mixtures using reactive nanospray desorption electrospray ionization mass spectrometry.

    PubMed

    Laskin, Julia; Eckert, Peter A; Roach, Patrick J; Heath, Brandi S; Nizkorodov, Sergey A; Laskin, Alexander

    2012-08-21

    Reactive nanospray desorption electrospray ionization (nano-DESI) combined with high-resolution mass spectrometry was utilized for the analysis of secondary organic aerosol produced through ozonolysis of limonene (LSOA). Previous studies have shown that LSOA constituents are multifunctional compounds containing at least one aldehyde or ketone groups. In this study, we used the selectivity of the Girard's reagent T (GT) toward carbonyl compounds to examine the utility of reactive nano-DESI for the analysis of complex organic mixtures. In these experiments, 1-100 μM GT solutions were used as the working solvents for reactive nano-DESI analysis. Abundant products from the single addition of GT to LSOA constituents were observed at GT concentrations in excess of 10 μM. We found that LSOA dimeric and trimeric compounds react with GT through a simple addition reaction resulting in formation of the carbinolamine derivative. In contrast, reactions of GT with monomeric species result in the formation of both the carbinolamine and the hydrazone derivatives. In addition, several monomers did not react with GT on the time scale of our experiment. These molecules were characterized by relatively high values of the double bond equivalent and low oxygen content. Furthermore, because addition of a charged GT tag to a neutral molecule eliminates the discrimination against the low proton affinity compounds in the ionization process, reactive nano-DESI analysis enables quantification of individual compounds in the complex mixture. For example, we were able to estimate for the first time the amounts of dimers and trimers in the LSOA mixture. Specifically, we found that the most abundant LSOA dimer was detected at the ~0.5 pg level and the total amount of dimers and trimers in the analyzed sample was ~11 pg. Our results indicate that reactive nano-DESI is a valuable approach for examining the presence of specific functional groups and for the quantification of compounds possessing

  1. Transmission geometry laser desorption atmospheric pressure photochemical ionization mass spectrometry for analysis of complex organic mixtures.

    PubMed

    Nyadong, Leonard; Mapolelo, Mmilili M; Hendrickson, Christopher L; Rodgers, Ryan P; Marshall, Alan G

    2014-11-18

    We present laser desorption atmospheric pressure photochemical ionization mass spectrometry (LD/APPCI MS) for rapid throughput analysis of complex organic mixtures, without the need for matrix, electric discharge, secondary electrospray, or solvents/vaporizers. Analytes dried on a microscope slide are vaporized in transmission geometry by a laser beam aligned with the atmospheric pressure inlet of the mass spectrometer. The laser beam initiates a cascade of reactions in the region between the glass slide and MS inlet, leading to generation of reagent ions for chemical ionization of vaporized analyte. Positive analyte ions are generated predominantly by proton transfer, charge exchange, and hydride abstraction, whereas negative ions are generated by electron capture or proton transfer reactions, enabling simultaneous analysis of saturated, unsaturated, and heteroatom-containing hydrocarbons. The absence of matrix interference renders LD/APPCI MS particularly useful for analysis of small molecules (<2000 Da) such as those present in petroleum crude oil and petroleum deposits. [M + H](+) and M(+•) dominate the positive-ion mass spectra for olefins and polyaromatic hydrocarbons, whereas saturated hydrocarbons are observed mainly as [M - H](+) and/or M(+•). Heteroatom-containing hydrocarbons are observed predominantly as [M + H](+). [M - H](-) and M(-•) are the dominant negative ions observed for analytes of lower gas-phase basicity or higher electron affinity than O2. The source was coupled with a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer (FTICR MS) to resolve and identify thousands of peaks from Athabasca bitumen heavy vacuum gas oil distillates (400-425 and 500-538 °C), enabling simultaneous characterization of their polar and nonpolar composition. We also applied LD/APPCI FTICR MS for rapid analysis of sodium and calcium naphthenate deposits with little to no sample pretreatment to provide mass spectral fingerprints that enable

  2. Thermal desorption-gas chromatography-mass spectrometry method to determine phthalate and organophosphate esters from air samples.

    PubMed

    Aragón, M; Borrull, F; Marcé, R M

    2013-08-16

    A method based on thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) has been developed to determine four organophosphate esters, seven phthalate esters, and bis(2-ethylhexyl) adipate in the gas phase from harbour and urban air samples. The method involves the sampling of 1.5L of air in a Tenax TA sorbent tube followed by thermal desorption (using a Tenax TA cryogenic trap) coupled to gas chromatography-mass spectrometry. The repeatability of the method expressed as %RSD (n=3) is less than 15% and the MQLs are between 0.007μgm(-3) (DMP, TBP, BBP, TPP and DnOP) and 6.7μgm(-3) (DEHP). The method was successfully applied in two areas (urban and harbour) testing two and three points in each one, respectively. Some of these compounds were found in both urban and harbour samples. Di-(2-ethylhexyl)phthalate was the most abundant compound found in both areas at concentration levels between 6.7μgm(-3) and 136.4μgm(-3). This study demonstrates that thermal desorption is an efficient method for the determination of these semi-volatile compounds in the gas phase fraction of air samples. PMID:23859797

  3. Surface-assisted laser desorption-ionization mass spectrometry on titanium dioxide (TiO2) nanotube layers.

    PubMed

    Piret, Gaëlle; Kim, Doohun; Drobecq, Hervé; Coffinier, Yannick; Melnyk, Oleg; Schmuki, Patrik; Boukherroub, Rabah

    2012-07-01

    The paper reports on the use of a titanium oxide (TiO(2)) nanotube layer as a sensitive substrate for surface-assisted laser desorption-ionization mass spectrometry (SALDI-MS) of peptides and small molecules. The nanotube layers were prepared by electrochemical anodization of titanium foil. The optimized TiO(2) nanotubes morphology coupled to a controlled surface chemistry allowed desorption-ionization (D/I) of a peptide mixture (Mix1) with a detection limit of 10 femtomoles for the neurotensin peptide. The performance of the TiO(2) nanotubes for the D/I of small molecules was also tested for the detection of sutent, a small tyrosine kinase inhibitor, and verapamil. A detection limit of 50 fmol was obtained for these molecules, as compared to 500 fmol using classical matrix-assisted laser desorption-ionization mass spectrometry (MALDI-MS). Both amorphous and anatase TiO(2) layers displayed a comparable performance for D/I of analyte molecules. In a control experiment, we have performed D/I of analyte molecules on a flat TiO(2) layer. The absence of signal emphasizes the role of the nanostructured substrate in the D/I process. PMID:22624145

  4. Measurement of volatile plant compounds in field ambient air by thermal desorption-gas chromatography-mass spectrometry.

    PubMed

    Cai, Xiao-Ming; Xu, Xiu-Xiu; Bian, Lei; Luo, Zong-Xiu; Chen, Zong-Mao

    2015-12-01

    Determination of volatile plant compounds in field ambient air is important to understand chemical communication between plants and insects and will aid the development of semiochemicals from plants for pest control. In this study, a thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) method was developed to measure ultra-trace levels of volatile plant compounds in field ambient air. The desorption parameters of TD, including sorbent tube material, tube desorption temperature, desorption time, and cold trap temperature, were selected and optimized. In GC-MS analysis, the selected ion monitoring mode was used for enhanced sensitivity and selectivity. This method was sufficiently sensitive to detect part-per-trillion levels of volatile plant compounds in field ambient air. Laboratory and field evaluation revealed that the method presented high precision and accuracy. Field studies indicated that the background odor of tea plantations contained some common volatile plant compounds, such as (Z)-3-hexenol, methyl salicylate, and (E)-ocimene, at concentrations ranging from 1 to 3400 ng m(-3). In addition, the background odor in summer was more abundant in quality and quantity than in autumn. Relative to previous methods, the TD-GC-MS method is more sensitive, permitting accurate qualitative and quantitative measurements of volatile plant compounds in field ambient air. PMID:26493981

  5. Nanoscale silicon surface-assisted laser desorption/ionization mass spectrometry: environment stability and activation by simple vacuum oven desiccation.

    PubMed

    Tsao, Chia-Wen; Lin, Yuan-Jing; Chen, Pi-Yu; Yang, Yu-Liang; Tan, Say Hwa

    2016-08-01

    Nanoscale silicon surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) is an emerging matrix-free, highly sensitive MS analysis method. An important challenge in using nanoscale silicon SALDI-MS analysis is the aging and stability of silicon after storage in various environments. No proper nanoscale silicon SALDI-MS activation procedure has been reported to solve this issue. This study investigated the sensitivity, wettability, and surface oxidation behavior of nanoscale silicon surface SALDI-MS in a room, an inert gas atmosphere, and a vacuum environment. A simple vacuum oven desiccation was proposed to activate the SALDI-MS surface, and the limit of detection was further enhanced 1000 times to a 500 attomole level using this approach. The long-term stability and desorption/ionization mechanism were also investigated. PMID:27315049

  6. Electron-impact ionization mass-spectrometry of molecules and clusters in a pulsed helium droplet source

    NASA Astrophysics Data System (ADS)

    Yang, Shengfu; Brereton, Scott; Ellis, Andrew M.

    2006-03-01

    A pulsed helium droplet source has been developed and characterized. The nozzle geometry was found to be critical in allowing controlled tuning of helium nanodroplet size by variation of the stagnation pressure and temperature. The average droplet size scales according to a simple p,T scaling law, placing pulsed helium nanodroplet sources on a par with cw sources for the first time. Using this pulsed source, the ability of helium nanodroplets to impede ion fragmentation in electron impact mass spectrometry has been explored. A number of haloalkanes and C1--C6 alcohols were selected as the target species. The presence of helium alters the fragmentation patterns when compared with the gas phase, with some ion product channels being more strongly affected than others. Parent ion intensities are also enhanced by the helium for alcohols, but only for the two cyclic alcohols studied, cyclopentanol and cyclohexanol, is this effect large enough to transform the parent ion from a minor product (in the gas phase) into the most abundant ion in the helium droplet experiments. The results obtained are difficult to explain solely by rapid cooling of the excited parent ions by the surrounding superfluid helium, although this undoubtedly takes place. A second factor also seems to be involved, a cage effect which favors hydrogen atom loss over other fragmentation channels.

  7. Black phosphorus-assisted laser desorption ionization mass spectrometry for the determination of low-molecular-weight compounds in biofluids.

    PubMed

    He, Xiao-Mei; Ding, Jun; Yu, Lei; Hussain, Dilshad; Feng, Yu-Qi

    2016-09-01

    Quantitative analysis of small molecules by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been a challenging task due to matrix-derived interferences in low m/z region and poor reproducibility of MS signal response. In this study, we developed an approach by applying black phosphorus (BP) as a matrix-assisted laser desorption ionization (MALDI) matrix for the quantitative analysis of small molecules for the first time. Black phosphorus-assisted laser desorption/ionization mass spectrometry (BP/ALDI-MS) showed clear background and exhibited superior detection sensitivity toward quaternary ammonium compounds compared to carbon-based materials. By combining stable isotope labeling (SIL) strategy with BP/ALDI-MS (SIL-BP/ALDI-MS), a variety of analytes labeled with quaternary ammonium group were sensitively detected. Moreover, the isotope-labeled forms of analytes also served as internal standards, which broadened the analyte coverage of BP/ALDI-MS and improved the reproducibility of MS signals. Based on these advantages, a reliable method for quantitative analysis of aldehydes from complex biological samples (saliva, urine, and serum) was successfully established. Good linearities were obtained for five aldehydes in the range of 0.1-20.0 μM with correlation coefficients (R (2)) larger than 0.9928. The LODs were found to be 20 to 100 nM. Reproducibility of the method was obtained with intra-day and inter-day relative standard deviations (RSDs) less than 10.4 %, and the recoveries in saliva samples ranged from 91.4 to 117.1 %. Taken together, the proposed SIL-BP/ALDI-MS strategy has proved to be a reliable tool for quantitative analysis of aldehydes from complex samples. Graphical Abstract An approach for the determination of small molecules was developed by using black phosphorus (BP) as a matrix-assisted laser desorption ionization (MALDI) matrix. PMID:27382971

  8. A new approach for detection of explosives based on ion mobility spectrometry and laser desorption/ionization on porous silicon

    NASA Astrophysics Data System (ADS)

    Kuzishchin, Yury; Kotkovskii, Gennadii; Martynov, Igor; Dovzhenko, Dmitriy; Chistyakov, Alexander

    2016-05-01

    We demonstrate a new way for detection ultralow concentration of explosives in this study. It combines an ion mobility spectrometry (IMS) and a promising method of laser desorption/ionization on silicon (DIOS). The DIOS is widely used in mass spectrometry due to the possibility of small molecule detection and high sensitivity. It is known that IMS based on laser ion source is a power method for the fast detection of ultralow concentration of organic molecules. However requirement of using high energy pulse ultraviolet laser increases weight and size of the device. The use of DIOS in an ion source of IMS could decrease energy pulse requirements and allows one to construct both compact and high sensitive device for analyzing gas and liquid probes. On the other hand mechanisms of DIOS in gas media is poorly studied, especially in case of nitroaromatic compounds. The investigation of the desorption/ionization on porous silicon (pSi) surface of nitroaromatic compounds has been carried out for 2,4,6-trinitrotoluene (TNT) using IMS and mass spectrometry (MS). It has been demonstrated that TNT ion formation in a gas medium is a complicated process and includes both an electron emission from the pSi surface with subsequent ion-molecular reactions in a gas phase and a proton transfer between pSi surface and TNT molecule.

  9. Nanometer scale elemental analysis in the helium ion microscope using time of flight spectrometry.

    PubMed

    Klingner, N; Heller, R; Hlawacek, G; von Borany, J; Notte, J; Huang, J; Facsko, S

    2016-03-01

    Time of flight backscattering spectrometry (ToF-BS) was successfully implemented in a helium ion microscope (HIM). Its integration introduces the ability to perform laterally resolved elemental analysis as well as elemental depth profiling on the nm scale. A lateral resolution of ≤54nm and a time resolution of Δt≤17ns(Δt/t≤5.4%) are achieved. By using the energy of the backscattered particles for contrast generation, we introduce a new imaging method to the HIM allowing direct elemental mapping as well as local spectrometry. In addition laterally resolved time of flight secondary ion mass spectrometry (ToF-SIMS) can be performed with the same setup. Time of flight is implemented by pulsing the primary ion beam. This is achieved in a cost effective and minimal invasive way that does not influence the high resolution capabilities of the microscope when operating in standard secondary electron (SE) imaging mode. This technique can thus be easily adapted to existing devices. The particular implementation of ToF-BS and ToF-SIMS techniques are described, results are presented and advantages, difficulties and limitations of this new techniques are discussed. PMID:26725148

  10. Collection method for chemical particulates on surfaces with detection using thermal desorption-ion trap mass spectrometry.

    PubMed

    Ewing, K J; Gibson, D; Sanghera, J; Miklos, F

    2013-05-01

    Successful analysis of particulate/low vapor pressure analytes such as explosives and toxic chemicals, and commercial pesticides require new sampling tools that enable detection of these analytes using current vapor phase detection instruments. We describe a sampling approach that uses stainless steel screens coated with a sticky polydimethyl siloxane (PDMS) coating to capture particulates from surfaces. Preliminary results for the collection of dimethyl methylphosphonate (DMMP) sorbed onto silica gel (SG) particulates (DMMP/SG) from a surface with subsequent analysis by thermal desorption-cylindrical ion trap mass spectrometry (TD-CITMS) are reported. PMID:23601282

  11. Few layer graphene matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Cho, Donghyun; Hong, Sangsu; Shim, Sangdeok

    2013-08-01

    We present the employment of few layer graphene (FLG) as a matrix for the analysis of low molecular weight polymeric compounds using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The practicality of FLG as a matrix for MALDI experiments is demonstrated by analyzing low molecular weight polymers, polar polyethylene glycol (PEG) of 1000 Da and nonpolar polymethylmethacrylate (PMMA) of 650 Da. The high quality MS spectra without low-mass interference signals without any further sampling procedure were acquired. PMID:23882840

  12. Rapid characterization of polyalcohols by silylation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Adeuya, Anthony; Price, Neil

    2007-01-01

    A matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry method for rapidly enumerating hydroxyl groups in analytes is described, and applied to some common polyalcohols (erythritol, mannitol and xylitol). Polyalcohols were derivatized with trimethylsilylimidazole (TMSI) either separately or as mixtures, and were analyzed, without chromatographic separation or purification. The mass spectra revealed consecutive peaks that are separated by 72 m/z units as a consequence of displacement of one hydroxyl hydrogen atom by one TMS group. The number of observed peaks was used to confirm the number of hydroxyl groups in each analyte. PMID:17994528

  13. Analysis of fatty acids by graphite plate laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Park, K H; Kim, H J

    2001-01-01

    Fatty acids obtained from triglycerides (trioelin, tripalmitin), foods (milk, corn oil), and phospholipids (phosphotidylcholine, phosphotidylserine, phosphatidic acid) upon alkaline hydrolysis were observed directly without derivatization by graphite plate laser desorption/ionization time-of-flight mass spectrometry (GPLDI-TOFMS). Mass-to-charge ratios predicted for sodium adducts of expected fatty acids (e.g. palmitic, oleic, linoleic and arachidonic acids) were observed without interference. Although at present no quantitation is possible, the graphite plate method enables a simple and rapid qualitative analysis of fatty acids. PMID:11507764

  14. Organic chemical analysis on a microscopic scale using two-step laser desorption/laser ionization mass spectrometry

    NASA Technical Reports Server (NTRS)

    Kovalenko, L. J.; Philippoz, J.-M.; Bucenell, J. R.; Zenobi, R.; Zare, R. N.

    1991-01-01

    The distribution of PAHs in the Allende meteorite has been measured using two-step laser desorption and laser multiphoton-ionization mass spectrometry. This method enables in situ analysis (with a spatial resolution of 1 mm or better) of selected organic molecules. Results show that PAH concentrations are locally high compared to the average concentration found by analysis of pulverized samples, and are found primarily in the fine-grained matrix; no PAHs were detected in the interiors of individual chondrules at the detection limit (about 0.05 ppm).

  15. Enhanced capabilities for imaging gangliosides in murine brain with matrix-assisted laser desorption/ionization and desorption electrospray ionization mass spectrometry coupled to ion mobility separation.

    PubMed

    Škrášková, Karolina; Claude, Emmanuelle; Jones, Emrys A; Towers, Mark; Ellis, Shane R; Heeren, Ron M A

    2016-07-15

    The increased interest in lipidomics calls for improved yet simplified methods of lipid analysis. Over the past two decades, mass spectrometry imaging (MSI) has been established as a powerful technique for the analysis of molecular distribution of a variety of compounds across tissue surfaces. Matrix-assisted laser desorption/ionization (MALDI) MSI is widely used to study the spatial distribution of common lipids. However, a thorough sample preparation and necessity of vacuum for efficient ionization might hamper its use for high-throughput lipid analysis. Desorption electrospray ionization (DESI) is a relatively young MS technique. In DESI, ionization of molecules occurs under ambient conditions, which alleviates sample preparation. Moreover, DESI does not require the application of an external matrix, making the detection of low mass species more feasible due to the lack of chemical matrix background. However, irrespective of the ionization method, the final information obtained during an MSI experiment is very complex and its analysis becomes challenging. It was shown that coupling MSI to ion mobility separation (IMS) simplifies imaging data interpretation. Here we employed DESI and MALDI MSI for a lipidomic analysis of the murine brain using the same IMS-enabled instrument. We report for the first time on the DESI IMS-MSI of multiply sialylated ganglioside species, as well as their acetylated versions, which we detected directly from the murine brain tissue. We show that poly-sialylated gangliosides can be imaged as multiply charged ions using DESI, while they are clearly separated from the rest of the lipid classes based on their charge state using ion mobility. This represents a major improvement in MSI of intact fragile lipid species. We additionally show that complementary lipid information is reached under particular conditions when DESI is compared to MALDI MSI. PMID:26922843

  16. Surface analysis using a new plasma assisted desorption/ionisation source for mass spectrometry in ambient air

    NASA Astrophysics Data System (ADS)

    Bowfield, A.; Barrett, D. A.; Alexander, M. R.; Ortori, C. A.; Rutten, F. M.; Salter, T. L.; Gilmore, I. S.; Bradley, J. W.

    2012-06-01

    The authors report on a modified micro-plasma assisted desorption/ionisation (PADI) device which creates plasma through the breakdown of ambient air rather than utilising an independent noble gas flow. This new micro-PADI device is used as an ion source for ambient mass spectrometry to analyse species released from the surfaces of polytetrafluoroethylene, and generic ibuprofen and paracetamol tablets through remote activation of the surface by the plasma. The mass spectra from these surfaces compare favourably to those produced by a PADI device constructed using an earlier design and confirm that the new ion source is an effective device which can be used to achieve ambient mass spectrometry with improved spatial resolution.

  17. Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry for the Discrimination of Food-Borne Microorganisms

    PubMed Central

    Mazzeo, Maria Fiorella; Sorrentino, Alida; Gaita, Marcello; Cacace, Giuseppina; Di Stasio, Michele; Facchiano, Angelo; Comi, Giuseppe; Malorni, Antonio; Siciliano, Rosa Anna

    2006-01-01

    A methodology based on matrix-assisted laser desorption ionization-time of flight mass spectrometry of intact bacterial cells was used for rapid discrimination of 24 bacterial species, and detailed analyses to identify Escherichia coli O157:H7 were carried out. Highly specific mass spectrometric profiles of pathogenic and nonpathogenic bacteria that are well-known major food contaminants were obtained, uploaded in a specific database, and made available on the Web. In order to standardize the analytical protocol, several experimental, sample preparation, and mass spectrometry parameters that can affect the reproducibility and accuracy of data were evaluated. Our results confirm the conclusion that this strategy is a powerful tool for rapid and accurate identification of bacterial species and that mass spectrometric methodologies could play an essential role in polyphasic approaches to the identification of pathogenic bacteria. PMID:16461665

  18. Aptamer Conjugated Multifunctional Nanoflowers as a Platform for Targeting, Capture and Detection in Laser Desorption Ionization Mass Spectrometry

    PubMed Central

    Ocsoy, Ismail; Gulbakan, Basri; Shukoor, Mohammed Ibrahim; Xiong, Xiangling; Chen, Tao; Powell, David H.; Tan, Weihong

    2013-01-01

    Although many different nanomaterials have been tested as substrates for laser desorption and ionization mass spectrometry (LDI-MS), this emerging field still requires more efficient multifuncional nanomaterials for targeting, enrichment and detection. Here, we report the use of gold-manganese oxide (Au@MnO) hybrid nanoflowers as an efficient matrix for LDI–MS. The nanoflowers were also functionalized with two different aptamers to target cancer cells and capture adenosine triphosphate (ATP), respectively. These nanoflowers were successfully used for metabolite extraction from cancer cell lysates. Thus, in one system, our multifunctional nanoflowers can 1) act as an ionization substrate for mass spectrometry, 2) target cancer cells, and 3) detect and analyze metabolites from cancer cells. PMID:23211039

  19. Matrix-assisted laser desorption/ionisation mass spectrometry imaging and its development for plant protein imaging

    PubMed Central

    2011-01-01

    Matrix-Assisted Laser Desorption/Ionisation (MALDI) mass spectrometry imaging (MSI) uses the power of high mass resolution time of flight (ToF) mass spectrometry coupled to the raster of lasers shots across the cut surface of tissues to provide new insights into the spatial distribution of biomolecules within biological tissues. The history of this technique in animals and plants is considered and the potential for analysis of proteins by this technique in plants is discussed. Protein biomarker identification from MALDI-MSI is a challenge and a number of different approaches to address this bottleneck are discussed. The technical considerations needed for MALDI-MSI are reviewed and these are presented alongside examples from our own work and a protocol for MALDI-MSI of proteins in plant samples. PMID:21726462

  20. Detection of native protein ions in aqueous solution under ambient conditions by electrospray laser desorption/ionization mass spectrometry.

    PubMed

    Shiea, Jentaie; Yuan, Cheng-Hui; Huang, Min-Zong; Cheng, Sy-Chyi; Ma, Ya-Lin; Tseng, Wei-Lung; Chang, Hui-Chiu; Hung, Wen-Chun

    2008-07-01

    Liquid electrospray laser desorption/ionization (ELDI) mass spectrometry allows desorption and ionization of proteins directly from aqueous solutions and biological fluids under ambient conditions. Native protein ions such as those of myoglobin, cytochrome c, and hemoglobin were obtained. A droplet (ca. 5 microL) containing the protein molecules and micrometer-sized particles (e.g., carbon graphite powder) is irradiated with a pulsed UV laser. The laser energy adsorbed by the inert particles is transferred to the surrounding solvent and protein molecules, leading to their desorption; the desorbed gaseous molecules are then postionized within an electrospray (ESI) plume to generate the ESI-like protein ions. With the use of this technique, we detected only the protonated protein ions in various biological fluids (including human tears, cow milk, serum, and bacterial extracts) without interference from their corresponding sodiated or potassiated adduct ions. In addition, we rapidly quantified the levels of glycosylated hemoglobin present in drops of whole blood obtained from diabetic patients without the need of sample pretreatment. PMID:18510347

  1. Electrospun Nanofiber Mats as "Smart Surfaces" for Desorption Electrospray Ionization Mass Spectrometry (DESI MS)-Based Analysis and Imprint Imaging.

    PubMed

    Hemalatha, R G; Ganayee, Mohd Azhardin; Pradeep, T

    2016-06-01

    In this paper, desorption electrospray ionization mass spectrometry (DESI MS)-based molecular analysis and imprint imaging using electrospun nylon-6 nanofiber mats are demonstrated for various analytical contexts. Uniform mats of varying thicknesses composed of ∼200 nm diameter fibers were prepared using needleless electrospinning. Analytical applications requiring rapid understanding of the analytes in single drops, dyes, inks, and/or plant extracts incorporated directly into the nanofibers are discussed with illustrations. The possibility to imprint patterns made of printing inks, plant parts (such as petals, leaves, and slices of rhizomes), and fungal growth on fruits with their faithful reproductions on the nanofiber mats is illustrated with suitable examples. Metabolites were identified by tandem mass spectrometry data available in the literature and in databases. The results highlight the significance of electrospun nanofiber mats as smart surfaces to capture diverse classes of compounds for rapid detection or to imprint imaging under ambient conditions. Large surface area, appropriate chemical functionalities exposed, and easiness of desorption due to weaker interactions of the analyte species are the specific advantages of nanofibers for this application. PMID:27159150

  2. Detection of trace organics in Mars analog samples containing perchlorate by laser desorption/ionization mass spectrometry.

    PubMed

    Li, Xiang; Danell, Ryan M; Brinckerhoff, William B; Pinnick, Veronica T; van Amerom, Friso; Arevalo, Ricardo D; Getty, Stephanie A; Mahaffy, Paul R; Steininger, Harald; Goesmann, Fred

    2015-02-01

    Evidence from recent Mars missions indicates the presence of perchlorate salts up to 1 wt % level in the near-surface materials. Mixed perchlorates and other oxychlorine species may complicate the detection of organic molecules in bulk martian samples when using pyrolysis techniques. To address this analytical challenge, we report here results of laboratory measurements with laser desorption mass spectrometry, including analyses performed on both commercial and Mars Organic Molecule Analyzer (MOMA) breadboard instruments. We demonstrate that the detection of nonvolatile organics in selected spiked mineral-matrix materials by laser desorption/ionization (LDI) mass spectrometry is not inhibited by the presence of up to 1 wt % perchlorate salt. The organics in the sample are not significantly degraded or combusted in the LDI process, and the parent molecular ion is retained in the mass spectrum. The LDI technique provides distinct potential benefits for the detection of organics in situ on the martian surface and has the potential to aid in the search for signs of life on Mars. PMID:25622133

  3. Development of matrix-assisted ultraviolet laser desorption/ionization mass spectrometry for the structural analysis of glycoproteins

    SciTech Connect

    Chevrier, M.R.

    1993-01-01

    This thesis describes the design, construction and characterization of an ultraviolet laser desorption time-of-flight [TOF] mass spectrometer and its subsequent application to glycoprotein structural analysis utilizing matrix-assisted laser desorption/ionization [MALDI] mass spectrometry. At the inception of this work, commercial mass spectrometers utilizing MALDI were not available, and most reports of the phenomena utilized the 266 nm wavelength provided by frequency-quadrupled Nd:YAG lasers. This work involved the design and construction of a high-voltage-extraction linear TOF mass analyzer equipped with a multiple sample inlet system and a 337 manometer, 600 picosecond pulsed nitrogen laser. In MALDI the [open quotes]matrix[close quotes], a strong absorber of a laser wavelength, is co-crystallized with the analyte. The laser photons absorbed by the matrix lead to ionization of the analyte and subsequent desorption from the surface into the gas phase. While nicotinic acid and caffeic acid were reported as effective matrices at 266 and 355 nm, respectively, several other matrices were examined for their efficiency at 337 nm, including [alpha]-cyano-4-hydroxy cinnamic acid and gentisic acid, which proved to be advantageous for glycoconjugate analysis. Glycoproteins, phosphoproteins, nucleic acids, and proteolytic digests were all successfully analyzed using the pulsed nitrogen laser. Analysis of numerous peptides and proteins demonstrated femtomolar sensitivity, mass range in excess of 350 kiloDaltons, mass resolution circa 700, and mass accuracy better than 0.1%. The completed instrument was utilized to analyze glycopeptides for carbohydrate sites and microheterogeneity, by performing MALDI mass spectrometry [MALDI/MS] following enzymatic and chemical reactions. In many cases, unfractionated or partially fractionated mixtures were analyzed directly thereby reducing preparative chromatography.

  4. Laser desorption/ionization mass spectrometry on nanostructured semiconductor substrates: DIOS(TM) and QuickMass(TM)

    NASA Astrophysics Data System (ADS)

    Law, K. P.

    2010-02-01

    In the era of systems biology, new analytical platforms are under demand. Desorption/ionization on silicon mass spectrometry (DIOS-MS) is a promising high throughput laser mass spectrometry approach that has attracted a lot of attention, and has been commercialized. Another substrate material manufactured by physical method has also been made commercially available under the trade name of QuickMass(TM). These two commercial substrates, DIOS(TM) and QuickMass(TM), were investigated independently from the manufacturers and were characterized by a number of advanced surface techniques. This work determined (1) the correlation between the substrate physicochemical properties and their LDI activity, (2) the feasibility of metabolic profiling from complex biological matrices and (3) the laser desorption/ionization mechanism. The DIOS(TM) substrate was characterized with a thick nano-sized porous layer, a high surface concentration of fluorocarbon and silicon oxides and super-hydrophobicity. In contrast, the QuickMass(TM) substrate consisted of a non-porous germanium thin-film. The relatively high ionization efficiency obtained from the DIOS(TM) substrate was contributed to the fluorosilane manufacturing processes and its porous morphology. Despite the QuickMass(TM) substrate being less effective, it was noted that the use of germanium affords a self-cleaning mechanism and suppresses background interference of mass spectra. The suitability of DIOS(TM) substrates for metabolic profiling of complex biological matrices was demonstrated. DIOS mass spectra of human blood plasma, human urine and animal liver tissue extracts were produced. Suitable extraction methods were found to be important, but relatively simplified approaches were sufficient. Further investigations of the DIOS desorption/ionization mechanism were carried out. The previously proposed sub-surface state reaction could be a molten-solid interfacial state reaction of the substrate and this had a significant

  5. Whole-body Mass Spectrometry Imaging by Infrared Matrix-assisted Laser Desorption Electrospray Ionization (IR-MALDESI).

    PubMed

    Nazari, Milad; Bokhart, Mark T; Muddiman, David C

    2016-01-01

    Ambient ionization sources for mass spectrometry (MS) have been the subject of much interest in the past decade. Matrix-assisted laser desorption electrospray ionization (MALDESI) is an example of such methods, where features of matrix-assisted laser desorption/ionization (MALDI) (e.g., pulsed nature of desorption) and electrospray ionization (ESI) (e.g., soft-ionization) are combined. One of the major advantages of MALDESI is its inherent versatility. In MALDESI experiments, an ultraviolet (UV) or infrared (IR) laser can be used to resonantly excite an endogenous or exogenous matrix. The choice of matrix is not analyte dependent, and depends solely on the laser wavelength used for excitation. In IR-MALDESI experiments, a thin layer of ice is deposited on the sample surface as an energy-absorbing matrix. The IR-MALDESI source geometry has been optimized using statistical design of experiments (DOE) for analysis of liquid samples as well as biological tissue specimens. Furthermore, a robust IR-MALDESI imaging source has been developed, where a tunable mid-IR laser is synchronized with a computer controlled XY translational stage and a high resolving power mass spectrometer. A custom graphical user interface (GUI) allows user selection of the repetition rate of the laser, number of shots per voxel, step-size of the sample stage, and the delay between the desorption and scan events for the source. IR-MALDESI has been used in variety of applications such as forensic analysis of fibers and dyes and MSI of biological tissue sections. Distribution of different analytes ranging from endogenous metabolites to exogenous xenobiotics within tissue sections can be measured and quantified using this technique. The protocol presented in this manuscript describes major steps necessary for IR-MALDESI MSI of whole-body tissue sections. PMID:27077488

  6. Nanospray Desorption Electrospray Ionization: an Ambient Method for Liquid-Extraction Surface Sampling in Mass Spectrometry

    SciTech Connect

    Roach, Patrick J.; Laskin, Julia; Laskin, Alexander

    2010-08-17

    A novel nanospray desorption electrospray ionization (nano-DESI) approach is presented and its analytical applications are demonstrated for trace analysis of complex organic analytes deposited on substrates. In this approach the analyte is probed by a micro-droplet of charged solvent formed at the junction between two capillaries. One primary capillary is used to create and maintain a charged micro-droplet of solvent on the substrate while a second capillary is used to create a self-aspirating nanospray that delivers solvent dissolved analyte to the inlet of a mass spectrometer. This approach enables efficient separation of desorption and ionization events, thus providing better control over transport and ionization of the analyte. In this letter we present the basics of the nano-DESI approach and demonstrate its analytical capabilities. Specifically, we demonstrate significant improvement of the limits of detection and the stability of the signal as compared to the traditional DESI and discuss imaging applications.

  7. High-Resolution Live-Cell Imaging and Analysis by Laser Desorption/Ionization Droplet Delivery Mass Spectrometry.

    PubMed

    Lee, Jae Kyoo; Jansson, Erik T; Nam, Hong Gil; Zare, Richard N

    2016-05-17

    We have developed a new ambient-ionization mass spectrometric technique named laser desorption/ionization droplet delivery mass spectrometry (LDIDD-MS). LDIDD-MS permits high-resolution, high-sensitivity imaging of tissue samples as well as measurements of both single-cell apoptosis and live-cell exocytosis. A pulsed (15 Hz) UV laser beam (266 nm) is focused on a surface covered with target analytes to trigger their desorption and ionization. A spray of liquid droplets is simultaneously directed onto the laser-focused surface region to capture the ionized analytes and deliver them to a mass spectrometer. The approach of rapid and effective capturing of molecules after laser desorption/ionization allows the limit of detection for the amino acid lysine to be as low as 2 amol under ambient ionization conditions. Two-dimensional maps of the desorbed/ionized species are recorded by moving the sample on an XY translational stage. The spatial resolution for imaging with LDIDD-MS was determined to be 2.4 μm for an ink-printed pattern and 3 μm for mouse brain tissue. We applied LDIDD-MS to single-cell analysis of apoptotic HEK cells. Differences were observed in the profiles of fatty acids and lipids between healthy HEK cells and those undergoing apoptosis. We observed upregulation of phosphatidylcholine (PC) with a relatively shorter carbon chain length and downregulation of PC with a relatively longer carbon chain length. We also applied LDIDD-MS for a real-time direct measurements of live-cell exocytosis. The catecholamine dopamine and trace amines (phenethylamine and tyramine) were detected from live PC12 cells without damaging them. PMID:27110027

  8. Matrix assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) for direct visualization of plant metabolites in situ.

    PubMed

    Sturtevant, Drew; Lee, Young-Jin; Chapman, Kent D

    2016-02-01

    Direct visualization of plant tissues by matrix assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) has revealed key insights into the localization of metabolites in situ. Recent efforts have determined the spatial distribution of primary and secondary metabolites in plant tissues and cells. Strategies have been applied in many areas of metabolism including isotope flux analyses, plant interactions, and transcriptional regulation of metabolite accumulation. Technological advances have pushed achievable spatial resolution to subcellular levels and increased instrument sensitivity by several orders of magnitude. It is anticipated that MALDI-MSI and other MSI approaches will bring a new level of understanding to metabolomics as scientists will be encouraged to consider spatial heterogeneity of metabolites in descriptions of metabolic pathway regulation. PMID:26613199

  9. Matrix assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) for direct visualization of plant metabolites in situ

    DOE PAGESBeta

    Sturtevant, Drew; Lee, Young -Jin; Chapman, Kent D.

    2015-11-22

    Direct visualization of plant tissues by matrix assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) has revealed key insights into the localization of metabolites in situ. Recent efforts have determined the spatial distribution of primary and secondary metabolites in plant tissues and cells. Strategies have been applied in many areas of metabolism including isotope flux analyses, plant interactions, and transcriptional regulation of metabolite accumulation. Technological advances have pushed achievable spatial resolution to subcellular levels and increased instrument sensitivity by several orders of magnitude. Furthermore, it is anticipated that MALDI-MSI and other MSI approaches will bring a new level of understanding tomore » metabolomics as scientists will be encouraged to consider spatial heterogeneity of metabolites in descriptions of metabolic pathway regulation.« less

  10. 5-Methoxysalicylic Acid Matrix for Ganglioside Analysis with Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Lee, Dongkun; Cha, Sangwon

    2015-03-01

    In this note, we report that high quality ganglioside profiles with minimal loss of sialic acid residues can be obtained in the positive ion mode by using a 5-methoxysalicylic acid (MSA) matrix for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Our results showed that MSA produced much less sialic acid losses from gangliosides than DHB, although MSA and DHB are differ only by their functional groups at their 5-positions (-OH for DHB and -OCH3 for MSA). Furthermore, our data also demonstrated that addition of an alkali metal additive was effective for simplifying ganglioside profiles, but not necessary for stabilizing glycosidic bonds of gangliosides if MSA was used as a matrix. This suggests that MALDI MS with MSA has a potential to gain additional benefits from the positive-ion mode analyses without losing performance in ganglioside profiling.

  11. Analysis and Quantitation of Glycated Hemoglobin by Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Hattan, Stephen J.; Parker, Kenneth C.; Vestal, Marvin L.; Yang, Jane Y.; Herold, David A.; Duncan, Mark W.

    2016-03-01

    Measurement of glycated hemoglobin is widely used for the diagnosis and monitoring of diabetes mellitus. Matrix assisted laser desorption/ionization (MALDI) time of flight (TOF) mass spectrometry (MS) analysis of patient samples is used to demonstrate a method for quantitation of total glycation on the β-subunit of hemoglobin. The approach is accurate and calibrated with commercially available reference materials. Measurements were linear (R2 > 0.99) across the clinically relevant range of 4% to 20% glycation with coefficients of variation of ≤ 2.5%. Additional and independent measurements of glycation of the α-subunit of hemoglobin are used to validate β-subunit glycation measurements and distinguish hemoglobin variants. Results obtained by MALDI-TOF MS were compared with those obtained in a clinical laboratory using validated HPLC methodology. MALDI-TOF MS sample preparation was minimal and analysis times were rapid making the method an attractive alternative to methodologies currently in practice.

  12. Methane ice photochemistry and kinetic study using laser desorption time-of-flight mass spectrometry at 20 K.

    PubMed

    Bossa, J-B; Paardekooper, D M; Isokoski, K; Linnartz, H

    2015-07-14

    The ice photochemistry of pure methane (CH4) is studied at 20 K upon VUV irradiation from a microwave discharge H2 flow lamp. Laser Desorption Post-Ionization Time-Of-Flight Mass Spectrometry (LDPI TOF-MS) is used for the first time to determine branching ratios of primary reactions leading to CH3, CH2, and CH radicals, typically for fluences as expected in space. This study is based on a stable end-products analysis and the mass spectra are interpreted using an appropriate set of coupled reactions and rate constants. This yields clearly different values from previous gas phase studies. The matrix environment as well as the higher efficiency of reverse reactions in the ice clearly favor CH3 radical formation as the main first generation photoproduct. PMID:26073296

  13. Structural characterization of phospholipids by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Marto, J A; White, F M; Seldomridge, S; Marshall, A G

    1995-11-01

    Matrix-assisted laser desorption/ionization (MALDI) Fourier transform ion cyclotron resonance mass spectrometry provides for structural analysis of the principal biological phospholipids: glycerophosphatidylcholine, -ethanolamine, -serine, and -inositol. Both positive and negative molecular or quasimolecular ions are generated in high abundance. Isolated molecular ions may be collisionally activated in the source side of a dual trap mass analyzer, yielding fragments serving to identify the polar head group (positive ion mode) and fatty acid side chains (negative ion mode). Azimuthal quadrupolar excitation following collisionally activated dissociation refocuses productions close to the solenoid axis; subsequent transfer of product ions to the analyzer ion trap allows for high-resolution mass analysis. Cyro-cooling of the sample probe with liquid nitrogen greatly reduces matrix adduction encountered in the negative ion mode. PMID:8633761

  14. Recent Advances in Bacteria Identification by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Using Nanomaterials as Affinity Probes

    PubMed Central

    Chiu, Tai-Chia

    2014-01-01

    Identifying trace amounts of bacteria rapidly, accurately, selectively, and with high sensitivity is important to ensuring the safety of food and diagnosing infectious bacterial diseases. Microbial diseases constitute the major cause of death in many developing and developed countries of the world. The early detection of pathogenic bacteria is crucial in preventing, treating, and containing the spread of infections, and there is an urgent requirement for sensitive, specific, and accurate diagnostic tests. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is an extremely selective and sensitive analytical tool that can be used to characterize different species of pathogenic bacteria. Various functionalized or unmodified nanomaterials can be used as affinity probes to capture and concentrate microorganisms. Recent developments in bacterial detection using nanomaterials-assisted MALDI-MS approaches are highlighted in this article. A comprehensive table listing MALDI-MS approaches for identifying pathogenic bacteria, categorized by the nanomaterials used, is provided. PMID:24786089

  15. Rapid identification of haloarchaea and methanoarchaea using the matrix assisted laser desorption/ionization time-of-flight mass spectrometry

    PubMed Central

    Shih, Chao-Jen; Chen, Sheng-Chung; Weng, Chieh-Yin; Lai, Mei-Chin; Yang, Yu-Liang

    2015-01-01

    The aim of this study was to classify certain environmental haloarchaea and methanoarchaea using matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and to expand the archaeal mass spectral database. A total of 69 archaea were collected including type strains and samples isolated locally from different environments. For extraction of the haloarchaeal total cell peptides/proteins, a simple method of acetonitrile extraction was developed. Cluster analysis conducted with the MALDI-TOF MS data overcame the high divergence in intragenomic 16S rRNA sequences in haloarchaea and clearly distinguished Methanohalophilus mahii from M. portucalensis. Putative biomarkers that can distinguish several particular archaeal genera were also assigned. In conclusion, this study expands the mass spectral database of peptide/protein fingerprints from bacteria and fungi to the archaea domain and provides a rapid identification platform for environmental archaeal samples. PMID:26541644

  16. On plate graphite supported sample processing for simultaneous lipid and protein identification by matrix assisted laser desorption ionization mass spectrometry.

    PubMed

    Calvano, Cosima Damiana; van der Werf, Inez Dorothé; Sabbatini, Luigia; Palmisano, Francesco

    2015-05-01

    The simultaneous identification of lipids and proteins by matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) after direct on-plate processing of micro-samples supported on colloidal graphite is demonstrated. Taking advantages of large surface area and thermal conductivity, graphite provided an ideal substrate for on-plate proteolysis and lipid extraction. Indeed proteins could be efficiently digested on-plate within 15 min, providing sequence coverages comparable to those obtained by conventional in-solution overnight digestion. Interestingly, detection of hydrophilic phosphorylated peptides could be easily achieved without any further enrichment step. Furthermore, lipids could be simultaneously extracted/identified without any additional treatment/processing step as demonstrated for model complex samples such as milk and egg. The present approach is simple, efficient, of large applicability and offers great promise for protein and lipid identification in very small samples. PMID:25770620

  17. Rapid analysis of animal drug residues by microcolumn solid-phase extraction and thermal desorption-ion trap mass spectrometry

    SciTech Connect

    Barshick, S.A.; Buchanan, M.V.

    1994-11-01

    A new approach was developed for the rapid and quantitative determination of an anthelmintic drug, phenothiazine, in milk. The technique involves a simple extraction procedure using a C{sub 18} microcolumn disc, followed by thermal desorption of the analyte from the disc directly into an ion trap mass spectrometer. The compounds are selectively ionized by isobutane chemical ionization and detected by tandem mass spectrometry. With this approach, 10 ppb detection limits were achieved with as little as 100 {mu}L mild and only 10 min of analysis time. This approach was used to analyze samples of milk taken from a cow administered a one-time therapeutic dose of phenothiazine. The target compound could be detected at 56 post-dosage, corresponding to a concentration of 30 ppb. 13 refs., 3 figs., 2 tabs.

  18. Analysis of polycyclic aromatic hydrocarbons (PAHs) using nanosecond laser desorption/femtosecond ionization laser mass spectrometry (FLMS)

    NASA Astrophysics Data System (ADS)

    Robson, L.; Tasker, A. D.; Hankin, S. M.; Ledingham, K. W. D.; Singhal, R. P.; Fang, X.; McCanny, T.; Kosmidis, C.; Tzallas, P.; Langley, A. J.; Taday, P. F.; Divall, E. J.

    2001-08-01

    Nanosecond laser desorption/femtosecond ionization laser mass spectrometry (LD/FLMS) allows ultra-sensitive detection and trace analysis of atoms and molecules. In this study, we have applied the LD/FLMS technique to the characterization of polycyclic aromatic hydrocarbons (PAHs). Using high intensity femtosecond laser pulses (1013-1015 W/cm2) at λ˜395 nm and 790nm coupled to a reflectron time of flight mass spectrometer a series of PAHs have been investigated. In particular, anthracene, tetracene and pentacene are discussed. The spectra presented show intact parent ion at both wavelengths, with little fragmentation at lower ionization laser intensities. This initial data suggests that the optimum wavelength to operate FLMS for PAHs may be 395 nm and not 790 nm for maximum parent ion production. Comparative studies adopting nanosecond ionization are also discussed.

  19. Screening of the Binding of Small Molecules to Proteins by Desorption Electrospray Ionization Mass Spectrometry Combined with Protein Microarray

    NASA Astrophysics Data System (ADS)

    Yao, Chenxi; Wang, Tao; Zhang, Buqing; He, Dacheng; Na, Na; Ouyang, Jin

    2015-11-01

    The interaction between bioactive small molecule ligands and proteins is one of the important research areas in proteomics. Herein, a simple and rapid method is established to screen small ligands that bind to proteins. We designed an agarose slide to immobilize different proteins. The protein microarrays were allowed to interact with different small ligands, and after washing, the microarrays were screened by desorption electrospray ionization mass spectrometry (DESI MS). This method can be applied to screen specific protein binding ligands and was shown for seven proteins and 34 known ligands for these proteins. In addition, a high-throughput screening was achieved, with the analysis requiring approximately 4 s for one sample spot. We then applied this method to determine the binding between the important protein matrix metalloproteinase-9 (MMP-9) and 88 small compounds. The molecular docking results confirmed the MS results, demonstrating that this method is suitable for the rapid and accurate screening of ligands binding to proteins.

  20. Rapid screening of illicit additives in weight loss dietary supplements with desorption corona beam ionisation (DCBI) mass spectrometry.

    PubMed

    Wang, H; Wu, Y; Zhao, Y; Sun, W; Ding, L; Guo, B; Chen, B

    2012-08-01

    Desorption corona beam ionisation (DCBI), the relatively novel ambient mass spectrometry (MS) technique, was utilised to screen for illicit additives in weight-loss food. The five usually abused chemicals - fenfluramine, N-di-desmethyl sibutramine, N-mono-desmethyl sibutramine, sibutramine and phenolphthalein - were detected with the proposed DCBI-MS method. Fast single-sample and high-throughput analysis was demonstrated. Semi-quantification was accomplished based on peak areas in the ion chromatograms. Four illicit additives were identified and semi-quantified in commercial samples. As there was no tedious sample pre-treatment compared with conventional HPLC methods, high-throughput analysis was achieved with DCBI. The results proved that DCBI-MS is a powerful tool for the rapid screening of illicit additives in weight-loss dietary supplements. PMID:22784191

  1. Matrix-free mass spectrometric imaging using laser desorption ionisation Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Goodwin, Richard J A; Pitt, Andrew R; Harrison, David; Weidt, Stefan K; Langridge-Smith, Pat R R; Barrett, Michael P; Logan Mackay, C

    2011-04-15

    Mass spectrometry imaging (MSI) is a powerful tool in metabolomics and proteomics for the spatial localization and identification of pharmaceuticals, metabolites, lipids, peptides and proteins in biological tissues. However, sample preparation remains a crucial variable in obtaining the most accurate distributions. Common washing steps used to remove salts, and solvent-based matrix application, allow analyte spreading to occur. Solvent-free matrix applications can reduce this risk, but increase the possibility of ionisation bias due to matrix adhesion to tissue sections. We report here the use of matrix-free MSI using laser desorption ionisation performed on a 12 T Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. We used unprocessed tissue with no post-processing following thaw-mounting on matrix-assisted laser desorption ionisation (MALDI) indium-tin oxide (ITO) target plates. The identification and distribution of a range of phospholipids in mouse brain and kidney sections are presented and compared with previously published MALDI time-of-flight (TOF) MSI distributions. PMID:21416534

  2. Cellular-level mass spectrometry imaging using infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) by oversampling.

    PubMed

    Nazari, Milad; Muddiman, David C

    2015-03-01

    Mass spectrometry imaging (MSI) allows for the direct and simultaneous analysis of the spatial distribution of molecular species from sample surfaces such as tissue sections. One of the goals of MSI is monitoring the distribution of compounds at the cellular resolution in order to gain insights about the biology that occurs at this spatial level. Infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) imaging of cervical tissue sections was performed using a spot-to-spot distance of 10 μm by utilizing the method of oversampling, where the target plate is moved by a distance that is less than the desorption radius of the laser. In addition to high spatial resolution, high mass accuracy (±1 ppm) and high mass resolving power (140,000 at m/z = 200) were achieved by coupling the IR-MALDESI imaging source to a hybrid quadrupole Orbitrap mass spectrometer. Ion maps of cholesterol in tissues were generated from voxels containing <1 cell, on average. Additionally, the challenges of imaging at the cellular level in terms of loss of sensitivity and longer analysis time are discussed. PMID:25486925

  3. [Determination of volatile organic compounds in ambient air by thermal desorption-gas chromatography-triple quadrupole tandem mass spectrometry].

    PubMed

    Feng, Lili; Hu, Xiaofang; Yu, Xiaojuan; Zhang, Wenying

    2016-02-01

    A method was established for the simultaneous determination of 23 volatile organic compounds (VOCs) in ambient air with combination of thermal desorption (TD) and gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS). The air samples were collected by active sampling method using Tenax-TA sorbent tubes, and desorbed by thermal desorption. The analytes were determined by GC-MS/MS in selected reaction monitoring (SRM) mode, and internal standard method was applied to quantify the VOCs. The results of all the 23 VOCs showed good linearities in low level (0. 01-1 ng) and high level (1-100 ng) with all the correlation coefficients (r2) more than 0. 99. The method quantification limits were between 0. 000 08-1 µg/m3. The method was validated by means of recovery experiments (n = 6) at three spiked levels of 2, 10 and 50 ng. The recoveries between 77% and 124% were generally obtained. The relative standard deviations (RSDs) in all cases were lower than 20%, except for chlorobenzene at the low spiked level. The developed method was applied to determine VOCs in ambient air collected at three sites in Shanghai. Several compounds, like benzene, toluene, ethylbenzene, m-xylenes, p-xylenes, styrene, 1, 2, 4-trimethylbenzene and hexachlorobutadiene were detected and confirmed in all the samples analyzed. The method is highly accurate, reliable and sensitive for monitoring the VOCs in ambient air. PMID:27382728

  4. Analysis of the volatile components emitted from cut tobacco processing by gas chromatography/mass spectrometry thermal desorption system.

    PubMed

    Gao, Qiang; Sha, Yunfei; Wu, Da; Liu, Baizhan; Chen, Chaoying; Fang, Dingye

    2012-11-15

    A sensitive and reliable method was developed for the determination of volatile components emitted from cut tobacco processing using thermal desorption (TD) followed by gas chromatography-mass spectrometry (GC-MS). In the work, to obtain the optimal sorbent, three commercial sorbents were compared in terms of adsorption efficiency. The carbotrap 349 was found to have the best performance. The desorption conditions were also studied. Validation of the TD-GC-MS method showed good sensibility, linearity and precision. Limits of detection ranges were from 0.20 to 3.6 ng. Calibration curves were obtained by plotting peak area versus concentration and the correlation coefficients relating to linearity were at least 0.9984. The analysis was reproducible, with relative standard deviation (n=8) within 6.5%. The target compound breakthrough examination showed no significant losses when about 1500 ng standards were prepared. In order to evaluate the performance of the analytical method in the volatile constituents of cut tobacco, samples were taken in industrial areas of cut tobacco processing. Recoveries ranged from 85.1% to 110% for all the compounds and good precision had been reached (RSD<13.3). The results proved that TD-GC-MS was a simple, rapid and accurate method for the analysis of volatile compounds emitted from cut tobacco drying step. PMID:23158312

  5. Headspace sorptive extraction for the analysis of organotin compounds using thermal desorption and gas chromatography with mass spectrometry.

    PubMed

    Cacho, J I; Campillo, N; Viñas, P; Hernández-Córdoba, M

    2013-03-01

    A method based on headspace sorptive extraction (HSSE) in combination with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) has been developed for the simultaneous determination of six organotin compounds (OTCs), corresponding to mono- and di-substituted methyltin, butyltin and octyltin species. Several parameters affecting both the headspace extraction and thermal desorption steps were carefully optimized using multivariate designs. Analytes were derivatized by in situ ethylation with sodium tetraethylborate. The optimized method was applied to the analysis of water samples of different origins, as well as to checking the migration of the studied compounds from commercially available plastic containers to the adequate liquid simulant. Quantification was carried out against aqueous calibration curves using diphenyltin as internal standard, providing detection limits of between 1.7 and 7.0 ng(Sn) L(-1), depending on the compound, and repeatabilities lower than 10% in terms of relative standard deviation. The applicability of the method was assessed by means of recovery studies and satisfactory values for all compounds were attained. The release of OTCs from the tested packages to the liquid simulant was confirmed, concentrations as high as 2.4 μg(Sn) L(-1) being found for dioctyltin. Even though the proposed method was developed for organotin halides, its application to an organotin ester shows its suitability for determining these compounds in migration assays. PMID:23357745

  6. Solvent Separating Secondary Metabolites Directly from Biosynthetic Tissue for Surface-Assisted Laser Desorption Ionisation Mass Spectrometry

    PubMed Central

    Rudd, David; Benkendorff, Kirsten; Voelcker, Nicolas H.

    2015-01-01

    Marine bioactive metabolites are often heterogeneously expressed in tissues both spatially and over time. Therefore, traditional solvent extraction methods benefit from an understanding of the in situ sites of biosynthesis and storage to deal with heterogeneity and maximize yield. Recently, surface-assisted mass spectrometry (MS) methods namely nanostructure-assisted laser desorption ionisation (NALDI) and desorption ionisation on porous silicon (DIOS) surfaces have been developed to enable the direct detection of low molecular weight metabolites. Since direct tissue NALDI-MS or DIOS-MS produce complex spectra due to the wide variety of other metabolites and fragments present in the low mass range, we report here the use of “on surface” solvent separation directly from mollusc tissue onto nanostructured surfaces for MS analysis, as a mechanism for simplifying data annotation and detecting possible artefacts from compound delocalization during the preparative steps. Water, ethanol, chloroform and hexane selectively extracted a range of choline esters, brominated indoles and lipids from Dicathais orbita hypobranchial tissue imprints. These compounds could be quantified on the nanostructured surfaces by comparison to standard curves generated from the pure compounds. Surface-assisted MS could have broad utility for detecting a broad range of secondary metabolites in complex marine tissue samples. PMID:25786067

  7. Thermally annealed gold nanoparticles for surface-assisted laser desorption ionisation-mass spectrometry of low molecular weight analytes.

    PubMed

    Pilolli, Rosa; Ditaranto, Nicoletta; Di Franco, Cinzia; Palmisano, Francesco; Cioffi, Nicola

    2012-10-01

    Metal nanomaterials have an emerging role in surface-assisted laser desorption ionisation-mass spectrometry (SALDI-MS) providing a useful tool to overcome some limitations intrinsically related to the use of conventional organic matrices in matrix-assisted LDI-MS. In this contribution, the possibility to use a stainless-steel-supported gold nanoparticle (AuNP) film as a versatile platform for SALDI-MS was assessed. A sacrificial anode electrosynthetic route was chosen in order to obtain morphologically controlled core-shell AuNPs; the colloidal AuNPs were, thereafter, drop cast onto a stainless-steel sample plate and the resulting AuNP film was thermally annealed in order to improve its effectiveness as LDI-MS promoter. Spectroscopic characterization of the nanostructured film by X-ray photoelectron spectroscopy was crucial for understanding how annealing induced changes in the surface chemistry and influenced the performance of AuNPs as desorption/ionisation promoter. In particular, it was demonstrated that the post-deposition treatments were essential to enhance the AuNP core/analyte interaction, thus resulting in SALDI-MS spectra of significantly improved quality. The AuNP films were applied to the detection of three different classes of low molecular weight (LMW) analytes, i.e. amino acids, peptides and LMW polymers, in order to demonstrate the versatility of this nanostructured material. PMID:22825677

  8. Laser desorption/ionization mass spectrometry for direct profiling and imaging of small molecules from raw biological materials

    SciTech Connect

    Cha, Sangwon

    2008-01-01

    Matrix-assisted laser desorption/ionization(MALDI) mass spectrometry(MS) has been widely used for analysis of biological molecules, especially macromolecules such as proteins. However, MALDI MS has a problem in small molecule (less than 1 kDa) analysis because of the signal saturation by organic matrixes in the low mass region. In imaging MS (IMS), inhomogeneous surface formation due to the co-crystallization process by organic MALDI matrixes limits the spatial resolution of the mass spectral image. Therefore, to make laser desorption/ionization (LDI) MS more suitable for mass spectral profiling and imaging of small molecules directly from raw biological tissues, LDI MS protocols with various alternative assisting materials were developed and applied to many biological systems of interest. Colloidal graphite was used as a matrix for IMS of small molecules for the first time and methodologies for analyses of small metabolites in rat brain tissues, fruits, and plant tissues were developed. With rat brain tissues, the signal enhancement for cerebroside species by colloidal graphite was observed and images of cerebrosides were successfully generated by IMS. In addition, separation of isobaric lipid ions was performed by imaging tandem MS. Directly from Arabidopsis flowers, flavonoids were successfully profiled and heterogeneous distribution of flavonoids in petals was observed for the first time by graphite-assisted LDI(GALDI) IMS.

  9. Cellular Level Mass Spectrometry Imaging using Infrared Matrix Assisted Laser Desorption Electrospray Ionization (IR-MALDESI) by Oversampling

    PubMed Central

    Nazari, Milad; Muddiman, David C.

    2014-01-01

    Mass spectrometry imaging (MSI) allows for the direct and simultaneous analysis of the spatial distribution of molecular species from sample surfaces such as tissue sections. One of the goals of MSI is monitoring the distribution of compounds at the cellular resolution in order to gain insights about the biology that occurs at this spatial level. Infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) imaging of cervical tissue sections was performed using a spot-to-spot distance of 10 μm by utilizing the method of oversampling; where the target plate is moved by a distance that is less than the desorption radius of the laser. In addition to high spatial resolution, high mass accuracy (± 1 ppm) and high mass resolving power (140,000 at m/z=200) was achieved by coupling the IR-MALDESI imaging source to a hybrid quadrupole Orbitrap mass spectrometer. Ion maps of cholesterol in tissues were generated from voxels containing <1 cell, on average. Additionally, the challenges of imaging at the cellular level in terms of loss of sensitivity and longer analysis time are discussed. PMID:25486925

  10. An improvement of matrix-assisted laser desorption/ionization mass spectrometry using an infrared tunable free electron laser

    NASA Astrophysics Data System (ADS)

    Naito, Yasuhide; Yoshihashi-Suzuki, Sachiko; Ishii, Katsunori; Awazu, Kunio

    2004-08-01

    Matrix-assisted laser desorption/ionization (MALDI) combined with time-of-flight mass spectrometry (TOFMS) is a powerful yet robust tool for protein identification, due to its high sensitivity and theoretically unlimited detectable mass range. A large part of functional proteins, such as membrane proteins, are insoluble as native forms in a matrix solution without a strong denaturing condition, hence are not amenable to the conventional MALDI-TOFMS analysis. Aiming at overcoming this difficulty, we have developed a novel MALDI technique (UV/FEL-MALDI). An infrared free electron laser (IR-FEL) has a wide tunability in a mid-IR range and is quite attractive as a source of selective vibrational excitation. The FEL wavelength can be tuned to activate a denaturant, which impedes the conventional MALDI process, without an excess heating of analyte molecules. This scheme lets a dense denaturant to be used for the MALDI sample preparation of insoluble proteins. A simultaneous use of the FEL with a nitrogen pulse laser for MALDI achieves spatially and temporally defined desorption, which is essential to TOFMS detection, while specificity and selectivity owing to an FEL wavelength can be conserved. Some attractive features of the protein clustering have been found in the application of UV/FEL-MALDI to hair keratins, which was chosen as a model of insoluble proteins.