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Ionisation Mass Spectrometry (ionisation + mass_spectrometry)
Kinds of Ionisation Mass Spectrometry Selected AbstractsDetermination of Lithium Contents in Silicates by Isotope Dilution ICP-MS and its Evaluation by Isotope Dilution Thermal Ionisation Mass SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 3 2004Takuya Moriguti Lithium; ICP-MS avec dilution isotopique; TIMS; matériaux silicatés de référence; météorites A precise and simple method for the determination of lithium concentrations in small amounts of silicate sample was developed by applying isotope dilution-inductively coupled plasma-mass spectrometry (ID-ICP-MS). Samples plus a Li spike were digested with HF-HClO4, dried and diluted with HNO3, and measured by ICP-MS. No matrix effects were observed for 7Li/6Li in rock solutions with a dilution factor (DF) of 97 at an ICP power of 1.7 kW. By this method, the determination of 0.5 ,g g -1 Li in a silicate sample of 1 mg can be made with a blank correction of < 1%. Lithium contents of ultrabasic to acidic silicate reference materials (JP-1, JB-2, JB-3, JA-1, JA-2, JA-3, JR-1 and JR-2 from the Geological Survey of Japan, and PCC-1 from the US Geological Survey) and chondrites (three different Allende and one Murchison sample) of 8 to 81 mg were determined. The relative standard deviation (RSD) was typically < 1.7%. Lithium contents of these samples were further determined by isotope dilution-thermal ionisation mass spectrometry (ID-TIMS). The relative differences between ID-ICP-MS and ID-TIMS were typically < 2%, indicating the high accuracy of ID-ICP-MS developed in this study. Nous avons développé une méthode simple et précise de détermination des concentrations en lithium dans de très petits échantillons silicatés. Elle est basée sur la méthode de dilution isotopique couplée à l'analyse par spectrométrie de masse avec couplage induit (ID-ICP-MS). Les échantillons auxquels est ajouté le spike de Li, sont mis en solution avec un mélange HF-HclO4, évaporés à sec, puis repris avec HNO3 et analysés à l'ICP-MS. Aucun effet de matrice n'est observé sur les rapports 7Li/6Li dans les solutions quand les facteurs de dilution sont 97 et qu'elles sont analysées avec une puissance du plasma de 1.7 kW. Par cette méthode, la détermination de 0.5 ,g g -1 de Li dans un échantillon silicaté de 1 mg peut être effectuée avec une correction de blanc < 1 %. Les teneurs en lithium des matériaux de référence de composition ultrabasique à acide (JP-1, JB-2, JB-3, JA-1, JA-2, JA-3, JR- 1 et JR-2 du Service Géologique du Japon, et PCC-1 du Service Géologique des USA) et de chondrites (trois échantillons différents d'Allende et un de Murchison), de poids variant entre 8 et 81 mg ont été déterminées. La déviation standard relative typique était < 1.7%. Les teneurs en lithium de ces échantillons ont été ensuite mesurées par dilution isotopique et spectrométrie de masse à thermo-ionisation (ID-TIMS). Les différences entre les résultats obtenus par ID-ICP-MS et ID-TIMS étaient < 2%, démontrant ainsi la grande justesse de la technique ID-ICP-MS développée dans cette étude. [source] Molybdenum Concentrations Measured in Eleven USGS Geochemical Reference Materials by Isotope Dilution Thermal Ionisation Mass SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2 2000Michael E. Wieser molybdène; dilution isotopique; spectrométrie de masse à; thermo-ionisation; matériaux de référence USGS Molybdenum concentrations in eleven USGS geochemical reference materials AGV-1, BCR-1, BHVO-1, BIR-1, DNC-1, DTS-1, G-2, GSP-1, MAG-1, PCC-1 and W-2 were measured by isotope dilution thermal ionisation mass spectrometry (ID-TIMS). In every case but one, the concentrations determined in this study were significantly lower than the current consensus values. Molybdenum concentrations determined by ID-TIMS are inherently more accurate and precisions may be up to an order of magnitude higher than those measured by other analytical techniques. Les concentrations en molybdène de onze matériaux géochimiques de référence de l'USGS, AGV-1, BCR-1, BHVO-1, BIR-1, DNC-1, DTS-1, G-2, GSP-1, MAG-1, PCC-1 et W-2, ont été mesurées par dilution isotopique et spectrométrie de masse à thermo-ionisation (ID-TIMS). Dans tous les cas sauf un, les concentrations déterminées dans cette étude sont nettement inférieures aux valeurs généralement admises. Les concentrations en molybdène déterminées par ID-TIMS sont par définition plus exactes et leur précision analytique peut tre améliorée d'un ordre de grandeur par rapport à celle déterminée par d'autres techniques analytiques. [source] A generic approach to the impurity profiling of drugs using standardised and independent capillary zone electrophoresis methods coupled to electrospray ionisation mass spectrometryELECTROPHORESIS, Issue 9 2005Aurélie Vassort Abstract Three standardised, capillary zone electrophoresis-electrospray ionisation mass spectrometry (CZE-ESI-MS) methods were developed for the analysis of six drug candidates and their respective process-related impurities comprising a total of 22 analytes with a range of functional groups and lipophilicities. The selected backround electrolyte conditions were found to be: 60/40 v/v 10 mM ammonium formate pH 3.5/organic, 60/40 v/v 10 mM ammonium acetate pH 7.0/organic and 10 mM piperidine, pH 10.5, where the organic solvent is 50/50 v/v methanol/acetonitrile. The coaxial sheath flow consisted of either 0.1% v/v formic acid in 50/50 v/v methanol/water, or 10 mM ammonium acetate in 50/50 v/v methanol/water, depending on the mixture being analysed. Factor analysis and informational theory were used to quantify the orthogonality of the methods and predict their complementarities. The three selected CZE-ESI-MS methods allowed the identification of 21 out of 22 of all the drug candidates and their process-related impurities and provided orthogonality with four established high-performance liquid chromatography-mass spectrometry (HPLC-MS) methods. These methodologies therefore form the basis of a generic approach to impurity profiling of pharmaceutical drug candidates and can be applied with little or no analytical method development, thereby offering significant resource and time savings. [source] The First Sandwich Complex with an Octa(thioether) Coordination Sphere: Bis(maleonitrile-tetrathia-12-crown-4)silver(I),EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2006Hans-Jürgen Holdt Abstract The new tetrathiacrown ethers maleonitrile-tetrathia-12-crown-4 (mn12S4) and maleonitrile-tetrathia-13-crown-4 (mn13S4) have been prepared and characterised by X-ray crystallographic analysis. These crown ethers form 2:1, 3:2 and 1:1 complexes with AgY (Y = BF4, PF6). The crystal structures of [Ag(mn12S4)2]BF4 (3a), [Ag(mn13S4)2]BF4 (4a) and [Ag2(mn13S4)3](PF6)2 (6b) have been determined. Compound 3a contains the centrosymmetric sandwich complex cation [Ag(mn12S4)2]+ where each mn12S4 ligand is coordinated to the Ag centre in an endo manner through all four S atoms. The 2:1 complex [Ag(mn12S4)2]+ is the first sandwich complex with a tetrathiacrown ether and the first complex with an octa(thioether) coordination sphere. The crystal structure of compound 4a also reveals a 2:1 complex. This complex, [Ag(mn13S4)2]+, exhibits a half-sandwich structure. One mn13S4 ligand coordinates to Ag+ by all four S donor atoms and the other 13S4 crown by only one S atom. Compound 6b contains a dinuclear Ag complex. The Ag complexes 3a,b,8a,b were also studied by electrospray ionisation mass spectrometry. Collision-induced dissociation (CID) was used to compare the relative stability of 2:1 complexes [AgL2]+ and 1:1 complexes [AgL]+ (L = mn12S4, mn13S4). The 13C NMR chemical shifts of 2:1 and 1:1 Ag complexes and their corresponding free ligands were also estimated and compared. The free energy of the barrier of ring inversion (,G,) for [Ag(mn12S4)2]+ was determined to be 64 kJ,mol,1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Kinetic and Thermodynamic Studies of the Disproportionation of Hydrogen Peroxide by Dimanganese(ii,ii) and -(ii,iii) Complexes of a Bridging Phenolate LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2005Lionel Dubois Abstract The dimanganese(ii,ii) complexes [Mn2(L)(OAc)2(CH3OH)]-(ClO4) (1a) and [Mn2(L)(OBz)2(H2O)](ClO4) (1b) as well as the dimanganese(ii,iii) complex [Mn2(L)(OAc)2(CH3OH)]-(ClO4)2 (2a), where HL is the asymmetric phenol ligand2-[bis(2-pyridylmethyl)aminomethyl]-6-{[(benzyl)(2-pyridyl-methyl)amino]methyl}-4-methylphenol, react with hydrogen peroxide in acetonitrile solution. The initial reaction rates and their temperature and acid/base dependencies were investigated by monitoring the dioxygen evolution. These studies revealed a first-order dependence on both the catalyst and H2O2 and a strong influence of the carboxylate. Electrospray ionisation mass spectrometry as well as EPR and UV/Vis spectroscopy were used to monitor the reaction catalysed by 2a. The same bis(,-oxo)dimanganese(III,IV) and (,-oxo)dimanganese(ii,iii) active species as found for 1a were detected in the catalytic medium. The EPR spectra recorded during the catalase-like reaction revealed the accumulation of the magnetically uncoupled dimanganese(ii,iii) precursor of the active bis(,-oxo)dimanganese(III,IV) species which dominates the spectra in the case of 1a. This difference can be attributed to the different pH conditions generated by the reaction and reflects differences in the initiation phases for the two catalysts. Overall, the kinetic and thermodynamic studies of H2O2 disproportionation by these dimanganese complexes are fully consistent with the mechanism deduced from our previous extensive spectroscopic studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Determination of Lithium Contents in Silicates by Isotope Dilution ICP-MS and its Evaluation by Isotope Dilution Thermal Ionisation Mass SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 3 2004Takuya Moriguti Lithium; ICP-MS avec dilution isotopique; TIMS; matériaux silicatés de référence; météorites A precise and simple method for the determination of lithium concentrations in small amounts of silicate sample was developed by applying isotope dilution-inductively coupled plasma-mass spectrometry (ID-ICP-MS). Samples plus a Li spike were digested with HF-HClO4, dried and diluted with HNO3, and measured by ICP-MS. No matrix effects were observed for 7Li/6Li in rock solutions with a dilution factor (DF) of 97 at an ICP power of 1.7 kW. By this method, the determination of 0.5 ,g g -1 Li in a silicate sample of 1 mg can be made with a blank correction of < 1%. Lithium contents of ultrabasic to acidic silicate reference materials (JP-1, JB-2, JB-3, JA-1, JA-2, JA-3, JR-1 and JR-2 from the Geological Survey of Japan, and PCC-1 from the US Geological Survey) and chondrites (three different Allende and one Murchison sample) of 8 to 81 mg were determined. The relative standard deviation (RSD) was typically < 1.7%. Lithium contents of these samples were further determined by isotope dilution-thermal ionisation mass spectrometry (ID-TIMS). The relative differences between ID-ICP-MS and ID-TIMS were typically < 2%, indicating the high accuracy of ID-ICP-MS developed in this study. Nous avons développé une méthode simple et précise de détermination des concentrations en lithium dans de très petits échantillons silicatés. Elle est basée sur la méthode de dilution isotopique couplée à l'analyse par spectrométrie de masse avec couplage induit (ID-ICP-MS). Les échantillons auxquels est ajouté le spike de Li, sont mis en solution avec un mélange HF-HclO4, évaporés à sec, puis repris avec HNO3 et analysés à l'ICP-MS. Aucun effet de matrice n'est observé sur les rapports 7Li/6Li dans les solutions quand les facteurs de dilution sont 97 et qu'elles sont analysées avec une puissance du plasma de 1.7 kW. Par cette méthode, la détermination de 0.5 ,g g -1 de Li dans un échantillon silicaté de 1 mg peut être effectuée avec une correction de blanc < 1 %. Les teneurs en lithium des matériaux de référence de composition ultrabasique à acide (JP-1, JB-2, JB-3, JA-1, JA-2, JA-3, JR- 1 et JR-2 du Service Géologique du Japon, et PCC-1 du Service Géologique des USA) et de chondrites (trois échantillons différents d'Allende et un de Murchison), de poids variant entre 8 et 81 mg ont été déterminées. La déviation standard relative typique était < 1.7%. Les teneurs en lithium de ces échantillons ont été ensuite mesurées par dilution isotopique et spectrométrie de masse à thermo-ionisation (ID-TIMS). Les différences entre les résultats obtenus par ID-ICP-MS et ID-TIMS étaient < 2%, démontrant ainsi la grande justesse de la technique ID-ICP-MS développée dans cette étude. [source] Molybdenum Concentrations Measured in Eleven USGS Geochemical Reference Materials by Isotope Dilution Thermal Ionisation Mass SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2 2000Michael E. Wieser molybdène; dilution isotopique; spectrométrie de masse à; thermo-ionisation; matériaux de référence USGS Molybdenum concentrations in eleven USGS geochemical reference materials AGV-1, BCR-1, BHVO-1, BIR-1, DNC-1, DTS-1, G-2, GSP-1, MAG-1, PCC-1 and W-2 were measured by isotope dilution thermal ionisation mass spectrometry (ID-TIMS). In every case but one, the concentrations determined in this study were significantly lower than the current consensus values. Molybdenum concentrations determined by ID-TIMS are inherently more accurate and precisions may be up to an order of magnitude higher than those measured by other analytical techniques. Les concentrations en molybdène de onze matériaux géochimiques de référence de l'USGS, AGV-1, BCR-1, BHVO-1, BIR-1, DNC-1, DTS-1, G-2, GSP-1, MAG-1, PCC-1 et W-2, ont été mesurées par dilution isotopique et spectrométrie de masse à thermo-ionisation (ID-TIMS). Dans tous les cas sauf un, les concentrations déterminées dans cette étude sont nettement inférieures aux valeurs généralement admises. Les concentrations en molybdène déterminées par ID-TIMS sont par définition plus exactes et leur précision analytique peut tre améliorée d'un ordre de grandeur par rapport à celle déterminée par d'autres techniques analytiques. [source] A kinetic study of the reactions of (+)-catechin with aldehydes derived from toasted oakJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2007Marie-Françoise Nonier Abstract The reactions between (+)-catechin and representative oak wood furanic (furfuraldehyde, 5-hydroxymethylfurfuraldehyde and 5-methylfurfuraldehyde) and phenolic (vanillin and syringaldehyde) aldehydes in a wine-like model solution were studied and the corresponding condensation kinetics at pH 3.0 and 3.5 were compared. A comparative study on the reactivity of these two representative families of aldehydes towards (+)-catechin showed a large difference between them. When incubated separately with (+)-catechin at both pH values, the reactions were faster with furanic aldehydes than with phenolic aldehydes. In mixtures containing (+)-catechin and individual aldehydes, new compounds were identified by high-performance liquid chromatography (HPLC)/UV,visible detection, some of which were characterised by liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS). The increase in solution absorbance with time was closely linked to these new products. Copyright © 2007 Society of Chemical Industry [source] Comparative study of six pear cultivars in terms of their phenolic and vitamin C contents and antioxidant capacityJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2003Andrea C Galvis Sánchez Abstract The main phenolic compounds in six pear cultivars were identified and quantified using high-performance liquid chromatography/diode array detection (HPLC/DAD) and HPLC/electrospray ionisation mass spectrometry (HPLC/ESIMS). Major quantitative differences were found in the phenolic profiles. The peel contained higher concentrations of chlorogenic acid, flavonols and arbutin than the flesh, where only chlorogenic acid was detected. Total phenolics ranged from 1235 to 2005 mg kg,1 in the peel and from 28 to 81 mg k g,1 in the flesh. Ascorbic acid and dehydroascorbic acid were detected in the peel, whereas only dehydroascorbic acid was present in the flesh. The ranges of vitamin C content were from 116 to 228 mg kg,1 in the peel and from 28 to 53 mg kg,1 in the flesh. The antioxidant capacity was correlated with the content of chlorogenic acid (r = 0.46), while ascorbic acid made only a small contribution to the total antioxidant capacity of the fruit. Copyright © 2003 Society of Chemical Industry [source] A rapid ultra-performance liquid chromatography,electrospray Ionisation mass spectrometric method for the analysis of saponins in the adventitious roots of Panax notoginsengPHYTOCHEMICAL ANALYSIS, Issue 1 2009Mo Dan Abstract Introduction Saponins are bioactive compounds employed in the prevention and treatment of cardiovascular and cerebrovascular diseases. The adventitious roots of Panax notoginseng may offer an alternative source of saponins. Identification and determination of saponins in the crude extract is challenging owing to their similar structures and the lack of standards. Objective To develop a rapid, sensitive and accurate method based on solid-phase extraction followed by ultra-performance liquid chromatography,electrospray ionisation mass spectrometry (UPLC-ESI-MS) for the identification and quantification of saponins in P. notoginseng. Methodology Following extraction using Waters OasisTM HLB cartridges, the analytes were subjected to a UPLC system with a Waters Acquity BEH C18 chromatographic column and a binary mobile phase system consisting of 0.05% formic acid in water and acetonitrile under gradient elution conditions, with final detection by ESI-MS in the positive ion mode. Results The UPLC-ESI-MS method gave limits of detection and quantification within the range 0.015,0.382 and 0.052,1.124 µg/mL, respectively, for 15 studied saponins. The instrumentation/injection precision (RSD) was 4.5% for a low concentration and 3.2% for an intermediate concentration sample. The intra- and inter-day repeatability was less than 2.65% (RSD). The method described was validated using spiked samples with different amounts of saponin standards. Conclusion This UPLC-ESI-MS assay provides a suitable quality control method for the tentative identification and determination of major biological active constituents in adventitious and native roots of P. notoginseng. Copyright © 2008 John Wiley & Sons, Ltd. [source] Characterisation of fungal lanostane-type triterpene acids by electrospray ionisation mass spectrometryPHYTOCHEMICAL ANALYSIS, Issue 6 2007Gabriela M. Cabrera Abstract Lanostane-triterpene acids obtained from the culture of the fungus Coriolellus malicola were studied by electrospray mass spectrometry in the negative ion mode using quadrupole time-of-flight and quadrupole ion trap analysers. Despite the differences observed in the mass spectra recorded with these instruments, a set of fragment ions was found to be characteristic of the family, depending on the ,7,9(11) or ,8 skeleton and the particular functional group at C-3. Copyright © 2007 John Wiley & Sons, Ltd. [source] Reversed-phase HPLC-ESI/MS analysis of birch leaf proanthocyanidins after their acidic degradation in the presence of nucleophilesPHYTOCHEMICAL ANALYSIS, Issue 5 2007Maarit Karonen Abstract Mountain birch leaves contain large amounts of structurally variable polymeric proanthocyanidins. Their isolation procedure was enhanced by the addition of liquid,liquid extractions prior to column chromatography over Sephadex LH-20. Isolated polymeric proanthocyanidins were depolymerised by acid-catalysis in the presence of benzyl mercaptan or phloroglucinol in order to study their composition. The resulting degradation products, flavan-3-ols and flavan-3-ol adducts, were analysed with reversed-phase high-performance liquid chromatography using UV photodiode array detection for quantification and electrospray ionisation mass spectrometry for identification. The results showed that polymeric proanthocyanidins contained (epi)gallocatechins and (epi)catechins as the extension units and, mainly, (+)-catechin as the terminal unit. The mean degree of polymerisation was found to be 26 based on thiolysis and 31 based on phloroglucinol degradation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Detecting equilibrium cytochrome c folding intermediates by electrospray ionisation mass spectrometry: Two partially folded forms populate the molten-globule statePROTEIN SCIENCE, Issue 3 2002Rita Grandori Abstract Nanoelectrospray ionization mass spectrometry (nano-ESI-MS) is applied to the characterization of ferric cytochromec (cytc) conformational states under different solvent conditions. The methanol-induced molten-globule state in the pH range 2.6,3.0 is found to be populated by two distinct, partially folded conformers IA and IB. The more compact intermediate IB resembles that induced by glycerol in acid-unfolded cytc. The less compact one, IA, also can be induced by destabilization of the native structure by trifluoroethanol. IA and IB can be detected, in the absence of additives, around the midpoint of the acid-induced unfolding transition, providing direct evidence for involvement of equilibrium folding intermediates in cytc conformational transitions at low pH. This study shows that mass spectrometry can contribute to the characterization of molten-globule states of proteins by detection of distinct, although poorly populated, conformations involved in a dynamic equilibrium. [source] Characterisation of oxazepam degradation products by high-performance liquid chromatography/electrospray ionisation mass spectrometry and electrospray ionisation quadrupole time-of-flight tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2010Thomas J. P. Smyth Oxazepam has been subjected to controlled degradation at 100°C for 3,h in 0.5,M HCl and 0.5,M NaOH. Following neutralisation of the degradation mixture and removal of salts by solid-phase extraction (SPE), isocratic high-performance liquid chromatography/mass spectrometry (HPLC/MS) using water/methanol (25:75,v/v) as the mobile phase was carried out using a flow diverter to collect fractions prior to their characterisation by electrospray ionisation multi-stage mass spectrometry (ESI-MSn) and proposal of the corresponding fragmentation patterns. The elemental compositions of the degradation products and their MS fragments were evaluated using electrospray ionisation quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) which was then used to support the proposed fragmentation patterns. Copyright © 2010 John Wiley & Sons, Ltd. [source] Fragmentation pathways of 2,3-dimethyl-2,3-dinitrobutane cations in the gas phaseRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2009Martin R. L. Paine 2,3-Dimethyl-2,3-dinitrobutane (DMNB) is an explosive taggant added to plastic explosives during manufacture making them more susceptible to vapour-phase detection systems. In this study, the formation and detection of gas-phase [M+H]+, [M+Li]+, [M+NH4]+ and [M+Na]+ adducts of DMNB was achieved using electrospray ionisation on a triple quadrupole mass spectrometer. The [M+H]+ ion abundance was found to have a strong dependence on ion source temperature, decreasing markedly at source temperatures above 50°C. In contrast, the [M+Na]+ ion demonstrated increasing ion abundance at source temperatures up to 105°C. The relative susceptibility of DMNB adduct ions toward dissociation was investigated by collision-induced dissociation. Probable structures of product ions and mechanisms for unimolecular dissociation have been inferred based on fragmentation patterns from tandem mass (MS/MS) spectra of source-formed ions of normal and isotopically labelled DMNB, and quantum chemical calculations. Both thermal and collisional activation studies suggest that the [M+Na]+ adduct ions are significantly more stable toward dissociation than their protonated analogues and, as a consequence, the former provide attractive targets for detection by contemporary rapid screening methods such as desorption electrospray ionisation mass spectrometry. Copyright © 2009 Commonwealth of Australia. Published by John Wiley & Sons, Ltd. [source] Identification and quantitation of phenolic compounds in faecal matrix by capillary gas chromatography and nano-electrospray mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2006Ulrike Knust Very few relevant methods have been described for the detection and quantitation of phenolic compounds in faecal matrix. Extraction with conventional organic solvents such as chloroform/methanol (2:1, Folch reagent), methanol and ethanol (72%) showed high extraction efficiency for lipids and also gave good recovery of the major phenolic compounds present in the matrix. However, in comparison with a newly developed phosphate buffer method, the yield of minor phenolics was negligible when detected by these conventional methods. Conventional methods also lead to contamination of the ion source of the mass spectrometer and rapid deterioration of column performance mostly due to the high concentration of lipids. However, if the faecal matrix is initially extracted with phosphate buffer, and the extract acidified and re-extracted with diethyl ether, the range and yield of phenolic compounds are enhanced and the problem of lipid contamination is substantially alleviated. Following pilot studies and optimisation of the procedure, individual phenolic compounds (n,=,29) were identified by nano-electrospray ionisation mass spectrometry (nano-ESI-MS), nano-ESI-tandem mass spectrometry (MS/MS) and gas chromatography/mass spectrometry (GC/EI-MS) and quantitated (n,=,27) by GC/MS in subsets (n,=,5) of faecal samples, collected during the European Agency for Cancer Prevention calcium/fibre intervention study from four European countries (Italy, Germany, Spain and Denmark). A range of phenolic compounds (mainly acids) was detected, dominated by phenylacetic, benzoic, phenylpropionic and m -hydroxyphenylpropionic acids, representing on average 9.91 (93%), 8.25 (92%), 9.45 (95%) and 11.05 (98%) mM in the Italian, German, Spanish and Danish samples, respectively. The new method should enable large epidemiologic, case-control and intervention studies on the relevance of phenolic antioxidants in the aetiology of colorectal cancer to be conducted in the future. Copyright © 2006 John Wiley & Sons, Ltd. [source] Investigating the structural properties of amyloid-like fibrils formed in vitro from ,2 -microglobulin using limited proteolysis and electrospray ionisation mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2006Sarah L. Myers The protein ,2 -microglobulin (,2m) aggregates to form classical amyloid fibrils in patients undergoing long-term haemodialysis. Amyloid-like fibrils with a cross- , fold can also be formed from wild-type ,2m under acidic conditions in vitro. The morphology of such fibrils depends critically on the conditions used: incubation of ,2m in low ionic strength buffers at pH 2.5 results in the formation of long (µm), straight fibrils while, at pH 3.6, short (<500,nm) fibrils form. At higher ionic strengths (0.2,0.4,M) at pH 1.5,3.6, the fibrils have a distinct curved and nodular morphology. To determine the conformational properties of ,2m within in vitro fibrils of different morphologies, limited proteolysis of each fibril type using pepsin was performed and the resulting peptide fragments identified by tandem mass spectrometry. For comparison, the proteolytic degradation patterns of monomeric ,2m and seven synthetic peptides spanning the entire sequence of the intact protein were similarly analysed. The results show that fibrils with different morphologies result in distinct digestion patterns. While the curved, worm-like fibrils are relatively weakly protected from proteolysis, the long, straight fibrils formed at pH 2.5 at low ionic strength show only a single cut-site at Val9, demonstrating that substantial refolding of the initially acid-denatured and unprotected state of ,2m occurs during assembly. The data demonstrate that the organisation of the polypeptide chain in fibrils with different morphological features differs considerably, despite the fact that the fibrils possess a common cross- , architecture. Copyright © 2006 John Wiley & Sons, Ltd. [source] Chemical study of triterpenoid resinous materials in archaeological findings by means of direct exposure electron ionisation mass spectrometry and gas chromatography/mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2006Francesca Modugno A systematic study of standard triterpenes (, -amyrine, oleanolic acid, betulin, lupeol, betulinic acid and lupenone) and of raw resinous materials (frankincense resin, mastic resin and birch bark pitch) was performed using direct exposure electron ionisation mass spectrometry (DE-MS) and gas chromatography/mass spectrometry (GC/MS). DE-MS provides a mass spectral fingerprint of organic materials in a few minutes which highlights the compounds that are the main components in the sample. The application of principal component analysis (PCA) on DE-MS data in the mass ranges m/z 181,260 and m/z 331,500, corresponding to the fragmentation of triterpenoid molecules, enabled us to distinguish between different triterpenoid materials such as mastic resin, frankincense resin and birch bark pitch, and to graphically plot the resinous substances in three separate clusters, retaining 89% of the total variance. GC/MS analysis of the same materials has permitted us to elucidate in detail the molecular composition and to identify minor components and species that act as markers of the degradation undergone by the materials. The paper also reports the results for the organic residues contained in an Egyptian censer (5th,7th century AD) which was recovered in the excavation of the Necropolis of Antinoe (Egypt), and for the hafting material found on a Palaeolithic tool recovered at the site of Campitello (Arezzo, Tuscany), dating back to the Mid-Pleistocene period. Although DE-MS was found to be a fast analytical tool, it failed to give any information on the presence of less abundant compounds when applied to mixtures of different materials: only mastic resin was found in the residues from the Roman censer, whereas GC/MS analysis identified the presence of a vegetable oil from Brassicaceae seeds and Pinaceae resin. Birch bark pitch as a pure material was identified in the sample from the Palaeolithic flint flake using both procedures. Copyright © 2006 John Wiley & Sons, Ltd. [source] Identification of an unusual naturally occurring apolar fatty acid amide in mammalian brain and a method for its quantitative determinationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 3 2006Maurizio Dalle Carbonare Fatty acid amides (FAAs), such as the N -acylamides, N -acylethanolamides, N -acyldopamines and N -acylamino acids, are now emerging as an important new class of lipid-signalling molecules. This paper provides evidence, based on high-performance liquid chromatography/electrospray ionisation mass spectrometry (HPLC/ESI-MS/MS), gas chromatography/mass spectrometry (GC/MS) and 1H-NMR, of the occurrence in mouse and bovine brain extracts of a compound characterised by a mass spectrum attributable to a FAA not previously described, namely, the isopropyl-amide of stearic acid (SIPA). A highly sensitive GC/MS method was developed for quantification of naturally occurring SIPA and, also, for purposes of comparison, that of palmitoylethanolamide (PEA), a structurally related compound commonly determined in animal tissues. The results obtained show that SIPA levels in mouse brain are 8,10-fold higher than those of PEA. Moreover, SIPA was found in human neuroblastoma cell (SHSY-5Y) extracts, at significantly higher levels following exposure of the cells to the mitochondrial inhibitor rotenone. All this evidence not only shows surprisingly that SIPA may be found naturally in mammalian biological extracts despite the unusual functional group (i.e. isopropylamide) implicated, but also raises many important questions concerning its biological origin. Copyright © 2005 John Wiley & Sons, Ltd. [source] Characterisation of sulphoxides by atmospheric pressure ionisation mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2005Patricia Wright An observation that a series of proprietary compounds containing a methyl thiophenyl group all underwent metabolic S-oxidation, and that the product ion spectra of the resulting S-oxides showed methyl radical loss under low-energy atmospheric pressure ionisation tandem mass spectrometry (API-MS/MS) conditions, has led to an investigation of the fragmentation of commercially available sulphoxides. The phenyl methyl sulphoxides studied do lose methyl radicals under MS/MS conditions on triple quadrupole mass spectrometers. In addition, the phenyl sulphoxides, with simple substituents other than a methyl group, also showed a tendency to lose the substituent as a radical. It was concluded that radical loss from these simple sulphoxides was characteristic of S-oxidation of these molecules. Radical losses, such as those reported here, are used in-house to distinguish S-oxidation from N- and C-oxidation in metabolism studies. Copyright © 2005 John Wiley & Sons, Ltd. [source] Characterisation via electrospray ionisation multistage mass spectrometry of three related series of nitrido technetium complexes containing phosphinothiolate and dithiocarbamate ligandsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2005Michela Tubaro Nine nitrido technetium compounds comprising bis-substituted Tc(N)(PS)2 (1,4) (PS,=,bidentate phosphinothiolate ligands) and Tc(N)(dtc)2 (5, 6) derivatives (dtc,=,bidentate dithiocarbamate), and mixed-ligand Tc(N)(PS)(dtc) (7,9) species, were subjected to electrospray ionisation mass spectrometry and MSn experiments. Bis-substituted phosphinothiolato complexes 1,4 lead to the straightforward formation of dinuclear species reasonably originating from proton bound dimers. These dinuclear species do not show, under collisionally induced fragmentation processes, the formation of monomeric units but cleavages related to the ligand framework, thereby proving the high stability of the [TcH+Tc] bond. Bis-dithiocarbamate compounds 5 and 6 show, instead, abundant [M+H]+, [M+Na]+ and [2M+Na]+ ions, and their collisionally induced fragmentations are highly favoured with cleavages related to the CN and CS bonds. During these processes, the coordination of a water molecule to [MH,L]+ product ions is observed, as proved by the collisionally induced H2O loss detected for this species. Mixed-ligand compounds 7 and 8 show the protonated molecules and Na+ -cationised ions with fragmentation processes related to the dithiocarbamate moiety. This behaviour indicates that coordination of ether- and ester-substituted dithiocarbamates to the [Tc,,N] group is weaker than that of phosphinothiolates. Conversely, diethyldithiocarbamate inserted in mixed complex 9 enhances both CN and TcS bonds, and fragmentation processes suggest that metal-phosphinothiolate and metal-dithiocarbamate show comparable strength. Copyright © 2005 John Wiley & Sons, Ltd. [source] High-performance liquid chromatography with electrospray ionisation mass spectrometry and diode array detection in the identification and quantification of the degradation products of calix[4]arene crown-6 under radiolysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2004C. Lamouroux The extraction of 135Cs from high-activity liquid waste, arising from reprocessing of spent nuclear fuel, can be achieved by using calix[4]arene crown-6 compounds. The radiolytic degradation of di(n-octyloxy)calix[4]arene crown-6 (octMC6), in aliphatic or aromatic solvent in contact with 3 M nitric acid, was studied by high-performance liquid chromatography directly coupled to electrospray ionisation mass spectrometry (LC/ESI-MS). More than 50 distinct degradation products were observed, and about 30 of these were identified. These compounds can be assigned to three categories, namely, products of reactions involving radical cleavage or addition, of oxidation reactions, or of aromatic substitution reactions. The major product, corresponding to substitution by an NO2 group, was quantified by external standard calibration using a purified synthetic sample. Despite the observation of all these degradation compounds, octMC6 appears to be remarkably stable under these drastic conditions, combining hydrolysis (HNO3 3,M) and an extreme exposure to radiolysis (106,Gy). Less than 35% degradation of octMC6 was observed in aromatic solvent under these conditions. Copyright © 2004 John Wiley & Sons, Ltd. [source] Detection of phenolic oxidation products in cider apple juice by high-performance liquid chromatography electrospray ionisation ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2004S. Bernillon Juice was prepared from cider apples of the cultivar "Kermerrien" under oxidative conditions. After isolation by solid-phase extraction, the phenolic fraction was subjected to high-performance liquid chromatography/electrospray ionisation mass spectrometry. SIM scans were performed at m/z values obtained in model solutions. The oxidation products, resulting from coupling between a molecule of caffeoylquinic acid and caffeoylquinic acid, catechin or dimeric flavan-3-ol, were detected. Copyright © 2004 John Wiley & Sons, Ltd. [source] Determination of , -tocopherol in infant foods by liquid chromatography combined with atmospheric pressure chemical ionisation mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2003Andras Kalman A novel, sensitive and specific method for the quantification of , -tocopherol in two infant foods (milk and cereals) using liquid chromatography on-line with positive atmospheric pressure chemical ionisation mass spectrometry detection (LC/APCI-MS) has been developed. The samples were first saponified in order to eliminate fats and to transform tocopherol esters into free tocopherol, followed up by a liquid,liquid extraction of the analyte in petroleum benzine/diisopropyl ether (75:25, v/v) prior to injection onto the LC system. For the quantification, deuterium-labelled tocopherol was used as internal standard and the samples were monitored in selected ion monitoring (SIM) mode. Calibration curves between 1,40,,g/mL of , -tocopherol showed a good linear correlation (r2,=,0.99994), and the detection limit was determined to be 2.5,ng/mL. The within-day and between-day precision were determined for several dietetic infant formulae and certified reference samples, and found to be below 3.5%. The accuracy determined on a Nestlé reference sample (milk powder) was calculated to be 115.2,±,1.2%, which confirms the robustness of the proposed method. This study shows that single quadrupole LC/MS can be applied for the quantification of vitamins in food and the method offers better sensitivity and selectivity than traditional method such as LC-UV. This would simplify the preparation of the food samples and consequently enhance the vitamin analysis throughput in the food area. Copyright © 2003 John Wiley & Sons, Ltd. [source] Derivatisation for liquid chromatography/electrospray mass spectrometry: synthesis of pyridinium compounds and their amine and carboxylic acid derivativesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2003Samantha J. Barry A simple method has been developed for the pre-column derivatisation of low molecular weight primary and secondary amines and carboxylic acids using quaternary nitrogen compounds to enhance their detection by liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS). The synthesis of seven novel quaternary nitrogen reagents is described. The derivatives are designed to be relatively small molecules to avoid some of the steric hindrance problems that may be associated with larger derivatisation reagents. The compounds have amine and carboxylic acid functional groups with which to derivatise carboxylic acids and amines, respectively. Two of the compounds contain a bromine atom in order to assess the advantages of a bromine isotope pattern in the mass spectra. This acts as a simple marker for derivatisation and enables data processing by cluster analysis. Activation of the carboxylic acid group was achieved by the use of either 1-chloro-4-methylpyridinium iodide (CMPI) or the more reactive 1-fluoro-4-methylpyridinium p -toluenesulphonate (FMP).1 Using both of these active reagents, the degree of nucleophilic substitution was investigated for the derivatisation of a variety of small molecules. Whilst giving some increase in the ESI-MS response for the derivatised compounds, the FMP itself acted as a derivatising reagent in a competing reaction. In the light of this finding, FMP was reacted with the test compounds separately and gave positive results as a derivatising reagent. Detection of the ,pre-charged' derivatives of amines and carboxylic acids by LC/ESI-MS was investigated with respect to their ESI response and chromatography. Copyright © 2003 John Wiley & Sons, Ltd. [source] Gas chromatography/negative-ion chemical ionisation mass spectrometry for the quantitative analysis of morphine in human plasma using pentafluorobenzyl carbonate derivativesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2002H. J. Leis A sensitive and specific method for the quantitative determination of morphine in human plasma is presented. Morphine was extracted from plasma by solid phase extraction on C18 and converted to its pentafluorobenzyl carbonate trimethylsilyl derivative. The derivatives were analysed without further purification. Using gas chromatography/negative ion chemical ionisation mass spectrometry, a useful diagnostic fragment ion at m/z 356 is obtained at high relative abundance. Deuterated morphine was used as internal standard. Calibration graphs were linear within the range 1.25 to 320,nmol/L. Intra-day precision was 3.82% (15,nmol/L), 2.85% (75,nmol/L) and 4.13% (225,nmol/L), inter-day variability was found to be 1.77% (15,nmol/L), 4.95% (75,nmol/L) and 9.88% (225,nmol/L). Inter-day accuracy showed deviations of 2.18% (15,nmol/L), ,0.72% (75,nmol/L) and ,0.13% (225,nmol/L). The method is rugged and robust and has been applied to the batch analysis of morphine during pharmacokinetic profiling of the drug. Copyright © 2002 John Wiley & Sons, Ltd. [source] Rapid and sensitive quantitation of antibiotics in fermentations by electrospray mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2001Janine Morgan Electrospray ionisation mass spectrometry (ESI-MS) has been used for the determination and quantitation of a broad range of 24 antibiotics, from groups including aminoglycosides, ,-lactams, tetracyclines, antifungals and glycopeptides. Spectra have been acquired for all 24 antibiotics derived from pure samples dissolved in acetonitrile/water, along with samples extracted from complex fermentation liquor. Quantitation was carried out by the detection of the protonated molecules, using time-scheduled single-ion monitoring (SIM). ESI-MS was used to detect and quantify to 5-µM levels. A one-step extraction of antibiotics with an organic solvent (methanol) was used for this rapid and simple procedure. Specificity is not matched by other methods and antibiotic analogues (e.g. the five forms of erythromycin) can be determined within minutes. Copyright © 2001 John Wiley & Sons, Ltd. [source] A novel approach for identification and measurement of hemoglobin adducts with 1,2,3,4-diepoxybutane by liquid chromatography/electrospray ionisation mass spectrometry and matrix-assisted laser desorption/ionisation tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2001Adriana Basile The structural characterisation of the adducts formed by in vitro interaction of hemoglobin (Hb) with 1,2,3,4-diepoxybutane (DEB), the most reactive 1,3-butadiene (BD) metabolite, was obtained by liquid chromatography/electrospray ionisation mass spectrometry (LC/ES-MS) analysis of modified tryptic peptides of human hemoglobin chains. The reactive sites of human hemoglobin towards DEB and its hydroxylated derivatives (trihydroxybutyl (THB)-derivatives) were identified through the characterisation of alkylated tryptic peptides by matrix-assisted laser desorption/ionisation tandem mass spectrometry (MALDI-MS/MS). Based on this characterisation, a procedure was set up to measure the Hb-adducts of THB-derivatives by isotope dilution mass spectrometry with the use of a deuterated peptide standard. The results obtained here could permit optimisation of molecular dosimetry of BD-adducts, and extension of the analysis to the biological monitoring of occupational exposure to butadiene. Copyright © 2001 John Wiley & Sons, Ltd. [source] Electrospray ionisation mass spectrometric study of degradation products of quercetin, quercetin-3-glucoside and quercetin-3-rhamnoglucoside, produced by in vitro fermentation with human faecal floraRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2001Ulla Justesen Eight phenolic compounds, obtained by in vitro fermentation of quercetin, quercetin-3-glucoside and quercetin-3-rhamnoglucoside were analysed by electrospray ionisation mass spectrometry (ESI-MS). Low-energy collision-induced dissociation tandem mass spectrometry (CID-MS/MS) was performed on the [M,,,H], precursor ions to obtain specific fragmentation. Typical fragmentation of the phenolic acids was loss of 44 (CO2) and 18 (H2O),u. Production of m/z 108 by loss of neutral radicals, e.g. HCO2, CH3 or HCO, was also favoured. Structures of the compounds, numbered 1,8, were suggested based on the fragmentation patterns. Copyright © 2001 John Wiley & Sons, Ltd. [source] Stability of Anion Binding with Monomers of a Cationic SurfactantCHEMPHYSCHEM, Issue 6 2008Anna Jakubowska Dr. Competitive binding: Electrospray ionisation mass spectrometry is used to probe the binding ability of different anions with a cationic surfactant. Bond strengths are estimated from plots of the intensity of the peak assigned to a given complex ion in the mass spectrum versus the cone voltage applied to induce the abstraction of the counterions from the monomers (see graph). [source] | ||||||||||