Prof. Dr. Dietrich Volmer
Profil
Forschungsthemen5
Einsatz der akustischen Levitation zur Etablierung einer vollständig integrierten "Lab-in-a- Droplet"-Plattform: Kombination von in stillo Probenvorbereitung und direkter massenspektrometrischer Analyse
Quelle ↗Förderer: DFG Sachbeihilfe Zeitraum: 02/2026 - 01/2029 Projektleitung: Prof. Dr. Dietrich Volmer
Ein systemischer Ansatz zur Charakterisierung von Vitamin D: Ausdehnung der massenspektrometrischen Analytik auf Gewebe, als Ergänzung zu Serum-Vitamin D
Quelle ↗Förderer: DFG Sachbeihilfe Zeitraum: 06/2026 - 05/2029 Projektleitung: Prof. Dr. Dietrich Volmer, Dr. Dr. Caroline Stokes, Prof. Dr. Caroline Sarah Stokes
Multimodale klinische Massenspektrometrie für die Untersuchung von Therapieresistenz - MSTARS
Quelle ↗Förderer: Bundesministerium für Forschung, Technologie und Raumfahrt Zeitraum: 03/2020 - 02/2023 Projektleitung: Prof. Dr. Dietrich Volmer
Neuartige analytische Ansätze für die Quantifizierung niedrigabundanter, dynamischer Metaboliten des Vitamin-D-Stoffwechsels
Quelle ↗Förderer: DFG Sachbeihilfe Zeitraum: 01/2020 - 02/2024 Projektleitung: Prof. Dr. Dietrich Volmer
Neuartige massenspektrometrische Verfahren für die Lignomforschung und Quantifizierung von Lignin
Quelle ↗Förderer: DFG Sachbeihilfe Zeitraum: 07/2020 - 09/2024 Projektleitung: Prof. Dr. Dietrich Volmer
Mögliche Industrie-Partner10
Stand: 26.4.2026, 19:48:44 (Top-K=20, Min-Cosine=0.4)
- 25 Treffer56.0%
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- EU: Printed Logic for Applications of Screen Matrix Activation (PLASMAS)
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- EU: Printed Logic for Applications of Screen Matrix Activation (PLASMAS)P56.0%
- EU: Printed Logic for Applications of Screen Matrix Activation (PLASMAS)
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- EU: Printed Logic for Applications of Screen Matrix Activation (PLASMAS)P56.0%
- EU: Printed Logic for Applications of Screen Matrix Activation (PLASMAS)
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- EU: Printed Logic for Applications of Screen Matrix Activation (PLASMAS)P56.0%
- EU: Printed Logic for Applications of Screen Matrix Activation (PLASMAS)
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- Gezielte Salix-Züchtung und Analyse des chemischen Profils für den Einsatz von Weidenrinde in der PharmazieP55.9%
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- 64 Treffer55.4%
- Entwicklung von wenig löslichen, homodispers nanoskopischen Metallfluoriden in Zahnzementen, Kompositfüllmaterialien und in Prophylaxepräparaten zum Einsatz im DentalbereichP55.4%
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- 97 Treffer55.2%
- Surface-enhanced Raman spectroscopy in liquid biopsy for breast cancerP55.2%
- Surface-enhanced Raman spectroscopy in liquid biopsy for breast cancer
- 97 Treffer55.2%
- Surface-enhanced Raman spectroscopy in liquid biopsy for breast cancerP55.2%
- Surface-enhanced Raman spectroscopy in liquid biopsy for breast cancer
- 57 Treffer54.7%
- Interfaces in opto-electronic thin film multilayer devicesP54.7%
- Interfaces in opto-electronic thin film multilayer devices
Publikationen25
Top 25 nach Zitationen — Quelle: OpenAlex (BAAI/bge-m3 embedded für Matching).
Journal of Mass Spectrometry · 509 Zitationen · DOI
This tutorial presents the most common ion activation techniques employed in tandem mass spectrometry. In-source fragmentation and metastable ion decompositions, as well as the general theory of unimolecular dissociations of ions, are initially discussed. This is followed by tandem mass spectrometry, which implies that the activation of ions is distinct from the ionization step, and that the precursor and product ions are both characterized independently by their mass/charge ratios. In collision-induced dissociation (CID), activation of the selected ions occurs by collision(s) with neutral gas molecules in a collision cell. This experiment can be done at high (keV) collision energies, using tandem sector and time-of-flight instruments, or at low (eV range) energies, in tandem quadrupole and ion trapping instruments. It can be performed using either single or multiple collisions with a selected gas and each of these factors influences the distribution of internal energy that the activated ion will possess. While CID remains the most common ion activation technique employed in analytical laboratories today, several new methods have become increasingly useful for specific applications. More recent techniques are examined and their differences, advantages and disadvantages are described in comparison with CID. Collisional activation upon impact of precursor ions on solid surfaces, surface-induced dissociation (SID), is gaining importance as an alternative to gas targets and has been implemented in several different types of mass spectrometers. Furthermore, unique fragmentation mechanisms of multiply-charged species can be studied by electron-capture dissociation (ECD). The ECD technique has been recognized as an efficient means to study non-covalent interactions and to gain sequence information in proteomics applications. Trapping instruments, such as quadrupole ion traps and Fourier transform ion cyclotron resonance instruments, are particularly useful for the photoactivation of ions, specifically for fragmentation of precursor ions by infrared multiphoton dissociation (IRMPD). IRMPD is a non-selective activation method and usually yields rich fragmentation spectra. Lastly, blackbody infrared radiative dissociation is presented with a focus on determining activation energies and other important parameters for the characterization of fragmentation pathways. The individual methods are presented so as to facilitate the understanding of each mechanism of activation and their particular advantages and representative applications.
The Analyst · 264 Zitationen · DOI
Liquid chromatography-mass spectrometry analysis of small molecules from biofluids requires sensitive and robust assays. Because of the very complex nature of many biological samples, efficient sample preparation protocols to remove unwanted components and to selectively extract the compounds of interest are an essential part of almost every bioanalytical workflow. This review describes the most common problems encountered during sample preparation, ways to optimize established sample preparation techniques and important recent developments to reduce or eliminate major interferents from biofluids.
The Analyst · 211 Zitationen · DOI
Mass spectrometry imaging (MSI) has proven to be extremely useful for applications such as the spatial analysis of peptides and proteins in biological tissue, the performance assessment of drugs in vivo or the measurement of protein or metabolite expression as tissue classifiers or biomarkers from disease versus control tissue comparisons. The most popular MSI technique is MALDI mass spectrometry. First invented by Richard Caprioli in the mid-1990s, it is the highest performing MSI technique in terms of spatial resolution, sensitivity for intact biomolecules and application range today. The unique ability to identify and spatially resolve numerous compounds simultaneously, based on m/z values has inter alia been applied to untargeted and targeted chemical mapping of biological compartments, revealing changes of physiological states, disease pathologies and metabolic faith and distribution of xenobiotics. Many MSI applications focus on lipid species because of the lipids' diverse roles as structural components of cell membranes, their function in the surfactant cycle, and their involvement as second messengers in signalling cascades of tissues and cells. This article gives a comprehensive overview of lipid imaging techniques and applications using established MALDI and SIMS methods but also other promising MSI techniques such as DESI.
Liver International · 193 Zitationen · DOI
Herein, we focus on the epidemiological and functional relationships between vitamin D deficiency and CLD, followed by a discussion of the potential implications for therapeutic interventions.
NPARC · 183 Zitationen
Ion suppression is one form of matrix effect that liquid chromatography–mass spectrometry (LC–MS) techniques suffer from, regardless of the sensitivity or selectivity of the mass analyzer used. Ion suppression negatively affects several analytical figures of merit, such as detection capability, precision, and accuracy. The limited knowledge of the origin and mechanism of ion suppression makes this problem difficult to solve in many cases. Over the past decade and a half since the response-reducing phenomenon was exposed, however, protocols have been developed not only to test for its presence but also to account for its effects and eliminate the risk of ion suppression altogether. Because there is no universal solution for the matrix effect, some of the viable options are discussed briefly in this tutorial, which alone or in combination can help regain the quality of LC–MS analysis for the particular matrix–analyte combination. Two commonly used techniques to detect the presence of the matrix effect are illustrated. Modifying instrumental components and parameters, chromatographic separation, and sample preparation are all considered as means of reducing or possibly eliminating ion suppression. A variety of calibration techniques for compensating the effects of the phenomenon also are discussed.
Carbon Research · 166 Zitationen · DOI
Abstract Exploring the source, transformation pathways, and the fate of natural organic matter (NOM) is critical to understanding the regional/global carbon cycle and carbon budget. The dissolved fraction of NOM, i.e., dissolved organic matter (DOM), is a complex mixture resulting from the transformation of plant, animal and microbial matter and plays a crucial role in many biogeochemical processes at the land-ocean-atmosphere interfaces. The advance of Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) makes the detailed characterization of DOM at the molecular level possible. On the other hand, elucidation of complex DOM sample also presents significant analytical challenges, and these challenges also act as a driving force for the instrumentation and methodology development on FT-ICR MS. This review article has been written to aid those working in biogeochemistry, environmental and atmospheric chemistry, and related areas which investigate elemental cycles and DOM transformations. First, the fundamental theory, historical perspective, and recent advances in the field have been introduced. The detailed molecular characterization of environmental and geological samples continues to present significant analytical challenges, and it also has become a driving force for the development of the instrumentation and experimental methods. These achievements in DOM analysis have had an impact upon the fields of environmental science, geochemistry, and analytical chemistry. Next, varieties of applications of FT-ICR MS have also been described, followed by our view of the future of this technique in earth science research. We believe that this review covers the essential pairing of FT-ICR MS and collectively offers environmental and geochemical scientists a substantial resource for their research. Graphical abstract
Rapid Communications in Mass Spectrometry · 165 Zitationen · DOI
‘Wrong-way-round’ electrospray ionization, in the present context, refers to observation of intense [M + H]+ ions electrosprayed from strongly basic solutions and of [M − H]− ions from strongly acidic solutions. Most previous investigations of this phenomenon have been directed at variations in charge-state distributions for polyfunctional peptides and proteins as a function of bulk solution pH. The present work extends that of Hiraoka et al. (J. Mass Spectrom. Soc. Japan 43, 127 (1995)) on the pH dependence of absolute mass spectral intensities of ions in electrospray mass spectra of amino acids. This choice of test analyte permits investigation of both positive- and negative-ion mass spectra without potential complications from changes in secondary and tertiary structures as the pH is varied. The intensities of [M + H]+ and [M − H]− ions, over the pH range 3 to 11, varied by factors of 3–5 despite calculated variations of several orders of magnitude in equilibrium concentrations in the bulk solution. The same behaviour was observed for derivatized amino acids such as amides and methyl esters. Measurements of pH of collected spray, and of the total current carried by the charged droplets, confirmed that these observations can not be accounted for in terms of wholesale pH switching from acidic to basic or vice versa by electrochemical reactions at the electrospray needle. Precursors of the ‘wrong-way-round’ ions were sought by conventional precursor-ion scanning experiments but with minimal declustering conditions in the atmospheric-pressure ion-source interface. In the case of added electrolytes, such as ammonia and acetic acid, which are both volatile and capable of Brønsted acid–base behaviour, the observations were consistent with earlier interpretations involving e.g. [M + NH4+] precursors for [M + H]+ ions. Such explanations were not applicable to similar observations made for solutions with added tetramethylammonium hydroxide or hydrochloric acid. © 1997 Crown Copyright, Canada
Analytical and Bioanalytical Chemistry · 159 Zitationen · DOI
Vitamin D is an important determinant of bone health at all ages. The plasma concentrations of 25-hydroxy vitamin D (25-OH D) and other metabolites are used as biomarkers for vitamin sufficiency and function. To allow for the simultaneous determination of five vitamin D metabolites, 25-OH D(3), 25-OH D(2), 24,25-(OH)(2) D(3), 1,25-(OH)(2) D(3), and 1,25-(OH)(2) D(2), in low volumes of human plasma, an assay using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was established. Plasma samples were spiked with isotope-labeled internal standards and pretreated using protein precipitation, solid-phase extraction (SPE) and a Diels-Alder derivatization step with 4-phenyl-1,2,4-triazoline-3,5-dione. The SPE recovery rates ranged from 55% to 85%, depending on the vitamin D metabolite; the total sample run time was <5 min. Mass spectrometry was conducted using positive ion electrospray ionization in the multiple reaction monitoring mode on a quadrupole-quadrupole-linear ion trap instrument after pre-column addition of methylamine to increase the ionization efficiency. The intra- and inter-day relative standard deviations were 1.6-4.1% and 3.7-6.8%, respectively. The limit of quantitation for these compounds was determined to be between 10 and 20 pg/mL. The 25-OH D results were compared with values obtained for reference materials (DEQAS). In addition, plasma samples were analyzed with two additional Diasorin antibody assays. All comparisons with conventional methods showed excellent correlations (r(2) = 0.9738) for DEQAS samples, demonstrating the high degree of comparability of the new UHPLC-MS/MS technique to existing methods.
Analytical Chemistry · 159 Zitationen · DOI
Simultaneous detection and confirmation of 15 quinolone antibiotics was accomplished by fast short-column liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC/MS/MS). Several physiochemical parameters such as hydrophobicity and aqueous dissociation constants were calculated from the structural formulas of the quinolone drugs, and their impact on both chromatographic and mass spectrometric behavior was studied. Additionally, a possible influence of bulk solution pH on electrospray detection sensitivity of 4-quinolones was investigated and compared to predictions based on solution-phase equilibria. A signal intensity comparison of the MH+ ions at different pH values for all 15 compounds did not reveal any pH effect, despite variations by several orders of magnitude in equilibrium concentrations in bulk solution. To demonstrate the potential of the LC/MS/MS method, its application to trace analysis in several biological matrices such as milk, salmon, and human urine was investigated. The method was shown to be sensitive with detection limits down to 1 ppb in both milk and salmon tissue. The versatility of the method was also exhibited by utilizing it for rapid identification of urinary metabolites of ciprofloxacin. Finally, a new complementary approach is described for confirmatory analyses of 4-quinolones by means of a quasi-MS/MS/MS technique involving in-source collision-induced dissociation. It is shown that LC/quasi-MS/MS/MS can significantly enhance structural information and, thus, the specificity of analysis for the investigated 4-quinolones.
Mass Spectrometry Reviews · 143 Zitationen · DOI
Vitamin D compounds belong to a group of secosteroids, which occur naturally as vitamin D3 in mammals and D2 in plants. Vitamin D is vital for bone health but recent studies have shown a much wider role in the pathologies of diseases such as diabetes, cancer, autoimmune, neurodegenerative, mental and cardiovascular diseases. Photosynthesis of vitamin D in the human skin and subsequent hepatic and renal metabolism generate a wide range of transformation products occurring over a large dynamic range spanning from picomolar to nanomolar levels. This necessitates selective and sensitive analytical methods to quantitatively capture these low concentration levels in relevant tissues such as blood. Ideally, vitamin D assessment would be performed using a universal and standardized analytical method available to clinical laboratories that provides reliable and accurate quantitative results for all relevant vitamin D metabolites with sufficiently high throughput. At present, LC-MS/MS assays are the most promising techniques for vitamin D analysis. The present review focuses on developments in mass spectrometry methodologies of the past 12 years. It will highlight detrimental influences of the biological matrix, epimer contributions, pitfalls of specific mass spectrometry data acquisition routines (in particular multiple reaction monitoring, MRM), influence of ionization source, derivatization reactions, inter-laboratory comparisons on precision, accuracy, and application range of vitamin D metabolites.
Drug Metabolism and Disposition · 135 Zitationen · DOI
Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics · 133 Zitationen · DOI
Physical Chemistry Chemical Physics · 133 Zitationen · DOI
Lignin is a component of lignocellulosic biomass and a promising matrix for recovering important renewable aromatic compounds. We present a new approach of electro-oxidative cleavage of lignin, dissolved in a special protic ionic liquid, using an anode with particular electro-catalytic activity. As appropriate ionic liquid triethylammonium methanesulfonate was identified, synthesised, explored for dissolution of alkali-lignin and used for electrolysis of 5 wt.% lignin solutions. As appropriate anode material, oxidation-stable ruthenium-vanadium-titanium mixed oxide electrodes were prepared and explored for their electro-catalytic activity. The electrolysis was performed at several potentials in the range from 1.0 V to 1.5 V (vs. an Ag pseudo reference electrode). A wide range of aromatic fragments was identified as cleavage products by means of GC-MS and HPLC measurements.
Neurobiology of Disease · 116 Zitationen · DOI
Post-translational modification of small GTPases by farnesyl- (FPP) and geranylgeranylpyrophosphate (GGPP) has generated much attention due to their potential contribution to cancer, cardiovascular and neurodegenerative diseases. Prenylated proteins have been identified in numerous cell functions and elevated levels of FPP and GGPP have been previously proposed to occur in Alzheimer disease (AD) but have never been quantified. In the present study, we determined if the mevalonate derived compounds FPP and GGPP are increased in brain grey and white matter of male AD patients as compared with control samples. This study demonstrates for the first time that FPP and GGPP levels are significantly elevated in human AD grey and white matter but not cholesterol, indicating a potentially disease-specific targeting of isoprenoid regulation independent of HMG-CoA-reductase. Further suggesting a selective disruption of FPP and GGPP homeostasis in AD, we show that inhibition of HMG-CoA reductase in vivo significantly reduced FPP, GGPP and cholesterol abundance in mice with the largest effect on the isoprenoids. A tentative conclusion is that if indeed regulation of FPP and GGPP is altered in AD brain such changes may stimulate protein prenylation and contribute to AD neuropathophysiology.
Rapid Communications in Mass Spectrometry · 114 Zitationen · DOI
In this work, a high repetition rate laser matrix-assisted laser desorption/ionization (MALDI) source is studied on a quadrupole-time-of-flight (QqTOF) and a triple quadrupole (QqQ) mass spectrometer for rapid quantification of small pharmaceutical drugs. The high repetition rate laser allows an up to 100-fold higher pulse frequency as compared with regular MALDI lasers, resulting in much larger sample throughput and number of accumulated spectra. This increases the reproducibility of signal intensities considerably, with average values being around 5% relative standard deviation after taking into account the area ratio of the analyte to an internal standard. Experiments were conducted in MS/MS mode to circumvent the large chemical background due to MALDI matrix ions in the low mass range. The dynamic range of calibration curves on the QqTOF mass spectrometer extended over at least two orders of magnitude, whereas on the QqQ it extended over at least three orders of magnitude. Detection limits ranged from 60-400 pg/microL on the QqTOF and from 6-70 pg/microL on the QqQ for a series of benzodiazepines. The benzodiazepine content of commercial pill formulations was quantified, and less than 5% error was obtained between the present method and the manufacturer's certified values. Furthermore, a high sample throughput was achieved with this method, so that a single MALDI spot could be quantitatively scanned in as little as 15 s, and an entire 96-well MALDI plate in 24 min.
Analytical and Bioanalytical Chemistry · 108 Zitationen · DOI
The current developments in metabolomics and metabolic profiling technologies have led to the discovery of several new metabolic biomarkers. Finding metabolites present in significantly different levels between sample sets, however, does not necessarily make these metabolites useful biomarkers. The route to valid and applicable biomarkers (biomarker qualification) is long and demands a significant amount of work. In this overview, we critically discuss the current state-of-the-art of metabolic biomarker discovery, with highlights and shortcomings, and suggest a pathway to clinical usefulness.
Rapid Communications in Mass Spectrometry · 105 Zitationen · DOI
Solid-phase microextraction combined with fast short-column liquid chromatography/mass spectrometry (SPME/LC/MS) was used for isolating and analysing 11 corticosteroids and 2 steroid conjugates from urine samples. Several SPME parameters such as polarity of fibres, extraction time and effect of ionic strength, were investigated, and their impact on the SPME/LC/MS technique was studied. To demonstrate the potential of the SPME/LC/MS method, its application to the determination of steroids in human urine was investigated. The method was shown to be sensitive with detection limits between 4 and 30 ng/mL and precision between 4.9 and 11.1% RSD through the use of an internal standard technique. The versatility of the method was also exhibited by its excellent linearity in the concentration range of 20 to 20,000 ng/mL in urine for all investigated compounds. A comparison of the SPME/LC/MS method with LC/MS methods utilizing traditional sample preparation techniques, shows that the former offers similar performance in terms of precision, linearity and detection limits, but is clearly easier to use and faster to perform.
Rapid Communications in Mass Spectrometry · 103 Zitationen · DOI
The purpose of the present paper was to study some of the underlying physical and technical aspects of high-throughput quantitative matrix-assisted laser desorption/ionization (MALDI) of small drug molecules. A prototype MALDI-triple quadrupole instrument equipped with a high repetition rate laser was employed. Initially, the detection limits and dynamic ranges for the quantitation of four drugs (quinidine, danofloxacin, ramipril and nadolol) were determined. Internal standards were carefully chosen for each of these analytes in terms of structure similarity and fragmentation pathways. Three organic matrices were tested for these assays, resulting in different crystallization behaviors and measurement reproducibilities. alpha-Cyano-4-hydroxycinnamic acid yielded the best results and was subsequently employed for the quantitative determination of all four analytes. Further experiments considered the role of laser energy and pulse rate on the ablated areas as well as ion signals. Light microscope and scanning electron microscope images allowed the examination of the ablated area of the MALDI spots. The images showed convincing evidence that the ablated area was virtually void of crystals after analysis, with no preferential removal of material in the center of the laser's path. Average values for the amount of material ablated were determined to be 3.9+/-0.5% of the total spot size, and as low as 19.5 attomoles of analyte were detectable for our most sensitive analyte, ramipril. It was calculated that, under these assay conditions, it was possible to accurately quantify less than 1 femtomole of all analytes with the use of appropriately pure internal standards. These studies showed very promising results for the quantitative nature of MALDI for small molecules with molecular weights less than 500 Da.
Scientific Reports · 98 Zitationen · DOI
Lignin's aromatic building blocks provide a chemical resource that is, in theory, ideal for substitution of aromatic petrochemicals. Moreover, degradation and valorization of lignin has the potential to generate many high-value chemicals for technical applications. In this study, electrochemical degradation of alkali and Organosolv lignin was performed using the ionic liquids 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and triethylammonium methanesulfonate. The extensive degradation of the investigated lignins with simultaneous almost full recovery of the electrolyte materials provided a sustainable alternative to more common lignin degradation processes. We demonstrate here that both the presence (and the absence) of water during electrolysis and proton transport reactions had significant impact on the degradation efficiency. Hydrogen peroxide radical formation promoted certain electrochemical mechanisms in electrolyte systems "contaminated" with water and increased yields of low molecular weight products significantly. The proposed mechanisms were tentatively confirmed by determining product distributions using a combination of liquid chromatography-mass spectrometry and gas-chromatography-mass spectrometry, allowing measurement of both polar versus non-polar as well as volatile versus non-volatile components in the mixtures.
Mass Spectrometry Reviews · 93 Zitationen · DOI
Abstract Lignin is currently one of the most promising biologically derived resources, due to its abundance and application in biofuels, materials and conversion to value aromatic chemicals. The need to better characterize and understand this complex biopolymer has led to the development of many different analytical approaches, several of which involve mass spectrometry and subsequent data analysis. This review surveys the most important analytical methods for lignin involving mass spectrometry, first looking at methods involving gas chromatography, liquid chromatography and then continuing with more contemporary methods such as matrix assisted laser desorption ionization and time‐of‐flight‐secondary ion mass spectrometry. Following that will be techniques that directly ionize lignin mixtures—without chromatographic separation—using softer atmospheric ionization techniques that leave the lignin oligomers intact. Finally, ultra‐high resolution mass analyzers such as FT‐ICR have enabled lignin analysis without major sample preparation and chromatography steps. Concurrent with an increase in the resolution of mass spectrometers, there have been a wealth of complementary data analyses and visualization methods that have allowed researchers to probe deeper into the “lignome” than ever before. These approaches extract trends such as compound series and even important analytical information about lignin substructures without performing lignin degradation either chemically or during MS analysis. These innovative methods are paving the way for a more comprehensive understanding of this important biopolymer, as we seek more sustainable solutions for our human species’ energy and materials needs.
Analytical Chemistry · 90 Zitationen · DOI
In the present work we describe the development of an analytical technique for simultaneous profiling of over 100 biochemically related lipid mediators in biological samples. A multistep procedure was implemented to extract eicosanoids and other bioactive lipids from the biological matrix, chromatographically separate them using fast reversed-phase liquid chromatography, tentatively identify new candidate eicosanoids through a matching process of retention times, isotope distribution patterns, and high-resolution orbitrap MS/MS fragmentation patterns, and subsequently quantify tentative candidates by means of analytical reference standards. Key new aspects of this profiling technique included the classification of bioactive lipids into 12 groups according to their calculated exact masses and the development of optimized liquid chromatographic conditions for these groups to achieve sufficient separation of the numerous isobaric and isomeric species, many of which exhibited virtually identical collision-induced dissociation behavior. Importantly, no analytical standards were required at this screening stage of the assay, and tentative identifications were achieved by matching results to selected reference species from each of the groups. The analytical figures of merit for the orbitrap assay such as linear dynamic range, limit of detection, limit of quantitation, and precision demonstrated that the performance of the assay was very similar to that of a quadrupole linear ion trap assay, which was used for validation purposes. The method allowed us to examine eicosanoid profiles within the signaling cascade in chronic lymphocytic leukemia (CLL) cells under basal conditions and following arachidonic acid stimulation. The preliminary screening based on high-resolution tandem mass spectrometry data along with isotope pattern and retention time matching revealed the presence of 15 bioactive lipids, belonging to a range of prostaglandin, leukotriene, and hydroxy and epoxy fatty acid lipid mediators produced by CLL cells.
Rapid Communications in Mass Spectrometry · 89 Zitationen · DOI
Most analytical methods in metabolomics are based on one of two strategies. The first strategy is aimed at specifically analysing a limited number of known metabolites or compound classes. Alternatively, an unbiased approach can be used for profiling as many features as possible in a given metabolome without prior knowledge of the identity of these features. Using high-resolution mass spectrometry with instruments capable of measuring m/z ratios with sufficiently low mass measurement uncertainties and simultaneous high scan speeds, it is possible to combine these two strategies, allowing unbiased profiling of biological samples and targeted analysis of specific compounds at the same time without compromises. Such high mass accuracy and mass resolving power reduces the number of candidate metabolites occupying the same retention time and m/z ratio space to a minimum. In this study, we demonstrate how targeted analysis of phospholipids as well as unbiased profiling is achievable using a benchtop orbitrap instrument after high-speed reversed-phase chromatography. The ability to apply both strategies in one experiment is an important step forward in comprehensive analysis of the metabolome.
The Analyst · 88 Zitationen · DOI
Analytical applications often require rapid measurement of compounds from complex sample mixtures. High-speed mass spectrometry approaches frequently utilize techniques based on direct ionization of the sample by laser irradiation, mostly by means of matrix-assisted laser desorption/ionization (MALDI). Compounds of low molecular weight are difficult to analyze by MALDI, however, because of severe interferences in the low m/z range from the organic matrix used for desorption/ionization. In recent years, surface-assisted laser desorption/ionization (SALDI) techniques have shown promise for small molecule analysis, due to the unique properties of nanostructured surfaces, in particular, the lack of a chemical background in the low m/z range and enhanced production of analyte ions by SALDI. This short review article presents a summary of the most promising recent developments in SALDI materials for MS analysis of low molecular weight analytes, with emphasis on nanostructured materials based on metals and semiconductors.
Journal of Chromatography A · 88 Zitationen · DOI
Rapid Communications in Mass Spectrometry · 79 Zitationen · DOI
A series of polyether ionophores (lasalocid, monensin-A, narasin-A and salinomycin) was investigated by electrospray ionization (ESI) tandem mass spectrometry (MS/MS). A fast short-column liquid chromatographic (LC) method, using a ternary gradient sequence, was developed to separate the ionophores in less than 4 minutes. Several mobile phase parameters such as pH and solvent additives were investigated, and their impact on both chromatographic and mass spectrometric behavior was studied. The ionophores readily formed stable complexes with various metal cations present as impurities in the solvents. Therefore, a method was developed to convert the ionophores into only sodium adduct species prior to ESI analysis. This procedure maximized both sensitivity and specificity in the subsequent MS/MS step. Low energy collision-induced dissociation (CID) of the sodium adduct ions resulted in a number of structure-diagnostic product ions for all ionophores. The proposed interpretation of these fragment ions is presented in this work. Additionally, the fragmentation of a series of monovalent carboxylic alkali-metal ion complexes of lasalocid was investigated under CID conditions. A comparison of the CID spectra revealed a decreasing degree of fragmentation in the order [M + H]+ approximately [M + NH4]+ > [M + Li]+ > [M-H + 2Li]+ > [M + Na]+ >> [M + Cs]+. To demonstrate the analytical potential of the LC/MS/MS method, its application to the determination of salinomycin in catfood samples was investigated. Salinomycin was recovered from catfood by a microwave solvent extraction procedure, and subsequently analyzed using LC/MS/MS of the sodium adduct ions.
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- Prof. Dr. Dietrich Volmer
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- Prof. Dr.
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- Mathematisch-Naturwissenschaftliche Fakultät
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- Institut für Chemie
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- Angewandte Analytik und Umweltchemie
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