13 results on '"Dietrich A, Volmer"'
Search Results
2. Laser Ablation Secondary Electrospray Ionization for In Situ Mass Spectrometric Interrogation of Acoustically-Levitated Droplets
- Author
-
Sebastian van Wasen, Yi You, Sebastian Beck, Jens Riedel, and Dietrich A. Volmer
- Subjects
Spectrometry, Mass, Electrospray Ionization ,Lasers ,Laser Therapy ,Peptides ,Mass Spectrometry ,Analytical Chemistry - Abstract
The composition of acoustically levitated droplets was probed by a novel combination of mid-IR laser evaporation and subsequent postionization via secondary electrospray ionization. The combination of microliter samples and subnanoliter sampling provided time-resolved interrogation of droplets and allowed for a kinetic investigation of the laser-induced release of the analyte, which was found to strongly depend on the analytes. The observed substance-specific delayed release of the analytes permitted baseline-separated discrimination of the analytes, ideal for the study of complex samples. The additionally applied postionization scheme was found to enable efficient detection of small volatile compounds as well as peptides. The detection of small molecules and peptides occurred under very different sampling geometries, pointing to two distinct underlying ionization mechanisms. Overall, our results suggest that the experimental setup presented in this study can serve as a widely applicable platform to study chemical reactions in acoustically levitated droplets as model reactors.
- Published
- 2022
3. Quantitative Analysis of Pharmaceutical Drugs Using a Combination of Acoustic Levitation and High Resolution Mass Spectrometry
- Author
-
Jens Riedel, Dietrich A. Volmer, Sebastian van Wasen, Sebastian Beck, and Yi You
- Subjects
Atmospheric pressure ,Chemistry ,010401 analytical chemistry ,Far-infrared laser ,Analytical chemistry ,Water ,Atmospheric-pressure chemical ionization ,Acoustics ,010402 general chemistry ,Mass spectrometry ,Acoustic levitation ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,Physics::Fluid Dynamics ,Matrix (chemical analysis) ,Matrix-assisted laser desorption/ionization ,Atmospheric Pressure ,Pharmaceutical Preparations ,Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ,Ionization - Abstract
A combination of acoustic levitation, laser vaporization, and atmospheric pressure chemical ionization mass spectrometry (APCI-MS) is presented in this study that enabled sensitive analysis of pharmaceutical drugs from an aqueous sample matrix. An unfocused pulsed infrared laser provided contactless sample desorption from the droplets trapped inside an acoustic levitator by activation of the OH stretching band of aqueous and alcoholic solvents. Subsequent atmospheric pressure chemical ionization was used between the levitated droplet and the mass spectrometer for postionization. In this setup, the unfocused laser gently desorbed the analytes by applying very mild repulsive forces. Detailed plume formation studies by temporally resolved schlieren experiments were used to characterize the liquid gas transition in this process. In addition, the role of different additives and solvent composition was examined during the ionization process. The analytical application of the technique and the proof-of-concept for quantitative analysis were demonstrated by the determination of selected pharmaceutical drugs in aqueous matrix with limits of quantification at the lower nanomolar level and a linear dynamic range of 3-4 orders of magnitude.
- Published
- 2021
- Full Text
- View/download PDF
4. Determination of Urinary Metabolites of the Emerging UV Filter Octocrylene by Online-SPE-LC-MS/MS
- Author
-
Heiko Hayen, Thomas Brüning, Daniel Bury, Vladimir N. Belov, Dietrich A. Volmer, Yulin Qi, and Holger M. Koch
- Subjects
Analyte ,Population ,UV filter ,Pilot Projects ,Urine ,010501 environmental sciences ,Mass spectrometry ,01 natural sciences ,Analytical Chemistry ,chemistry.chemical_compound ,Glucuronides ,Tandem Mass Spectrometry ,Nitriles ,Biomonitoring ,Humans ,education ,Glucuronidase ,0105 earth and related environmental sciences ,education.field_of_study ,Chromatography ,Escherichia coli K12 ,Chemistry ,010401 analytical chemistry ,0104 chemical sciences ,Octocrylene ,Acrylates ,Sample collection ,Sunscreening Agents ,Biomarkers ,Chromatography, Liquid - Abstract
Octocrylene (OC) is an emerging UV filter, which is used in the majority of sunscreens as well as other personal care products (PCP) and consumer products. Its presence in various environmental matrices has been reported. However, information on the internal OC exposure in humans is not available, due to the lack of appropriate biomarkers of exposure and analytical methods. Here, we describe a rugged, precise, and accurate analytical method for the determination of three OC metabolites (ester hydrolysis and alkyl chain oxidation products) in human urine by stable isotope dilution analysis. Urine samples are incubated with β-glucuronidase (E. coli K12) and then analyzed by liquid chromatography-electrospray ionization-triple quadrupole-tandem mass spectrometry with online turbulent flow chromatography for sample cleanup and analyte enrichment (online-SPE-LC-MS/MS). Syntheses of analytical standards, including deuterium-labeled internal standards, are also described. In a pilot study, we investigated the applicability of the metabolites as biomarkers of exposure in urine samples from the general population (n = 35). OC metabolites were detected in 91% of the samples, with the highest concentrations for three individuals having used sunscreen within 5 days prior to sample collection. We will apply the method in future human biomonitoring studies for OC exposure and risk assessment.
- Published
- 2017
- Full Text
- View/download PDF
5. Enhanced Mass Defect Filtering To Simplify and Classify Complex Mixtures of Lignin Degradation Products
- Author
-
Rolf Hempelmann, Dietrich A. Volmer, Verlaine Fossog, Tobias Dier, and Kerstin Egele
- Subjects
Atmospheric pressure ,Kendrick mass ,010401 analytical chemistry ,Molecular Conformation ,Analytical chemistry ,Electrochemical Techniques ,02 engineering and technology ,Photoionization ,021001 nanoscience & nanotechnology ,Mass spectrometry ,Lignin ,01 natural sciences ,Mass Spectrometry ,0104 chemical sciences ,Analytical Chemistry ,chemistry.chemical_compound ,chemistry ,Ionization ,Ionic liquid ,Degradation (geology) ,Guaiacol ,0210 nano-technology - Abstract
High resolution mass spectrometry was utilized to study the highly complex product mixtures resulting from electrochemical breakdown of lignin. As most of the chemical structures of the degradation products were unknown, enhanced mass defect filtering techniques were implemented to simplify the characterization of the mixtures. It was shown that the implemented ionization techniques had a major impact on the range of detectable breakdown products, with atmospheric pressure photoionization in negative ionization mode providing the widest coverage in our experiments. Different modified Kendrick mass plots were used as a basis for mass defect filtering, where Kendrick mass defect and the mass defect of the lignin-specific guaiacol (C7H7O2) monomeric unit were utilized, readily allowing class assignments independent of the oligomeric state of the product. The enhanced mass defect filtering strategy therefore provided rapid characterization of the sample composition. In addition, the structural similarities between the compounds within a degradation sequence were determined by comparison to a tentatively identified product of this compound series. In general, our analyses revealed that primarily breakdown products with low oxygen content were formed under electrochemical conditions using protic ionic liquids as solvent for lignin.
- Published
- 2015
- Full Text
- View/download PDF
6. Rapid Quantification of Digitoxin and Its Metabolites Using Differential Ion Mobility Spectrometry-Tandem Mass Spectrometry
- Author
-
Uwe Kobold, Roland Thiele, Caroline Bylda, Dietrich A. Volmer, and Alexander Bujotzek
- Subjects
Models, Molecular ,Spectrometry, Mass, Electrospray Ionization ,Electrospray ,Cardiotonic Agents ,Chromatography ,Digitoxin ,Ion-mobility spectrometry ,Tandem mass spectrometry ,Mass spectrometry ,Analytical Chemistry ,Adduct ,Digitoxigenin ,chemistry.chemical_compound ,chemistry ,Limit of Detection ,Tandem Mass Spectrometry ,medicine ,Humans ,Quantitative analysis (chemistry) ,medicine.drug - Abstract
This study focuses on the quantitative analysis of the cardiac glycoside drug digitoxin and its three main metabolites digitoxigenin-bisdigitoxose, digitoxigenin-monodigitoxose, and digitoxigenin using electrospray ionization-differential ion mobility spectrometry-tandem mass spectrometry (ESI-DMS-MS/MS). Despite large molecular weight differences, gas-phase separation of the four compounds in the DMS drift cell was not possible, even by utilizing additional volatile chemical modifiers. Baseline separation was achieved after adduct formation with alkali metal ions, however, and efficiency was shown to improve with increasing size of the alkali ion, reaching optimum conditions for the largest cesium ion. Subsequently, an assay was developed for quantification of digitoxin and its metabolites from human serum samples and its analytical performance assessed in a series of proof-of-concept experiments. The method was applied to spiked human serum pools with concentration levels between 2 and 80 ng/mL. After a short reversed-phase chromatographic step for desalting the sample, rapid DMS separation of the analytes was carried out, resulting in a total run time of less than 1.5 min. The instrumental method showed good repeatability; the calculated coefficients of variation ranged from 2% to 13%.
- Published
- 2015
- Full Text
- View/download PDF
7. Real Time Monitoring of Containerless Microreactions in Acoustically Levitated Droplets via Ambient Ionization Mass Spectrometry
- Author
-
Elizabeth A. Crawford, Dietrich A. Volmer, and Cemal Esen
- Subjects
Chromatography ,Chemistry ,010401 analytical chemistry ,Mixing (process engineering) ,Analytical chemistry ,010402 general chemistry ,Acoustic levitation ,Tandem mass spectrometry ,Mass spectrometry ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,Miniaturization ,Levitation ,Ultrasonic sensor ,Ambient ionization - Abstract
Direct in-droplet (in stillo) microreaction monitoring using acoustically levitated micro droplets has been achieved by combining acoustic (ultrasonic) levitation for the first time with real time ambient tandem mass spectrometry (MS/MS). The acoustic levitation and inherent mixing of microliter volumes of reactants (3 μL droplets), yielding total reaction volumes of 6 μL, supported monitoring the acid-catalyzed degradation reaction of erythromycin A. This reaction was chosen to demonstrate the proof-of-principle of directly monitoring in stillo microreactions via hyphenated acoustic levitation and ambient ionization mass spectrometry. The microreactions took place completely in stillo over 30, 60, and 120 s within the containerless stable central pressure node of an acoustic levitator, thus readily promoting reaction miniaturization. For the evaluation of the miniaturized in stillo reactions, the degradation reactions were also carried out in vials (in vitro) with a total reaction volume of 400 μL. The reacted in vitro mixtures (6 μL total) were similarly introduced into the acoustic levitator prior to ambient ionization MS/MS analysis. The in stillo miniaturized reactions provided immediate real-time snap-shots of the degradation process for more accurate reaction monitoring and used a fraction of the reactants, while the larger scale in vitro reactions only yielded general reaction information.
- Published
- 2016
8. Comparative High-Speed Profiling of Carboxylic Acid Metabolite Levels by Differential Isotope-Coded MALDI Mass Spectrometry
- Author
-
Laura Wang, Dietrich A. Volmer, Albert Koulman, Daniel Petras, and Vinod K. Narayana
- Subjects
chemistry.chemical_classification ,Detection limit ,Chromatography ,Metabolite ,Carboxylic acid ,Fatty Acids ,Carboxylic Acids ,Pyridinium Compounds ,Mass spectrometry ,Analytical Chemistry ,chemistry.chemical_compound ,Matrix-assisted laser desorption/ionization ,Fish Oils ,Metabolomics ,chemistry ,Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ,Metabolome ,Humans ,Gas chromatography ,Derivatization - Abstract
This present work describes the development of a novel high throughput comparative matrix-assisted laser desorption ionization (MALDI) mass spectrometry profiling technique for endogenous compounds using a new isotope-coded label for relative quantitation of carboxylic acids. The key new aspect of this technique was a differential label, 3-hydroxymethyl-1-ethylpyrididinium iodide (HMEP), designed specifically for simultaneous quantitative MALDI analysis of two physiological states. The HMEP-d(0) and HMEP-d(5) variants of the label were applied to profiling endogenous fatty acid levels during a fish oil intervention study, using the metabolite profile of every individual person in the study as their own personal analytical reference standard. Initially, analytical figures of merit such as sensitivity, linear dynamic range, limit of quantitation, and precision were determined from the comparative quantitation experiments. Importantly, the permanently charged HMEP mass tag not only increased the ionization efficiency of the studied fatty acids but also ensured that the solution phase properties of the analytes became more similar, allowing the use of CHCA as a single MALDI matrix compound for the entire range of analytes. The label exhibited a further very unique feature; it provided complete suppression of MALDI matrix-related ions. The MALDI assay was able to generate the data much faster than conventional gas chromatography (GC) methods for fatty acids. It is shown in this study that analyzing a single sample took less than 10 s with analytical results of comparable quality to those obtained by GC.
- Published
- 2009
- Full Text
- View/download PDF
9. Determination of Hyperforin in Mouse Brain by High-Performance Liquid Chromatography/Tandem Mass Spectrometry
- Author
-
Manfred Schubert-Zsilavecz, Walter E. Müller, Jan-Henning Keller, Gunter P. Eckert, Michael Karas, Theodor Dingermann, Dietrich A. Volmer, Mona Tawab, and Henning Blume
- Subjects
Brain Chemistry ,Active ingredient ,Detection limit ,Spectrometry, Mass, Electrospray Ionization ,Chromatography ,Molecular Structure ,Terpenes ,Electrospray ionization ,Body Weight ,Administration, Oral ,Hypericum perforatum ,Reversed-phase chromatography ,Phloroglucinol ,Tandem mass spectrometry ,Sensitivity and Specificity ,High-performance liquid chromatography ,Analytical Chemistry ,Bridged Bicyclo Compounds ,Mice ,Hyperforin ,chemistry.chemical_compound ,chemistry ,Animals ,Female ,Chromatography, High Pressure Liquid - Abstract
Hyperforin is one of the essential active ingredients of St. John's wort extract, which is used as an antidepressant for mild to moderately severe depressions. In vitro and in vivo data as well as several clinical studies and meta analyses have confirmed the pharmacological effect of treatment with hyperforin-containing preparations. However, little is known about the brain availability of hyperforin until now. Accordingly, a highly sensitive and selective LC/MS method for this purpose was developed and validated. This method proved suitable for the determination of hyperforin in mouse brain, after oral administration of hyperforin sodium salt and St. John's wort extract. This method involves liquid-liquid extraction of hyperforin with ethyl acetate followed by separation with rapid reversed-phase high-performance liquid chromatography and tandem mass spectrometry detection using electrospray ionization. Excellent linearity was obtained for the entire calibration range from 0.25 to 10 ng/mL (corresponding to 2.5-100 ng/g brain tissue concentration, calculated with the factor derived from sample processing) with an average coefficient of correlation of 0.9992. The recovery of hyperforin from mouse brain homogenates was between 71.4 and 75.3% with a relative standard deviation of less than 3%. Validation assays for the lower limit of quantitation yielded an accuracy of 5.8%. Intraday accuracy and precision for the developed method were between 4.6 and 10.6% and 4.3-8.4%, respectively, while the interday parameters varied between 6.7 and 12.2% for accuracy and 2.0-5.0% for precision. After the method validation, hyperforin brain levels in mice, treated with 15 mg/kg hyperforin (either as the sodium salt or as 5% St. John's wort extract), were investigated. The average concentration of hyperforin found for the sodium salt group was 28.8+/-10.1 ng/g of brain (n = 8), which was somewhat higher than the hyperforin concentration of 15.8+/-10.9 ng/g of brain (n = 8), determined in the extract-treated group. This method is robust, selective, and highly sensitive and represents an appropriate tool to further prove the occurrence and distribution of hyperforin in mouse brain.
- Published
- 2003
- Full Text
- View/download PDF
10. Study of 4-Quinolone Antibiotics in Biological Samples by Short-Column Liquid Chromatography Coupled with Electrospray Ionization Tandem Mass Spectrometry
- Author
-
Steven J. Locke, Dietrich A. Volmer, and and Bashir Mansoori
- Subjects
Electrospray ,Chemical ionization ,4-Quinolones ,Chromatography ,Chemistry ,Electrospray ionization ,Analytical chemistry ,Extractive electrospray ionization ,Tandem mass spectrometry ,High-performance liquid chromatography ,Mass Spectrometry ,Analytical Chemistry ,Milk ,Anti-Infective Agents ,Animals ,Humans ,Direct electron ionization liquid chromatography–mass spectrometry interface ,Quantitative analysis (chemistry) ,Chromatography, High Pressure Liquid - Abstract
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.
- Published
- 1997
- Full Text
- View/download PDF
11. Detection and confirmation of N-nitrosodialkylamines using liquid chromatography-electrospray ionization coupled on-line with a photolysis reactor
- Author
-
Dietrich A. Volmer, Stanley M. Billedeau, J. O. Lay, and David L. Vollmer
- Subjects
Detection limit ,Electrospray ,Chromatography ,Spectrometer ,Chemistry ,Ionization ,Electrospray ionization ,Photodissociation ,Analytical chemistry ,Mass spectrometry ,Dissociation (chemistry) ,Analytical Chemistry - Abstract
Simultaneous detection and confirmation of several N-nitrosodialkylamines are accomplished by on-line coupling of a photolysis reactor with an HPLC-electrospray ionization mass spectrometer. Several parameters such as irradiation wavelength, irradiation time, mobile-phase composition, and pH, as well as different organic acid modifiers are investigated, and their impact on the detection of the N-nitrosodialkylamine-acid complex and its dissociative photolysis products is presented here. Additionally, the type of structural information obtained from the photolytic processes of N-nitrosodialkylamines is compared to that obtained by using in-source collision-induced dissociation. To demonstrate the potential of this technique, six N-nitrosodialkylamines are studied to determine the linearity of the response, the limits of detection and confirmation, and the reproducibility. The technique's versatility is also exhibited by utilizing negative-ion mode as a complementary means for analysis of the compounds. Finally, an illustrative application for N-nitrosodimethylamine analysis in beer is described.
- Published
- 2011
12. Comprehensive lipidomics analysis of bioactive lipids in complex regulatory networks
- Author
-
Mojgan Masoodi, David Spaner, Dietrich A. Volmer, Albert Koulman, and Michael Eiden
- Subjects
Detection limit ,Chromatography, Reverse-Phase ,Spectrometry, Mass, Electrospray Ionization ,Chromatography ,Chemistry ,Analytical technique ,Solid Phase Extraction ,Mass spectrometry ,Tandem mass spectrometry ,Orbitrap ,Analytical Chemistry ,law.invention ,law ,Cell Line, Tumor ,Lipidomics ,Eicosanoids ,Humans ,Solid phase extraction ,Quadrupole ion trap ,Chromatography, High Pressure Liquid ,Metabolic Networks and Pathways ,Signal Transduction - Abstract
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.
- Published
- 2010
13. Comparison of MALDI to ESI on a triple quadrupole platform for pharmacokinetic analyses
- Author
-
Kevin P. Bateman, Dietrich A. Volmer, Lekha Sleno, Renata Oballa, Jay Corr, Claudio Sturino, and Timo Mauriala
- Subjects
Chemical ionization ,Electrospray ,Spectrometry, Mass, Electrospray Ionization ,Chromatography ,Chemistry ,Electrospray ionization ,Analytical chemistry ,Mass spectrometry ,Analytical Chemistry ,Triple quadrupole mass spectrometer ,Rats ,Standard curve ,Rats, Sprague-Dawley ,Matrix-assisted laser desorption/ionization ,Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ,Animals ,Sample preparation ,Pharmacokinetics - Abstract
This present work describes the systematic experimental comparison of electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) for pharmacokinetic (PK) analysis of two drug candidates from rat plasma using single reaction monitoring (SRM) on a triple quadrupole mass spectrometer. The electrospray assay is an established method using a fast liquid chromatography (LC) separation of the sample extracts prior to mass spectrometry analysis. The novel MALDI assays measured the concentration levels of the drug candidates directly from the spotted sample extracts. Importantly, for both LC-ESI and MALDI the same solid-phase sample extraction protocol, internal standards, triple quadrupole mass analyzer platform, and SRM conditions were used, thus effectively standardizing all experimental parameters of the two assays. Initially, analytical figures of merit such as linearity, limit of quantitation, precision, and accuracy were determined from the calibration curves, indicating very similar performance for both LC-ESI and MALDI. Moreover, the LC-ESI rat plasma concentration time profiles of the drug candidates after orally dosing the animals were accurately reproduced by the MALDI assay, giving virtually identical PK results. The direct MALDI assay, however, was able to generate the data at least 50 x faster than the LC-ESI assay. It is shown in this study that analyzing the entire PK curve for one animal took less than 2 min using MALDI (with five replicate analyses per sample), whereas the corresponding LC-ESI assay required 80 min, however, allowing only two replicate measurements in that time frame.
- Published
- 2007
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.