Organic Mass Spectrometry Research Articles

Organic Mass Spectrometry in Art and Archaeology

Organic Mass Spectrometry in Art and Archaeology

Organic Secondary Ion Mass Spectrometry: Signal Enhancement by Water Vapor Injection

The enhancement of the static secondary ion mass spectrometry (SIMS) signals resulting from the injection, closely to the sample surface, of H(2)O vapor at relatively high-pressure, was investigated for a set of organic materials. While the ion signals are generally improved with increasing H(2)O pressure upon 12 keV Ga(+) bombardment, a specific enhancement of the protonated ion intensity is clearly demonstrated in each case. For instance, the presence of H(2)O vapor induces an enhancement by one order of magnitude of the [M + H](+) static SIMS intensity for the antioxidant Irgafos 168 and a ∼1.5-fold increase for polymers such as poly(vinyl pyrrolidone).

Analysis of fatty acid composition of <I>Ulva pertusa</I> Kjellm by gas chromatography/mass spectrometry

A method of gas chromatography/mass spectrometry (GC/MS) was established to determine the fatty acids of Ulva pertusa Kjellm. The total lipids of Ulva pertusa Kjellm were extracted using Folch method, derivatized with HCl-CH3OH solution, and analyzed by GC/MS. The fragmentation patterns and mass spectrometry characteristics of saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids were analyzed and concluded by regular patterns of organic mass spectrometry. According to the database index and standard controls, twenty-four fatty acid components in Ulva pertusa Kjellm were identified, and the contents of 9,12,15-octadecatrienoic acid, 4,7,10,13-hexadecatetraenoic acid and 6,9,2,15-octadecatetraenoic acid accounted for 45.14% of the total fatty acids. The qualitative results of fatty acids in Ulva pertusa Kjellm show that it is very useful in identifying fatty acid methyl esters by characteristic ions, especially polyunsaturated fatty acid methyl esters.

Organic Mass Spectrometry in Art and Archaeology

Organic Mass Spectrometry in Art and Archaeology

Organic mass spectrometry in art and archaeology

Organic mass spectrometry in art and archaeology

Characterization of aerosol plumes in nanosecond laser ablation of molecular solids at atmospheric pressure

Ablation of molecular solids with pulsed ultraviolet lasers at atmospheric pressure is an important process in (bio-)organic mass spectrometry. Of practical importance for analytical sampling and analysis are the plume formation and expansion. Plumes formed by atmospheric-pressure laser ablation of anthracene and 2,5-dihydroxybenzoic acid (2,5-DHB) were studied by light scattering imaging, which showed significant material release in the form of aerosols. The monitored plume expansion dynamics could be fitted to the drag-force model, yielding initial plume velocities of 150 m/s for anthracene and 43 m/s for DHB. While the angle of incidence does not affect the plume direction and propagation, a large dependence of the plume-expansion velocity on the laser pulse energy could be found, which is limited at atmospheric pressure by the onset of plasma shielding. With respect to analytical applications, the efficiency of sampling of the laser ablation products by a capillary could be experimentally visualized.

The micro-discharge family (dark, corona, and glow-discharge) for analytical applications realized by dielectric barriers

The similarity principles of electric plasmas, and the current-voltage characteristics of the most prominent kinds of discharges used for analytical applications, are discussed. Most of the discharges can be miniaturized, and some of the analytical applications of different discharges can be realized by use of dielectric barriers for analytical applications, for example element spectrometry, as an ionization source for ion-mobility spectrometry or organic mass spectrometry, and as an electrospray ionization source.

Low vacuum photo electron emitting thin films

AbstractImpact ionisation is a standard procedure to ionise gaseous or vaporisable substances in organic mass spectrometry. In this work, a “softer” ionisation is introduced which seems to be an alternative ion source for reducing collision between substance molecules and the hot internal walls of the box. Through collision mainly found in impact ionisation sources, fragments are built especially from thermally sensitive substances falsifying the spectra. We present here photoelectron emitting materials for the soft ionisation using semiconducting compounds, galliumn nitride (GaN), and a representative of the borides, lanthanum hexaboride (LaB6). They are evaluated by photoelectron spectroscopic studies. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Sputtering of thin benzene films by large noble gas clusters

Molecular dynamics computer simulations have been employed to investigate the sputtering process of a benzene (C6H6) monolayer deposited on Ag{111} induced by an impact of slow clusters composed of large number of noble gas atoms. The sputtering yield, surface modifications, and the kinetic energy distributions of ejected species have been analyzed as a function of the cluster size and the binding energy of benzene to the Ag substrate. It is shown that high- and low-energy components can be identified in the kinetic energy distributions of ejected molecules. The mechanistic analysis of calculated trajectories reveals that high-energy molecules are emitted by direct interaction with projectile atoms that are backreflected from the metal substrate. Most of the molecules are ejected by this process. Low-energy molecules are predominantly emitted by a recovering action of the substrate deformed by the impact of a massive cluster. The increase of the binding energy leads to attenuation of both high- and low-energy ejection channels. However, low-energy ejection is particularly sensitive to the variation of this parameter. The area of the molecular overlayer sputtered by the projectile impact is large and increases with the cluster size and the kinetic energy of the projectile. Also the size and the shape of this area are sensitive to the changes of the binding energy. The radius of the sputtered region decreases, and its shape changes from almost circular to a ring-like zone when the binding energy is increased. Some predictions about the perspectives of the application of large clusters in the organic secondary ion mass spectrometry are discussed.

Organic mass spectrometry at the beginning of the 21st century

Mass spectrometry in the last 15–20 years has become one of the first methods of the qualitative analysis and quantitative determination of various substances, from isotopes of chemical elements to synthetic polymers, proteins, and nucleic acids. This method allows analysts to work with both individual compounds and most complex mixtures that contain hundreds and thousands of compounds. It is the best in terms of the sensitivity, information content, and rapidity. This review covers the present-day achievements of mass spectrometry, including ionization and ion separation methods and different versions of its application in various fields of science and human activity.

The application of ToF-SIMS to the analysis of herbicide formulation penetration into and through leaf cuticles

Understanding the movement of the active ingredient in relation to the other formulation components following application is crucial to an overall understanding of herbicide performance. We describe the novel use of time-of-flight secondary ion mass spectrometry (ToF-SIMS) as a tool for following the movement of herbicide formulation components into and across plant cuticles. This technique provides new insights since it provides both high (sub-micron) spatial resolution combined with the chemical specificity associated with organic mass spectrometry. The components studied include the oligomeric ethoxylate surfactants Synperonic A7 and A20 and active ingredient Sulfosate (trimesium glyphosate). The movement of these molecules, both separately and when combined in a simple formulation, into the surface of Prunus laurocerasus leaves and across the isolated plant cuticle was investigated and clear differences in penetration/diffusion behaviour were identified. ToF-SIMS was uniquely able to (simultaneously) spatially resolve all the species involved, including the anion and cation components of the active incredient. Also, using spectral reconstructions from the imaging raw data streams, the behaviour of individual oligomers within the surfactant distributions, could be assessed. The observations are discussed with reference to the action of surfactants identified in parallel micro-structural studies and the current understanding of herbicide uptake.

A fragment-free ionization technique for organic mass spectrometry with large Ar cluster ions

In this report, we propose to use the incidence of cluster ions that are much larger than molecular ions as a fragment-free ionization technique for organic secondary ion mass spectrometry. Secondary ions were measured for amino acid and peptide targets bombarded with 3, 8 and 13 keV large Ar cluster ions. The relative yields of the fragment ions decreased drastically with increasing incident cluster size. Fragment-free ionization of the molecule was accomplished when large cluster ions with optimized size and energy were incident on a biomolecular sample.

Computational view of surface based organic mass spectrometry

Surface based mass spectrometric approaches fill an important niche in the mass analysis portfolio of tools. The particular niche depends on both the underlying physics and chemistry of molecule ejection as well as experimental characteristics. In this article, we use molecular dynamics computer simulations to elucidate the fundamental processes giving rise to ejection of organic molecules in atomic and cluster secondary ion mass spectrometry (SIMS), massive cluster impact (MCI) mass spectrometry, and matrix-assisted laser desorption ionization (MALDI) mass spectrometry. This review is aimed at graduate students and experimental researchers.

Atmospheric Pressure Chemical Ionization Source. 1. Ionization of Compounds in the Gas Phase

A novel chemical ionization source for organic mass spectrometry is introduced. This new source uses a glow discharge in the flowing afterglow mode for the generation of excited species and ions. The direct-current gas discharge is operated in helium at atmospheric pressure; typical operating voltages and currents are around 500 V and 25 mA, respectively. The species generated by this atmospheric pressure glow discharge are mixed with ambient air to generate reagent ions (mostly ionized water clusters and NO+), which are then used for the ionization of gaseous organic compounds. A wide variety of substances, both polar and nonpolar, can be ionized. The resulting mass spectra generally show the parent molecular ion (M+ or MH+) with little or no fragmentation. Proton transfer from ionized water clusters has been identified as the main ionization pathway. However, the presence of radical molecular ions (M+) for some compounds indicates that other ionization mechanisms are also involved. The analytical capabilities of this source were evaluated with a time-of-flight mass spectrometer, and preliminary characterization shows very good stability, linearity, and sensitivity. Limits of detection in the single to tens of femtomole range are reported for selected compounds.

Commercial development of HR-ICPMS, MC-ICPMS and HR-GDMS

Even though mass spectrometry is deeply rooted in isotopic analysis (identification of the nuclides and the measurement of isotope ratios), the analytical achievements of mass spectrometers for structural analysis and compound identification have been of such extraordinary significance and utility that the practice of “organic mass spectrometry” has completely overshadowed inorganic applications (elemental and isotopic analysis). At recent annual meetings of the American Society of Mass Spectrometry (ASMS), originally founded by inorganic mass spectrometrists, sessions devoted to inorganic applications have been almost non-existent. However, the 17th James L. Waters Symposium, “Recognising Pioneers in the Development of Analytical Instrumentation”, gave testimony to a renaissance that is occurring in the practice of inorganic mass spectrometry.

新しい質量分析技術の法医学領域への応用

In the fields of legal medicine and forensic toxicology, numerous drugs and poisons obtained from diverse biological specimens such as whole blood, urine, and hair need to be identified and quantified. Therefore, it is necessary to develop new methods for analysis of drugs, especially mass spectrometric methods. In this paper, we introduce three methods—surface ionization organic mass spectrometry, a combination of mass spectrometry and cryogenic oven trapping (COT), and laser spray ionization (LSI)—and their application to legal medicine. Gas chromatography/surface ionization organic mass spectrometry is very sensitive in detecting drugs containing tertiary amine residues; for Phencyclidine (PCP), its sensitivity is 20 to 1,000 times higher than that of the conventional electron ionization method. Surface ionization organic mass spectrometry is suitable for compounds containing cyclic tertiary amino side chains. COT in combination with gas chromatography has enabled detection of many volatile organic compounds (VOCs) with high sensitivity. We have succeeded in quantifying several VOCs, such as chloroform, cyanide, thinner components, ethanol, and general anesthetics in whole blood by COT; COT affords a sensitivity that is 10 to 50 times higher than that of the conventional headspace gas chromatography method. Recently, we succeeded in identifying and quantifying 15 VOCs in human whole blood with the combination of COT and mass spectrometry. LSI is a new ionization method for liquid chromatography/mass spectrometry. We have succeeded in detecting aconitine alkaloids and psychopharmaceuticals using LSI. In the infusion mode, aconitine and haloperidol were ionized with higher efficiency compared to that in the conventional electrospray mode. However, since the signals in the LSI mode are not stable, it is necessary to improve the stability of signals in the LSI mode for applying LSI to forensic toxicology.

Isotopic labelling in mass spectrometry as a tool for studying reaction mechanisms of ion dissociations

AbstractPerhaps the greatest influence that isotopic labelling experiments have had on organic mass spectrometry is that reaction mechanisms originally borrowed from the chemistry of neutral counterparts have proved to be inadequate for explaining the results. It was therefore necessary to devise completely new types of fragmentation mechanisms and unconventional structures for organic gas‐phase cations. In most cases the labelling technique allows one to discover the positions at which the label atoms are found in both the charged and neutral products of an ion's dissociation. These experimental results are often difficult to rationalize by any simple mechanism, but they nearly always indicate how chemical computations should be directed in order for the latter to be able to provide a better mechanistic understanding. This short article describes some significant studies involving D and 18‐O labelling that well support the above assertions, using as examples the behaviour of some quite simple organic molecules. Copyright © 2007 John Wiley & Sons, Ltd.

Organic mass spectrometry with low-energy projectiles

Molecular dynamics computer simulations have been employed to elucidate mechanisms responsible for uplifting of a monolayer of benzene and polystyrene molecules adsorbed on Ag{1 1 1} by low-energy atomic and cluster Ar projectiles. The sputtering yield and mass distributions of ejected particles are analyzed depending on the type and the kinetic energy of a projectile. It is shown that the relative contribution of intact molecules can be greatly enhanced if the kinetic energy of atomic projectile is reduced below 60 eV. At these energies, however, the efficiency of desorption is low and the ejection process is limited only to loosely bound molecules. Much better results can be obtained for cluster projectiles containing hundreds of Ar atoms with the incident energy of a few eV per atom. The impact of such particles leads to a gentle and very efficient removal of intact organic molecules originally adsorbed at the surface.

Guideline for the diagnosis and management of glutaryl‐CoA dehydrogenase deficiency (glutaric aciduria type I)

Glutaryl-CoA dehydrogenase (GCDH) deficiency is an autosomal recessive disease with an estimated overall prevalence of 1 in 100 000 newborns. Biochemically, the disease is characterized by accumulation of glutaric acid, 3-hydroxyglutaric acid, glutaconic acid, and glutarylcarnitine, which can be detected by gas chromatography-mass spectrometry of organic acids or tandem mass spectrometry of acylcarnitines. Clinically, the disease course is usually determined by acute encephalopathic crises precipitated by infectious diseases, immunizations, and surgery during infancy or childhood. The characteristic neurological sequel is acute striatal injury and, subsequently, dystonia. During the last three decades attempts have been made to establish and optimize therapy for GCDH deficiency. Maintenance treatment consisting of a diet combined with oral supplementation of L: -carnitine, and an intensified emergency treatment during acute episodes of intercurrent illness have been applied to the majority of patients. This treatment strategy has significantly reduced the frequency of acute encephalopathic crises in early-diagnosed patients. Therefore, GCDH deficiency is now considered to be a treatable condition. However, significant differences exist in the diagnostic procedure and management of affected patients so that there is a wide variation of the outcome, in particular of pre-symptomatically diagnosed patients. At this time of rapid expansion of neonatal screening for GCDH deficiency, the major aim of this guideline is to re-assess the common practice and to formulate recommendations for diagnosis and management of GCDH deficiency based on the best available evidence.

Measurements of secondary ions emitted from organic compounds bombarded with large gas cluster ions

We propose to use cluster ions that are much larger than the molecular ions as primary ions for organic secondary ion mass spectrometry. Incident Ar cluster ion beams with energies from 10 to 20keV and a mean size of about 1000 atoms/cluster were used. Secondary ions were measured for a thin arginine film target (200nm) bombarded with large Ar cluster ions using a time-of-flight technique. Molecular ions of arginine and characteristic fragment ions were detected with high sensitivity. When large Ar cluster ions such as Ar1500 were incident on the arginine target, molecular ions of arginine were detected with little fragment ions. This indicates that large cluster ions can ionize arginine molecules without damaging them.