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Research Interests:
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Increasing evidence suggests a role for the gut microbiome in central nervous system disorders and a specific role for the gut-brain axis in neurodegeneration. Bile acids (BAs), products of cholesterol metabolism and clearance, are... more
Increasing evidence suggests a role for the gut microbiome in central nervous system disorders and a specific role for the gut-brain axis in neurodegeneration. Bile acids (BAs), products of cholesterol metabolism and clearance, are produced in the liver and are further metabolized by gut bacteria. They have major regulatory and signaling functions and seem dysregulated in Alzheimer's disease (AD). Serum levels of 15 primary and secondary BAs and their conjugated forms were measured in 1464 subjects including 370 cognitively normal older adults, 284 with early mild cognitive impairment, 505 with late mild cognitive impairment, and 305 AD cases enrolled in the AD Neuroimaging Initiative. We assessed associations of BA profiles including selected ratios with diagnosis, cognition, and AD-related genetic variants, adjusting for confounders and multiple testing. In AD compared to cognitively normal older adults, we observed significantly lower serum concentrations of a primary BA (cholic acid [CA]) and increased levels of the bacterially produced, secondary BA, deoxycholic acid, and its glycine and taurine conjugated forms. An increased ratio of deoxycholic acid:CA, which reflects 7α-dehydroxylation of CA by gut bacteria, strongly associated with cognitive decline, a finding replicated in serum and brain samples in the Rush Religious Orders and Memory and Aging Project. Several genetic variants in immune response-related genes implicated in AD showed associations with BA profiles. We report for the first time an association between altered BA profile, genetic variants implicated in AD, and cognitive changes in disease using a large multicenter study. These findings warrant further investigation of gut dysbiosis and possible role of gut-liver-brain axis in the pathogenesis of AD.
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Alzheimer's disease (AD) is the most common neurodegenerative disease presenting major health and economic challenges that continue to grow. Mechanisms of disease are poorly understood but significant data point to metabolic defects... more
Alzheimer's disease (AD) is the most common neurodegenerative disease presenting major health and economic challenges that continue to grow. Mechanisms of disease are poorly understood but significant data point to metabolic defects that might contribute to disease pathogenesis. The Alzheimer Disease Metabolomics Consortium (ADMC) in partnership with Alzheimer Disease Neuroimaging Initiative (ADNI) is creating a comprehensive biochemical database for AD. Using targeted and non- targeted metabolomics and lipidomics platforms we are mapping metabolic pathway and network failures across the trajectory of disease. In this report we present quantitative metabolomics data generated on serum from 199 control, 356 mild cognitive impairment and 175 AD subjects enrolled in ADNI1 using AbsoluteIDQ-p180 platform, along with the pipeline for data preprocessing and medication classification for confound correction. The dataset presented here is the first of eight metabolomics datasets being g...
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Our basic understanding of ascending thoracic aortic aneurysm (ATAA) pathogenesis is still very limited, hampering early diagnosis, risk prediction, and development of treatment options. "Omics"-technologies, ideal to reveal... more
Our basic understanding of ascending thoracic aortic aneurysm (ATAA) pathogenesis is still very limited, hampering early diagnosis, risk prediction, and development of treatment options. "Omics"-technologies, ideal to reveal tissue alterations from the normal physiological state due to disease have hardly been applied in the field. Using a metabolomic approach, with this study the authors seek to define tissue differences between controls and various forms of ATAAs. Using a targeted FIA-MS/MS metabolomics approach, we analysed and compared the metabolic profiles of ascending thoracic aortic wall tissue of age-matched controls (n = 8), bicuspid aortic valve-associated aneurysms (BAV-A; n = 9), tricuspid aortic valve-associated aneurysms (TAV-A; n = 14), and tricuspid aortic valve-associated aortic dissections (TAV-Diss; n = 6). With sphingomyelin (SM) (OH) C22:2, SM C18:1, SM C22:1, and SM C24:1 only 4 out of 92 detectable metabolites differed significantly between controls...
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Hyperlipidemia is a risk factor for initiation and progression of diabetic nephropathy but the metabolic pathways altered in the diabetic kidney in a context of hyperlipidemia remain incompletely described. Assuming that changes in urine... more
Hyperlipidemia is a risk factor for initiation and progression of diabetic nephropathy but the metabolic pathways altered in the diabetic kidney in a context of hyperlipidemia remain incompletely described. Assuming that changes in urine composition reflect the alteration of renal metabolism and function, we analyzed the urine metabolite composition of diabetic (streptozotocin-treatment) and control (non diabetic) ApoE-/- mice fed a high cholesterol diet using targeted quantitative metabolomics. Urine metabolome was also compared to the plasma metabolome of the same animals. As previously shown, urine albuminuria/urine creatinine ratio (uACR) and glomerular area and plasma lipids (cholesterol, triglycerides) were more elevated in diabetic mice compared to control. After adjustment to urine creatinine, the abundance of 52 urine metabolites was significantly different in diabetic mice compared to control. Among them was a unique metabolite, C14:2-OH (3-hydroxytetradecadienoylcarnitine...
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Today, the technology of 'targeted' based metabolomics is pivotal in the clinical analysis workflow as it provides information of metabolic phenotyping (metabotypes) by enhancing our understanding of metabolism of complex... more
Today, the technology of 'targeted' based metabolomics is pivotal in the clinical analysis workflow as it provides information of metabolic phenotyping (metabotypes) by enhancing our understanding of metabolism of complex diseases, biomarker discovery for disease development, progression, treatment, and drug function and assessment. This review is focused on surveying and providing a gap analysis on metabolic phenotyping with a focus on targeted based metabolomics from an instrumental, technical point-of-view discussing the state-of-the-art instrumentation, pre- to post- analytical aspects as well as an overall future necessity for biomarker discovery and future (pre-) clinical routine application.
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Research Interests: Analytical Chemistry, Mass Spectrometry, Metabolomics, Quantitative analysis, Brain, and 11 moreBiomedical Research, Animals, Molecular Mass, Quantitative Analysis, Analytical Biochemistry, Multiple Objectives, Sus Scrofa, Physicochemical Properties, Metabolome, Biochemistry and cell biology, and Solvents
ABSTRACT According to recent investigations on fault mechanisms in nano-scale integrated circuits, they suffer from wear-out effects that limit their life time seriously. For application that combine a long life time and safety-critical... more
ABSTRACT According to recent investigations on fault mechanisms in nano-scale integrated circuits, they suffer from wear-out effects that limit their life time seriously. For application that combine a long life time and safety-critical functionality, means of fault compensation, de-stressing and eventual self repair are therefore becoming a must. While built-in self repair (BISR) is state-of-the-art in memory blocks and in FPGA, it is much more difficult to implement in irregular logic blocks. In this paper, we introduce a circuit architecture that combines capabilities of self repair and de-stressing. The necessary overhead can be estimated, and limitations as well as “single points of failure” are discussed.
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Page 1. Simultaneous Determination of a Wide Spectrum of Pesticides in Water by Means of Fast On-line SPE-HPLC-MS-MS - a Novel Approach 2003,57, Suppl.,S-93 S-101 T. Koal* / A. Asperger / J. Efer / W. Engewald Leipzig ...
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Background / Purpose: We illustrate how metabolic phenotyping could support diagnosis and disease prediction, along with the prognosis of the potential of a certain therapy, by two examples from Alzheimer´s disease research. Main... more
Background / Purpose: We illustrate how metabolic phenotyping could support diagnosis and disease prediction, along with the prognosis of the potential of a certain therapy, by two examples from Alzheimer´s disease research. Main conclusion: In combination with other “omics”-techniques, metabolic phenotyping supports the identification of gene function and provides a complete biological system diagnosis for an improved personalized medicine approach.
Alzheimer's disease (AD) is a severe and chronic neurodegenerative disorder of the brain. The laboratory diagnosis is limited to the analysis of three biomarkers in cerebrospinal fluid (CSF): amyloid-β42 (Aβ42), total tau, and... more
Alzheimer's disease (AD) is a severe and chronic neurodegenerative disorder of the brain. The laboratory diagnosis is limited to the analysis of three biomarkers in cerebrospinal fluid (CSF): amyloid-β42 (Aβ42), total tau, and phospho-tau-181 (P-tau-181). However, there is a need to find more biomarkers in CSF that can improve the sensitivity and specificity. The aim of the present study was to analyze endogenous small metabolites (metabolome) in the CSF, which may provide potentially new insights into biochemical processes involved in AD. One hundred CSF samples were dichotomized by normal (n = 50) and pathological decreased Aβ42 and increased tau and P-tau-181 levels (n = 50; correlating to an AD-like pathology). These CSF samples were analyzed using the AbsoluteIDQ® p180 Kit (BIOCRATES Life Sciences), which included 40 acyl carnitines metabolites, 21 amino acids, 19 proteinogenic aminoacids, 15 sphingolipids, and 90 glycerophospholipids. Our data show that two sphingomyelins ...
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The authors have investigated whether cyclosporine decreases the serum concentration of mycophenolic acid, the active principle of the immunosuppressant mycophenolate mofetil, and increases that of the inactive metabolite 7-O-mycophenolic... more
The authors have investigated whether cyclosporine decreases the serum concentration of mycophenolic acid, the active principle of the immunosuppressant mycophenolate mofetil, and increases that of the inactive metabolite 7-O-mycophenolic acid glucuronide by reducing their enterohepatic recirculation. Rats were treated daily with methylcellulose (1.66 mL/kg PO) plus 0.9% NaCl (6 mL/kg IP), mycophenolate mofetil (20 mg/kg PO) plus 0.9% NaCl (6 mL/kg IP), methylcellulose (1.66 mL/kg PO) plus cyclosporine (5 mg/kg IP), and mycophenolate mofetil (20 mg/kg PO) plus cyclosporine (5 mg/kg IP). After 14 days a bile fistula was installed to measure the biliary excretion of the immunosuppressants and their metabolites. After 90 minutes blood was taken to determine their concentrations in blood or serum by HPLC. Cyclosporine significantly decreased the serum concentration of mycophenolic acid by 39% and increased, not significantly, that of 7-O-mycophenolic acid glucuronide by 53%. The biliary excretion of 7-O-mycophenolic acid glucuronide was significantly reduced by cyclosporine by 57%, whereas that of mycophenolic acid was not affected. Mycophenolate mofetil did not show a significant effect on either the blood concentration or the biliary excretion of cyclosporine and its metabolites AM1, AM9, AM1c, and AM4N. Cyclosporine significantly decreased the serum concentration of active mycophenolate acid and increased, not significantly, the serum concentration of inactive 7-O-mycophenolic acid glucuronide, presumably by reducing the biliary excretion of this inactive metabolite.
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Research Interests:
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For the first time approved antiretroviral drugs, i.e. protease inhibitors (PI) and non-nucleoside reverse transcriptase inhibitors (NNRTI), were quantified in dried blood spots (DBS) from HIV/AIDS patient whole blood samples as the basis... more
For the first time approved antiretroviral drugs, i.e. protease inhibitors (PI) and non-nucleoside reverse transcriptase inhibitors (NNRTI), were quantified in dried blood spots (DBS) from HIV/AIDS patient whole blood samples as the basis for therapeutic drug monitoring (TDM) by a robust simultaneous liquid chromatography/tandem mass spectrometry (LC/MS/MS) method. This study included seven PI (amprenavir, nelfinavir, indinavir, lopinavir, saquinavir, ritonavir, atazanavir) and two NNRTI (nevirapine, efavirenz). LC/MS/MS coupling was realized using a Phenomenex Synergy Max RP LC column (150 x 2 mm, 4 micro) in combination with a tandem mass spectrometer (API 2000, Applied Biosystems/MDS Sciex Concord) operating in positive and negative multiple reaction monitoring (MRM) mode with reserpine as internal standard. DBS samples were punched out and extracted with 50:50 MeOH/0.2 M ZnSO4 (v/v) as extraction reagent. The method performance data for the drugs in DBS like limits of detection (LOD, 8-70 ng/mL), lower limits of quantification (LLOQ, 41-102 ng/mL), linearity (R2, 0.9981-0.9999), linear concentration ranges (41-10.000 ng/mL), accuracies (92-113%), recoveries (62-94%), and ion suppression were investigated and are comparable to data obtained from human plasma, which is the current standard matrix for TDM of PI and NNRTI. In this case, off-line plasma sample preparation was performed by means of simple protein precipitation with 80:20 methanol/0.2 M ZnSO4 (v/v) as precipitation reagent. Significant correlations between real patient plasma and DBS were obtained for samples containing lopinavir, atazanavir, ritonavir, saquinavir, and efavirenz. DBS preparation as sampling alternative is well suited and practicable for TDM minimizing the high infection risk of HIV/AIDS samples and may facilitate sample mailing.
Research Interests: Earth Sciences, Biological Sciences, Therapeutic drug monitoring, Humans, Tandem Mass Spectrometry, and 9 moreHigh Pressure Liquid Chromatography, CHEMICAL SCIENCES, Liquid Chromatography / Electrospray Ionization Mass Spectrometry, Liquid Chromatography, Reproducibility of Results, Dried Blood Spot, Acquired immunodeficiency syndrome, Blood Specimen Collection, and reverse transcriptase inhibitors
Isotope correction of a profile is an important step in the analysis of mass spectrometry derived data. The problem is mathematically formulated as a system of linear equations which is general enough to include previous correction... more
Isotope correction of a profile is an important step in the analysis of mass spectrometry derived data. The problem is mathematically formulated as a system of linear equations which is general enough to include previous correction methods. For the solution of these equations when applied to the whole profile an efficient algorithm is developed. In experimental tests the resulting algorithm corrected the profile fast and successfully.
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We investigated the inhibitory effects of curcumin, curcumin derivatives and degradation products on OKT3-induced human peripheral blood mononuclear cell (PBMC) proliferation and the role of their radical scavenging activity. OKT3-induced... more
We investigated the inhibitory effects of curcumin, curcumin derivatives and degradation products on OKT3-induced human peripheral blood mononuclear cell (PBMC) proliferation and the role of their radical scavenging activity. OKT3-induced human PBMC proliferation was determined by measuring 3H-thymidine incorporation. Radical scavenging activity was evaluated by using an in vitro DPPH assay. OKT3-induced PBMC proliferation was inhibited by curcumin, isocurcumin, bisdesmethoxy-, diacetyl-, tetrahydro-, hexahydro-, and octahydrocurcumin as well as by vanillin, ferulic acid, and dihydroferulic acid with IC50-values of 2.8, 2.8, 6.4, 1.0, 25, 38, 82, 729, 457, and >1,000 microM, respectively. The investigated substances with the strongest effect on radical scavenging were tetrahydro-, hexahydro-, and octahydrocurcumin with IC50 values of 10.0, 11.7, and 12.3 microM, respectively. IC50-values of dihydroferulic acid, ferulic acid, and curcumin were 19.5, 37, and 40 microM. The substances with the lowest radical scavenging activities were vanillin, isocurcumin, diacetylcurcumin, and bisdesmethoxycurcumin with IC50 values higher than 100 microM each. Curcuminoid-induced inhibition of OKT3-induced PBMC proliferation depends on the number of carbon atoms and double bonds of the 1,6-heptadiene-3,5-dione structure as well as on the phenolic ring substitutes of the curcuminoids but is not correlated to their respective radical scavenging activity.
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Research Interests: Analytical Chemistry, Mass Spectrometry, Robustness Analysis, Therapeutic drug monitoring, Humans, and 13 moreSolid Phase Extraction, Organ Transplantation, Atmospheric Pressure, Tandem Mass Spectrometry, High Performance Liquid Chromatography, High Pressure Liquid Chromatography, High Speed, Very high throughput, Reproducibility of Results, Sensitivity and Specificity, Biochemistry and cell biology, Immunosuppressive Agents, and Pharmacology and pharmaceutical sciences
Research Interests: Engineering, Technology, Mass Spectrometry, Water Pollution, Sample Preparation, and 15 moreElectrospray, Pesticide, Solid Phase Extraction, Pesticides, Drinking Water, Atmospheric Pressure, Tandem Mass Spectrometry, Chemical Analysis, High Pressure Liquid Chromatography, CHEMICAL SCIENCES, Liquid Chromatography / Electrospray Ionization Mass Spectrometry, Liquid Chromatography, Flow Rate, Electrospray Ionization, and HPLC Chromatography
An integrated on-line SPE-HPLC-MS/MS system has been developed for the rapid analysis of various trace level priority pesticides in surface and drinking water. Eleven pesticides were included in this study, with various phenylureas,... more
An integrated on-line SPE-HPLC-MS/MS system has been developed for the rapid analysis of various trace level priority pesticides in surface and drinking water. Eleven pesticides were included in this study, with various phenylureas, triazines and organophosphorous species among them. Use of turbulent-flow chromatography columns (TFC, 50 x 1 mm, 30-50 microm particle size) as extraction cartridges enables fast on-line SPE at high sampling flow-rate (5 ml/min). Polymeric and carbon based TFC columns (Oasis HLB, Cyclone, Hypercarb) allow complete extraction with good recoveries from water volumes up to 50 ml. On-line coupling to HPLC is performed with re-mixing of the organic TFC eluate with water in front of the analytical column to ensure efficient band focussing. For fast HPLC analysis, a short monolithic column is applied in combination with highly selective API-MS/MS detection. Matrix effects on the APCI-MS/MS signal were found to be reduced by the system to an acceptable minimum. Limits of detection, determined for 10-ml samples of river water were in the range between 0.4 and 13 ng/l typically, except trifluralin (approximately 280 ng/l), which is less susceptible to ionization under atmospheric pressure conditions. At an enriched water volume of 10 ml, the whole SPE-HPLC-MS/MS procedure requires less than 14 min. The method was successfully applied to the analysis of drinking and surface water samples taken from several sampling sites around the city of Leipzig, Germany. Concentrations measured (maximum: 16 ng/l simazine in river water) were far below the concentration limits scheduled by law.
Research Interests: Engineering, Technology, Mass Spectrometry, Solid Phase Extraction, Pesticides, and 14 moreRiver water, Drinking Water, Surface Water, Atmospheric Pressure, Tandem Mass Spectrometry, Turbulent Flow, High Pressure Liquid Chromatography, CHEMICAL SCIENCES, High Speed, Water Analysis, Particle Size, Liquid Chromatography, Flow Rate, and limit of detection
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Research Interests:
The gap of the post-genomic era is increasingly being filled by the metabolomics approach, comprising a technology for analyzing small molecule endogenous metabolites (<1500 Dalton) in complex biological samples. This new... more
The gap of the post-genomic era is increasingly being filled by the metabolomics approach, comprising a technology for analyzing small molecule endogenous metabolites (<1500 Dalton) in complex biological samples. This new analytical science has progressed within the last years particularly with regard to improvements in mass spectrometry based detection, now allowing highly robust, reproducible, selective and sensitive qualitative or quantitative analysis of endogenous metabolites. The precise and accurate quantitation of these metabolites via targeted metabolomics, now critically contributes to the quantitative analysis of endogenous compounds in biomarker discovery and validation thus to future personalized therapy. The analytical methods of choice in (MS-based) targeted metabolomics primarily are HPLC-API-MS/MS, FIA-APIMS/MS and GC-MS. In the parent paper, we provide an introduction and brief survey on the technological basis of targeted metabolomics in biomarker research, discuss various relevant analytical aspects in mass spectrometry including comparison to non-targeted approaches, effects of sample preparation, impact of sample stability, carryover- and matrix effects, need for standardization and for proficiency tests, standardization of analytical methods as well as the requirement for method validation.
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Fatty acid metabolites play a key role in numerous physiological and pathological processes. A rapid liquid chromatography-mass spectrometry assay for the simultaneous determination of prostanoids, isoprostane and lipoxygenase (LOX)... more
Fatty acid metabolites play a key role in numerous physiological and pathological processes. A rapid liquid chromatography-mass spectrometry assay for the simultaneous determination of prostanoids, isoprostane and lipoxygenase (LOX) derived fatty acid metabolites in a small biological sample of only 20 microL was developed. Human plasma samples were applied to a filter spot, extracted without prior derivatization and analyzed within 13 min. Detection of metabolites was performed on a triple quadrupole mass spectrometer in negative multiple-reaction monitoring detection mode. Application of this assay to various biological matrices was performed. The validated assay was linear over the concentration range of 5-500 nmol/L for prostanoids and isoprostane, 50-5000 nmol/L for LOX-derived metabolites and 400-40,000 nmol/L for fatty acids. Limits of quantitation were 0.4-233 nmol/L, depending on the metabolite. Plasma samples from diabetic patients and controls showed significant increases in (+/-)9-HODE and 15(S)-HETE with p-values of 0.019 and 0.024, respectively. The small amount of 20 microL sample volume used in this assay and the demonstrated application to various sample types makes it an ideal routine analysis method for fatty acid metabolites. The resulting values for LOX-derived metabolites in diabetes mellitus type 2 samples support earlier findings about the role of lipid oxidation products in diabetes.
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In this study antiretroviral drugs of the classes protease inhibitors (PI) and non-nucleoside reverse transcriptase inhibitors (NNRTI) were quantified for the first time directly in patient plasma samples by means of an automated and... more
In this study antiretroviral drugs of the classes protease inhibitors (PI) and non-nucleoside reverse transcriptase inhibitors (NNRTI) were quantified for the first time directly in patient plasma samples by means of an automated and validated online solid-phase extraction-liquid chromatography-tandem mass spectrometry (XLC-MS/MS) method using the Symbiosis Pharma system (Spark Holland) for XLC coupled to an API 2000 for MS/MS analysis. The PI drugs amprenavir, nelfinavir, indinavir, lopinavir, saquinavir, ritonavir, and atazanavir, and the NNRTI drugs nevirapine and efavirenz in real patient samples were analysed in a 25-microL sample volume, which was only diluted with 200 microL of H2O (containing 500 ng/mL of the internal standard reserpine) to minimise the matrix concentration and to add the internal standard. No additional tedious and time-consuming sample preparation steps such as protein precipitation, centrifugation, and pipetting were per-formed for sample clean-up. The high-throughput method developed allowed the simultaneous analysis of two samples (first analysis 6.6 min, subsequent analyses 3.3 min between injections) and has been validated in terms of the limit of detection (LOD, 2-70 ng/mL), lower limit of quantification (LLOQ, 78-156 ng/mL), linearity (R2, 0.9971-0.9989), linear concentration range (from LLOQ to 10,000 ng/mL), intra- and inter-day precision (< 13.5% at LLOQ, < 7.5% at high concentrations), proficiency testing accuracy (78-127%), laboratory internal accuracy (86-113%), recovery (60-110%), and drug stability (freeze-thaw, short-term temperature, long-term and post-preparative) and inter-subject variability. Although direct analysis of diluted plasma was performed, post-column experiments showed efficient matrix minimisation by the XLC-MS/MS technique, which is perfectly appropriate for routine therapeutic drug monitoring of HIV/AIDS patient samples.
Research Interests: Cognitive Science, Mass Spectrometry, Humans, Automation, Solid Phase Extraction, and 10 moreTandem Mass Spectrometry, High Performance Liquid Chromatography, Clinical Sciences, High Pressure Liquid Chromatography, Liquid Chromatography, Time Factors, Reproducibility of Results, Sensitivity and Specificity, Antiviral Agents, and reverse transcriptase inhibitors
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Research Interests: Mass Spectrometry, Therapeutic drug monitoring, Humans, Calibration, Clinical Sciences, and 9 moreHigh Pressure Liquid Chromatography, Liquid Chromatography / Electrospray Ionization Mass Spectrometry, Beta Lactams, Carbapenems, Reproducibility of Results, LC MS, Chronic Kidney Failure, Drug Stability, and Reference standards
Page 1. Simultaneous Determination of a Wide Spectrum of Pesticides in Water by Means of Fast On-line SPE-HPLC-MS-MS - a Novel Approach 2003,57, Suppl.,S-93 S-101 T. Koal* / A. Asperger / J. Efer / W. Engewald Leipzig ...
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Research Interests:
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As the lipidomics field continues to advance, self-evaluation within the community is critical. Here, we performed an interlaboratory comparison exercise for lipidomics using Standard Reference Material (SRM) 1950 Metabolites in Frozen... more
As the lipidomics field continues to advance, self-evaluation within the community is critical. Here, we performed an interlaboratory comparison exercise for lipidomics using Standard Reference Material (SRM) 1950 Metabolites in Frozen Human Plasma, a commercially available reference material. The interlaboratory study comprised 31 diverse laboratories, with each lab using a different lipidomics workflow. A total of 1527 unique lipids were measured across all laboratories, and consensus location estimates and associated uncertainties were determined for 339 of these lipids measured at the sum composition level by five or more participating laboratories. These evaluated lipids detected in SRM 1950 serve as community-wide benchmarks for intra- and inter-laboratory quality control and method validation. These analyses were performed using non-standardized laboratory-independent workflows. The consensus locations were also compared to a previous examination of SRM 1950 by the LIPID MAPS...