TY  - JOUR
AB  - This study concerns the synthesis of the florfenicol (FF) metabolites florfenicol amine (FFA), florfenicol alcohol (FFOH), and monochloroflorfenicol (FFCl), for their subsequent use as reference standards in On-line solid-phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry (SPE-UHPLC-MS/MS) analysis. The metabolites were characterized using 1H and 13C NMR, as well as HRMS, and their purities were confirmed by quantitative NMR to ensure analytical reliability. Validation of the developed analytical method showed that it presented acceptable performance, with linearity >0.99 for all the target analytes, accuracies within ±10 % of nominal concentrations, and intra- and inter-day precisions within 15 %. Application of this method to fillets from fish that had been treated with florfenicol (dose of 10 mg/kg bw daily) demonstrated its effectiveness in consistently detecting FF and its metabolites throughout the treatment. The results emphasized the utility of the method for enhancing pharmacokinetic and residue depletion research. The ability to precisely monitor the drug and its metabolites in treated fish provides important insights into florfenicol metabolism, laying the groundwork for further comprehensive profiling studies of metabolites in fish tissue.
AU  - Paula Rocha de Queiroga, A.*
AU  - Freitas Pereira de Souza, G.*
AU  - Mateus Assane, I.*
AU  - Messias, T.*
AU  - Pilarski, F.*
AU  - Schloter, M.
AU  - Gonçalves Salles, A.*
AU  - Rath, S.*
C1  - 71568
C2  - 56280
CY  - Radarweg 29, 1043 Nx Amsterdam, Netherlands
TI  - Quantification of florfenicol and its metabolites in fillets of Nile tilapia: Synthesis of metabolites and validation of an on-line solid-phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry method.
JO  - J. Chromatogr. B
VL  - 1246
PB  - Elsevier
PY  - 2024
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - Lipidomics is focusing on the screening of lipid species in complex mixtures using mass spectrometry-based approaches. In this work, we aim to enhance the intestinal lipidome coverage within the Oligo-Mouse-Microbiota (OMM12) colonized mouse model by testing eight mobile phase conditions on five reversed-phase columns. Our selected mobile phase modifiers included two ammonium salts, two concentrations, and the addition of respective acids at 0.1 %. We compared two columns with hybrid surface technology, two with ethylene bridged hybrid technology and one with core–shell particles. Best performance was attained for standards and intestinal lipidome, using either ammonium formate or acetate in ESI(+) or ammonium acetate in ESI(−) for all column technologies. Notably, a concentration of 5 mM ammonium salt showed optimal results for both modes, while the addition of acids had a negligible effect on lipid ionization efficiency. The HST BEH C18 column improved peak width and tailing factor parameters compared to other technologies. We achieved the highest lipid count in colon and ileum content, including ceramides, phosphatidylethanolamines and phosphatidylcholines, when using 5 mM ammonium acetate in ESI(−). Conversely, in ESI(+) 5 mM ammonium formate demonstrated superior coverage for diacylglycerols and triacylglycerols.
AU  - Selmi, H.
AU  - Walker, A.
AU  - Debarbieux, L.*
AU  - Schmitt-Kopplin, P.
C1  - 70897
C2  - 55797
CY  - Radarweg 29, 1043 Nx Amsterdam, Netherlands
TI  - Improving the intestinal lipidome coverage in a gnotobiotic mouse model using UHPLC-MS-based approach through optimization of mobile phase modifiers and column selection.
JO  - J. Chromatogr. B
VL  - 1242
PB  - Elsevier
PY  - 2024
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - Metabolomics deals with the large-scale analysis of metabolites, belonging to numerous compound classes and showing an extremely high chemical diversity and complexity. Lipidomics, being a subcategory of metabolomics, analyzes the cellular lipid species. Both require state-of-the-art analytical methods capable of accessing the underlying chemical complexity. One of the major techniques used for the analysis of metabolites and lipids is Liquid Chromatography-Mass Spectrometry (LC-MS), offering both different selectivities in LC separation and high sensitivity in MS detection. Chromatography can be divided into different modes, based on the properties of the employed separation system. The most popular ones are Reversed-Phase (RP) separation for non– to mid-polar molecules and Hydrophilic Interaction Liquid Chromatography (HILIC) for polar molecules. So far, no single analysis method exists that can cover the entire range of metabolites or lipids, due to the huge chemical diversity. Consequently, different separation methods have been used for different applications and research questions. In this review, we explore the current use of LC-MS in metabolomics and lipidomics. As a proxy, we examined the use of chromatographic methods in the public repositories EBI MetaboLights and NIH Metabolomics Workbench. We extracted 1484 method descriptions, collected separation metadata and generated an overview on the current use of columns, eluents, etc. Based on this overview, we reviewed current practices and identified potential future trends as well as required improvements that may allow us to increase metabolite coverage, throughput or both simultaneously.
AU  - Harrieder, E.-M.
AU  - Kretschmer, F.*
AU  - Böcker, S.*
AU  - Witting, M.
C1  - 63743
C2  - 51663
TI  - Current state-of-the-art of separation methods used in LC-MS based metabolomics and lipidomics.
JO  - J. Chromatogr. B
VL  - 1188
PY  - 2022
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - 3-iodothyronamine (3-T1AM) has been suggested as a novel chemical messenger and potent trace amine-associated receptor 1 ligand in the CNS that occurs naturally as endogenous metabolite of the thyroid hormones. Discrepancies and variations in 3-T1AM plasma and tissue concentrations have nonetheless caused controversy regarding the existence and biological role of 3-T1AM. These discussions are at least partially based on potential analytical artefacts caused by differential decay kinetics of 3-T1AM and the widely used deuterated quantification standard D4-T1AM. Here, we report a novel LC-MS/MS method for the quantification of 3-T1AM in biological specimens using stable isotope dilution with 13C6-T1AM, a new internal standard that showed pharmacodynamic properties comparable to endogenous 3-T1AM. The method detection limit (MDL) and method quantification limit (MQL) of 3-T1AM were 0.04 and 0.09 ng/g, respectively. The spike-recoveries of 3-T1AM were between 85.4% and 94.3%, with a coefficient of variation of 3.7–5.8%. The intra-day and inter-day variations of 3-T1AM were 8.45–11.2% and 3.58–5.73%, respectively. Endogenous 3-T1AM liver values in C57BL/6J mice were 2.20 ± 0.49 pmol/g with a detection frequency of 50%. Higher liver 3-T1AM values were found when C57BL/6J mice were treated with N-acetyl-3-iodothyronamine or O-acetyl-3-iodothyronamine. Overall, our new stable isotope dilution LC-MS/MS method improves both the sensitivity and selectivity compared with existing methods. The concomitant possibility to quantify additional thyroid hormones such as thyroxine, 3,5,3′-triiodo-L-thyronine, 3,3′,5′-triiodo-L-thyronine, 3,3′-diiodo-L-thyronine, and 3,5-diiodo-L-thyronine further adds to the value of our novel method in exploring the natural occurrence and fate of 3-T1AM in biological tissues and fluids.
AU  - Li, Z.M.
AU  - Miller, M.
AU  - Gachkar, S.*
AU  - Mittag, J.*
AU  - Schriever, S.C.
AU  - Pfluger, P.T.
AU  - Schramm, K.-W.
AU  - de Angelis, M.
C1  - 61113
C2  - 50050
CY  - Radarweg 29, 1043 Nx Amsterdam, Netherlands
TI  - Determination of 3-iodothyronamine (3-T1AM) in mouse liver using liquid chromatography-tandem mass spectrometry.
JO  - J. Chromatogr. B
VL  - 1165
PB  - Elsevier
PY  - 2021
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - The fecal metabolome is a complex mixture of endogenous, microbial metabolites, and food derived compounds. Hydrophilic interaction liquid chromatography (HILIC) enables the analysis of polar compounds, which is a valuable alternative to reversed-phase liquid chromatography in the field of metabolomics due to its ability to retain a greater portion of the polar metabolome. The objective of the study was to find the optimal chromatographic solution to perform non-targeted metabolomics of feces by means of HILIC ultra-high-pressure liquid chromatography mass spectrometry (UHPLC-Q-TOF-MS). The performance was systematically investigated analyzing a pooled fecal sample, and mixtures of 150 metabolites from different families, including for example amino acids, amines, indole derivatives, fatty acids and carbohydrates. Three different stationary phases (zwitterionic, amide and unbonded silica) were operated at three pH values (4.6, 6.8 and 9.0), and three salt gradient conditions (5-5, 5-10 and 5-25 mM ammonium acetate). Amide and zwitterionic stationary phases performed similarly at low pH, with highest number of detected standards, which increased by increasing the salt gradient. The amide column showed slightly better performance in terms of separation of isomers and peak widths and remarkably good performance at basic pH, with highest number of metabolite features in the non targeted analysis. The zwitterionic column operated best in terms of number of detected standards, retention time distribution of standards and metabolite feature across whole chromatographic run. Thus, the zwitterionic column was proven to suit for non-targeted analysis of fecal samples, resulting in good coverage of especially amino acids and carbohydrates.
AU  - Sillner, N.
AU  - Walker, A.
AU  - Harrieder, E.-M.
AU  - Schmitt-Kopplin, P.
AU  - Witting, M.
C1  - 55510
C2  - 46368
CY  - Po Box 211, 1000 Ae Amsterdam, Netherlands
SP  - 142-148
TI  - Development and application of a HILIC UHPLC-MS method for polar fecal metabolome profiling.
JO  - J. Chromatogr. B
VL  - 1109
PB  - Elsevier Science Bv
PY  - 2019
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - Bile acids (BAs) are major components of bile synthesized from cholesterol and take part in the digestion of dietary lipids, as well as having signaling functions. They undergo extensive microbial metabolism inside the gastrointestinal tract. Here, we present a method of ultra-high pressure liquid chromatography coupled to ion trap mass spectrometry for quantification of 45 BAs in mouse cecum. The system was validated in regard to sensitivity with limits of detection and quantification (0.6–24.9 nM), interday accuracy (102.4%), interday precision (15.2%), recovery rate (74.7%), matrix effect (98.2%) and carry-over effect ( < 1.1%). Afterwards, we applied our method to investigate the effect of metformin on BA profiles. Diabetic mice were treated with metformin for 1 day or 14 days. One day of treatment resulted in a significant increase of total BA concentration (2.7-fold increase; db/db metformin 5.32 μmol/g, db/db control mice 1.95 μmol/g), most notable in levels of 7-oxodeoxycholic, 3-dehydrocholic and cholic acid. We observed only minor impact on BA metabolism after 14 days of metformin treatment, compared to the single treatment. Furthermore, healthy wild type mice had elevated concentrations of allocholic and ω-muricholic acid compared to diabetic mice. Our method proved the applicability of profiling BAs in cecum to investigate intestinal BA metabolism in diabetes and pharmacological applications.
AU  - Sillner, N.
AU  - Walker, A.
AU  - Koch, W.
AU  - Witting, M.
AU  - Schmitt-Kopplin, P.
C1  - 53220
C2  - 44652
SP  - 35-43
TI  - Metformin impacts cecal bile acid profiles in mice.
JO  - J. Chromatogr. B
VL  - 1083
PY  - 2018
SN  - 1570-0232
ER  - 

TY  - JOUR
AU  - Junot, C.*
AU  - Witting, M.
C1  - 52521
C2  - 44044
CY  - Amsterdam
SP  - 1-2
TI  - Identification of molecules from non-targeted analysis.
JO  - J. Chromatogr. B
VL  - 1071
PB  - Elsevier Science Bv
PY  - 2017
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - Identification of metabolites in non-targeted metabolomics continues to be a bottleneck in metabolomics studies in large human cohorts. Unidentified metabolites frequently emerge in the results of association studies linking metabolite levels to, for example, clinical phenotypes. For further analyses these unknown metabolites must be identified. Current approaches utilize chemical information, such as spectral details and fragmentation characteristics to determine components of unknown metabolites. Here, we propose a systems biology model exploiting the internal correlation structure of metabolite levels in combination with existing biochemical and genetic information to characterize properties of unknown molecules. Levels of 758 metabolites (439 known, 319 unknown) in human blood samples of 2279 subjects were measured using a non-targeted metabolomics platform (LC-MS and GC-MS). We reconstructed the structure of biochemical pathways that are imprinted in these metabolomics data by building an empirical network model based on 1040 significant partial correlations between metabolites. We further added associations of these metabolites to 134 genes from genome-wide association studies as well as reactions and functional relations to genes from the public database Recon 2 to the network model. From the local neighborhood in the network, we were able to predict the pathway annotation of 180 unknown metabolites. Furthermore, we classified 100 pairs of known and unknown and 45 pairs of unknown metabolites to 21 types of reactions based on their mass differences. As a proof of concept, we then looked further into the special case of predicted dehydrogenation reactions leading us to the selection of 39 candidate molecules for 5 unknown metabolites. Finally, we could verify 2 of those candidates by applying LC-MS analyses of commercially available candidate substances. The formerly unknown metabolites X-13891 and X-13069 were shown to be 2-dodecendioic acid and 9-tetradecenoic acid, respectively. Our data-driven approach based on measured metabolite levels and genetic associations as well as information from public resources can be used alone or together with methods utilizing spectral patterns as a complementary, automated and powerful method to characterize unknown metabolites.
AU  - Quell, J.
AU  - Römisch-Margl, W.
AU  - Colombo, M.*
AU  - Krumsiek, J.
AU  - Evans, A.M.*
AU  - Mohney, R.P.*
AU  - Salomaa, V.*
AU  - de Faire, U.*
AU  - Groop, L.C.*
AU  - Agakov, F.V.*
AU  - Looker, H.C.*
AU  - McKeigue, P.M.*
AU  - Colhoun, H.M.*
AU  - Kastenmüller, G.
C1  - 51096
C2  - 43086
CY  - Amsterdam
SP  - 58-67
TI  - Automated pathway and reaction prediction facilitates in silico identification of unknown metabolites in human cohort studies.
JO  - J. Chromatogr. B
VL  - 1071
PB  - Elsevier Science Bv
PY  - 2017
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - Thyroid hormones (THs) play a critical role in the regulation of many biological processes such as growth, metabolism and development both in humans and wildlife. In general, TH levels are measured by immunoassay (IA) methods but the specificity of the antibodies used in these assays limits selectivity. In the last decade, several analytical methods using liquid chromatography-mass spectrometry (LC-MS) and tandem mass spectrometry (LC-MS/MS) have been developed to measure THs. These new techniques proved to be more accurate than the IA analysis and they were widely used for the determination of TH level in different human and animal tissues. A large part of LC-MS/MS methods described in literature employed between 200 and 500mg of sample, however this quantity can be considered too high especially when preclinical studies are conducted using mice as test subjects. Thus an analytical method that reduces the amount of tissue is essential. In this study, we developed a procedure for the analysis of six THs; L-thyroxine (T4), 3,3',5-triiodo-l-thyronine (T3), 3,3',5'-triiodo-l-thyronine (rT3), 3,5-diiodo-l-thyronine (rT2), 3,3'-diiodo-l-thyronine (T2), 3-iodo-l-thyronine (T1) using isotope ((13)C6-T4, (13)C6-T3, (13)C6-rT3, (13)C6-T2) dilution liquid chromatography-mass spectrometry. The major difference with previously described methods lies in the utilization of a nano-UPLC (Ultra Performance Liquid Chromatography) system in micro configuration. This approach leads to a reduction compared to the published methods, of column internal diameter, flow rate, and injected volume. The result of all these improvements is a decrease in the amount of sample necessary for the analysis. The method was tested on six different mouse tissues: liver, heart, kidney, muscle, lung and brown adipose tissue (BAT). The nano-UPLC system was interfaced with a quadrupole time-of-flight mass spectrometer (Q-TOF2-MS) using the positive ion mode electrospray ionization. In our analytical method the instrumental calibration curves were constructed from 0 to 100pgμL(-1) and all of them showed good linearity (r(2)>0.99). The limit of quantification was from 2.5 to 5pg injected into the column. The method recoveries calculated using spiked mouse liver and spiked mouse muscle were between 83% and 118% (except T1 and rT2 at high concentration) with a coefficient of variation (CV) of <10% for all derivatives. The new methodology allows us to measure T4 and T3 concentrations in a range from 21 to about 100mg and give a more extensive insight on thyroid hormone concentration in different mouse tissue.
AU  - de Angelis, M.
AU  - Giesert, F.
AU  - Finan, B.
AU  - Clemmensen, C.
AU  - Müller, T.D.
AU  - Vogt Weisenhorn, D.M.
AU  - Tschöp, M.H.
AU  - Schramm, K.-W.
C1  - 49525
C2  - 40764
CY  - Amsterdam
SP  - 413-420
TI  - Determination of thyroid hormones in mouse tissues by isotope-dilution microflow liquid chromatography-mass spectrometry method.
JO  - J. Chromatogr. B
VL  - 1033-1034
PB  - Elsevier Science Bv
PY  - 2016
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - In systems biology, the combination of multiple types of omics data, such as metabolomics, proteomics, transcriptomics, and genomics, yields more information on a biological process than the analysis of a single type of data. Thus, data from different omics platforms is usually combined in one experimental setup to obtain insight into a biological process or a disease state. Particularly high accuracy metabolomics data from modern mass spectrometry instruments is currently more and more integrated into biological studies. Reflecting this trend, we extended InCroMAP, a data integration, analysis and visualization tool for genomics, transcriptomics, and proteomics data. Now, the tool is able to perform an integrated enrichment analysis and pathway-based visualization of multi-omics data and thus, it is suitable for the evaluation of comprehensive systems biology studies.
AU  - Eichner, J.*
AU  - Rosenbaum, L.*
AU  - Wrzodek, C.*
AU  - Häring, H.-U.
AU  - Zell, A.*
AU  - Lehmann, R.
C1  - 31245
C2  - 34254
CY  - Amsterdam
SP  - 77-82
TI  - Integrated enrichment analysis and pathway-centered visualization of metabolomics, proteomics, transcriptomics, and genomics data by using the InCroMAP software.
JO  - J. Chromatogr. B
VL  - 966
PB  - Elsevier Science Bv
PY  - 2014
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - Separation of isomeric molecular species, e.g. double bond position isomers, is a challenging task for liquid chromatography. The two steroid hormones Δ4- and Δ7-dafachronic acid (DA) represent such an isomeric pair. DAs are 3-ketosteroids found in the nematode Caenorhabditis elegans and generated from cholesterol. Δ4- and Δ7-DA have important biological activities and are produced by two different biological pathways in C. elegans. Here we have described a fast separation method for these two isomers using a 1.3μm core-shell particle in less than 10min together with a simple MeOH extraction. Using this method we were able to independently quantify Δ4- and Δ7-DA in C. elegans independently from each other and limits of detection of about 5ng/ml for each isomer were achieved with a good day-to-day reproducibility. As proof-of-principle the method has been applied to the quantification of DAs in worms fed ad libitum or under bacterial deprivation.
AU  - Witting, M.
AU  - Rudloff, H.-C.
AU  - Thondamal, M.*
AU  - Aguilaniu, H.*
AU  - Schmitt-Kopplin, P.
C1  - 43028
C2  - 35981
CY  - Amsterdam
SP  - 118-121
TI  - Fast separation and quantification of steroid hormones Δ4- and Δ7-dafachronic acid in Caenorhabditis elegans.
JO  - J. Chromatogr. B
VL  - 978-979
PB  - Elsevier Science Bv
PY  - 2014
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - In a non-hypothesis driven metabolomics approach plasma samples collected at six different time points (before, during and after an exercise bout) were analyzed by gas chromatography-time of flight mass spectrometry (GC-TOF MS). Since independent component analysis (ICA) does not need a priori information on the investigated process and moreover can separate statistically independent source signals with non-Gaussian distribution, we aimed to elucidate the analytical power of ICA for the metabolic pattern analysis and the identification of key metabolites in this exercise study. A novel approach based on descriptive statistics was established to optimize ICA model. In the GC-TOF MS data set the number of principal components after whitening and the number of independent components of ICA were optimized and systematically selected by descriptive statistics. The elucidated dominating independent components were involved in fuel metabolism, representing one of the most affected metabolic changes occurring in exercising humans. Conclusive time dependent physiological changes of the metabolic pattern under exercise conditions were detected. We conclude that after optimization ICA can successfully elucidate key metabolite pattern as well as characteristic metabolites in metabolic processes thereby simplifying the explanation of complex biological processes. Moreover. ICA is capable to study time series in complex experiments with multi-levels and multi-factors.
AU  - Li, X.*
AU  - Hansen, J.*
AU  - Zhao, X.J.*
AU  - Lu, X.*
AU  - Weigert, C.
AU  - Häring, H.-U.
AU  - Pedersen, B.K.*
AU  - Plomgaard, P.*
AU  - Lehmann, R.
AU  - Xu, G.W.*
C1  - 11647
C2  - 30732
SP  - 156-162
TI  - Independent component analysis in non-hypothesis driven metabolomics: Improvement of pattern discovery and simplification of biological data interpretation demonstrated with plasma samples of exercising humans.
JO  - J. Chromatogr. B
VL  - 910
PB  - Elsevier
PY  - 2012
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - This paper reports an LC-MS/MS method with positive electrospray ionization for the screening of commonly prescribed cardiovascular drugs in human plasma, including compounds with antihypertensive (57), antidiabetic (12), hypolipemiant (5), anticoagulant (2) and platelet anti-aggregation (2) effects. Sample treatment consisted of a simple protein precipitation with MeOH/0.1 M ZnSO₄ (4:1, v/v) solution after the addition of internal standard, followed by evaporation and reconstitution. Analytes separation was performed on a Polar-RP column (150 m x 2 mm, 4 μm) using a gradient elution of 15 min. The MS system was operated in MRM mode, monitoring one quantitation and one confirmation transition for each analyte. The recovery of the protein precipitation step ranged from 50 to 70% for most of the compounds, while some were considerably affected by matrix effects. Since several analytes fulfilled the linearity, accuracy and precision values required by the ICH guidelines, the method proved to be suitable for their quantitative analysis. The limits of quantitation varied from 0.38 to 9.1 μg/L and the limits of detection from 0.12 to 5.34 μg/L. The method showed to be suitable for the detection of plasma samples of patients under cardiovascular treatment with the studied drugs, and for 55 compounds reliable quantitative results could be obtained.
AU  - Gonzalez, O.*
AU  - Alonso, R.M.*
AU  - Ferreiros, N.*
AU  - Weinmann, W.*
AU  - Zimmermann, R.
AU  - Dresen, S.*
C1  - 4839
C2  - 28659
SP  - 243-252
TI  - Development of an LC-MS/MS method for the quantitation of 55 compounds prescribed in combined cardiovascular therapy.
JO  - J. Chromatogr. B
VL  - 879
IS  - 3-4
PB  - Elsevier
PY  - 2011
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - A sensitive and specific liquid chromatography-tandem mass spectrometry method was developed and validated for the quantification of erucylphosphohomocholine (erufosine, ErPC(3)) in pharmacokinetic studies. Nine-fold deuterated ErPC(3) was used as the internal standard. Following protein precipitation, reversed phase chromatography was performed. For analyte detection, electrospray ionization in the positive mode was applied. The mass transition m/z 504.4>139.1 was recorded for ErPC(3), and the transition m/z 513.7>139.1 for the internal standard, respectively. Good linearity with a correlation coefficient >0.99 was found for the range of 0.48-15 mg/L ErPC(3) in plasma (0.93-29.8 microM), the important range for clinical pharmacokinetic analysis. Interassay coefficients (n=10) of variation between 4.2% and 5.5% were found for ErPC(3) pool samples with concentrations between 4.7 mg/L and 44.0mg/L, respectively. The method has been used for analyses during a phase I clinical trial of ErPC(3).
AU  - Lindner, L.H.
AU  - Eibl, H.*
AU  - Hossann, M.
AU  - Vogeser, M.*
C1  - 1889
C2  - 25432
SP  - 16-19
TI  - Quantification of erufosine, the first intravenously applicable alkylphosphocholine, in human plasma by isotope dilution liquid chromatography-tandem mass spectrometry using a deuterated internal standard.
JO  - J. Chromatogr. B
VL  - 869
IS  - 1-2
PB  - Elsevier
PY  - 2008
SN  - 1570-0232
ER  - 

TY  - JOUR
AU  - Rios-Blanco, M.N.*
AU  - Ranasinghe, A.*
AU  - Upton, P.*
AU  - Lee, M.S.
AU  - Filser, J.G.
AU  - Swenberg, J.A.*
C1  - 22019
C2  - 20572
SP  - 383-391
TI  - Exposure-dependent accumulation of N-(2-hydroxypropyl)valine in hemoglobin of F344 rats exposed to propylene oxide by the inhalation route.
JO  - J. Chromatogr. B
VL  - 778
PY  - 2002
SN  - 1570-0232
ER  - 

TY  - JOUR
AU  - Schramel, P.
C1  - 10093
C2  - 20666
SP  - 275-278
TI  - Determination of 235U and 238U in urine samples using sector field inductively coupled plasma mass spectrometry.
JO  - J. Chromatogr. B
VL  - 778
PY  - 2002
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - Equations to describe the two sites binding between proteins and ligands were deduced. According to these equations, not only the binding constants, but also the mole fraction of proteins in different forms could be obtained. Using the published data on the interaction between human serum albumin (HSA) and three kinds of porphyrin (coproporphyrin (CP), uroporphyrin I (UP) and protoporphyrin (PP)), a further study on their binding was carried out. It was concluded that there may exist two binding sites with the binding constants at the first site. proved to be the preferential one, being 6.50 x 10(5) 1.94 x 10(6) and 8.94 x 10(5). respectively. In addition. it was also demonstrated that the two binding sites of HSA with CP and UP might be of different kinds, though those of HSA and PP were of the same kind but at different positions.
AU  - Zhang, W.*
AU  - Zhang, L.*
AU  - Ping, G.*
AU  - Zhang, Y.*
AU  - Kettrup, A.
C1  - 10092
C2  - 20387
SP  - 211-214
TI  - Study on the multiple sites binding of human serum albumin and porphyrin by affinity capillary electrophoresis.
JO  - J. Chromatogr. B
VL  - 768
PB  - Elsevier
PY  - 2002
SN  - 1570-0232
ER  - 

TY  - JOUR
AU  - Ring, J.*
AU  - Brockow, K.*
AU  - Behrendt, H.
C1  - 21852
C2  - 20070
SP  - 3-10
TI  - Adverse reactions to foods.
JO  - J. Chromatogr. B
VL  - 756
PY  - 2001
SN  - 1570-0232
ER  - 

TY  - JOUR
AU  - Lebuhn, M.
AU  - Hartmann, A.
C1  - 20061
C2  - 13234
SP  - 255-266
TI  - A method for the determination of indole-3-acetic acid and related compounds of L-tryptophan catabolism in soils.
JO  - J. Chromatogr. B
VL  - 629
PY  - 1993
SN  - 1570-0232
ER  - 

TY  - JOUR
AB  - A simple capillary gas chromatographic method is described for direct determination of styrene-7,8-oxide (styrene oxide) in blood samples of 1 ml, with a detection limit of 1 ng/ml. After the addition of 1-phenylpropylene oxide as internal standard, blood samples were extracted with n-hexane, the n-hexane phases were concentrated under nitrogen, and up to 25 μl of the resulting solution were injected on-column using a retention gap. Separation was carried out on a fused-silica capillary column coupled to a flame ionization detector. Using this method the metabolism of styrene oxide in rat blood was investigated. Concentrations of styrene oxide in the blood of rats exposed to styrene at atmospheric concentrations between 20 and 800 ppm for 3 h at steady-state conditions are reported.
AU  - Kessler, W.
AU  - Jiang, X.
AU  - Filser, J.G.
C1  - 42627
C2  - 40233
SP  - 67-75
TI  - Direct determination of styrene-7,8-oxide in blood by gas chromatography with flame ionization detection.
JO  - J. Chromatogr. B
VL  - 534
IS  - C
PY  - 1990
SN  - 1570-0232
ER  - 

TY  - JOUR
AU  - Maier, K.L.
AU  - Costabel, U.
AU  - Lenz, A.-G.
AU  - Leuschel, L.
C1  - 17759
C2  - 10666
SP  - 380-387
TI  - Simultaneous Determination of L-homoserine and L-homoserine Lactone by Reversed-phase Liquid Chromatography in Acid Hydrolysates of Proteins After Cyanogen Bromide Treatment.
JO  - J. Chromatogr. B
VL  - 493
PY  - 1989
SN  - 1570-0232
ER  -