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Positive Ion Mode (positive + ion_mode)
Selected AbstractsTowards a platform for the metabonomic profiling of different strains of Drosophila melanogaster using liquid chromatography,Fourier transform mass spectrometryFEBS JOURNAL, Issue 22 2009Muhammad A. Kamleh A platform based on hydrophilic interaction chromatography in combination with Fourier transform mass spectrometry was developed in order to carry out metabonomics of Drosophila melanogaster strains. The method was able to detect , 230 metabolites, mainly in the positive ion mode, after checking to eliminate false positives caused by isotope peaks, adducts and fragment ions. Two wild-type strains, Canton S and Oregon R, were studied, plus two mutant strains, Maroon Like and Chocolate. In order to observe the differential expression of metabolites, liquid chromatography-mass spectrometry analyses of the different strains were compared using sieve 1.2 software to extract metabolic differences. The output from sieve was searched against a metabolite database using an Excel-based macro written in-house. Metabolic differences were observed between the wild-type strains, and also between both Chocolate and Maroon Like compared with Oregon R. It was established that a metabonomic approach could produce results leading to the generation of new hypotheses. In addition, the structure of a new class of lipid with a histidine head group, found in all of the strains of flies, but lower in Maroon Like, was elucidated. [source] Simultaneous HPLC-DAD-MS (ESI+) determination of structural and geometrical isomers of carotenoids in mature grapes,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2010Pasquale Crupi Abstract Carotenoids are uniquely functional polyene pigments ubiquitous in nature; aside from being responsible for the color of a wide variety of vegetables, interest is being focused on food carotenoids due to their likely health benefits. From analytical point of view, it is important to unequivocally identify individual carotenoid compounds in many food stuffs. Therefore, isolation of standards from natural sources must be encouraged for accurate identifications. Like many fruits, mature grape berries contain numerous carotenoid compounds, mostly found in the skin at levels two to three times higher than in the pulp. Carotenoid compounds in a typical wine grape variety (Negroamaro) grown in Apulian region were investigated by reversed-phase C30 (RP-30) HPLC-DAD-MS (ESI+) analysis. As a consequence of an unusual ionization process of carotenoids, their mass spectra registered in the positive ion mode comprised both protonated molecules and molecular ion radicals with little fragmentation. Additionally, selective collision-induced dissociation (CID) experiments, together with fine structures of the UV,vis spectra, were used to differentiate structural and geometrical isomers. This technique allowed the simultaneous determination of regio- and cis -isomers of lutein (zeaxanthin, 9Z and 9,Z -lutein) and a cis -isomer of ,-carotene (9Z - ,-carotene), 5,6-epoxy xanthophylls (violaxanthin, (9,Z)-neoxanthin, lutein-5,6-epoxide) and 5,8-epoxy xanthophylls diasteroisomers (neochrome, auroxanthin, luteoxanthin, flavoxanthin, chrysanthemaxanthin). Copyright © 2010 John Wiley & Sons, Ltd. [source] Simultaneous quantification of cyclophosphamide, 4-hydroxycyclophosphamide, N,N,,N, -triethylenethiophosphoramide (thiotepa) and N,N,,N, -triethylenephosphoramide (tepa) in human plasma by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2004Milly E. de Jonge Abstract The alkylating agents cyclophosphamide (CP) and N, N,, N, -triethylenethiophosphoramide (thiotepa) are often co-administered in high-dose chemotherapy regimens. Since these regimens can be complicated by the occurrence of severe and sometimes life-threatening toxicities, pharmacokinetically guided administration of these compounds, to reduce variability in exposure, may lead to improved tolerability. For rapid dose adaptations during a chemotherapy course, we have developed and validated an assay, using liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS), for the routine quantification of CP, thiotepa and their respective active metabolites 4-hydroxycyclophosphamide (4OHCP) and N, N,, N, -triethylenephosphoramide (tepa) in plasma. Because of the instability of 4OHCP in plasma, the compound is derivatized with semicarbazide (SCZ) immediately after sample collection and quantified as 4OHCP-SCZ. Sample pretreatment consisted of protein precipitation with a mixture of methanol and acetronitrile using 100 µl of plasma. Chromatographic separation was performed on an Zorbax Extend C18 column (150 × 2.1 mm i.d., particle size 5 µm), with a quick gradient using 1 mM ammonia solution and acetonitrile, at a flow-rate of 0.4 ml min,1. The analytical run time was 10 min. The triple quadrupole mass spectrometer was operating in the positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over the concentration ranges 200,40 000 ng ml,1 for CP, 50,5000 ng ml,1 for 4OHCP-SCZ and 5,2500 ng ml,1 for thiotepa and tepa, using 100 µl of human plasma. These dynamic concentration ranges proved to be relevant in daily practice. Hexamethylphosphoramide was used as an internal standard. The coefficients of variation were <12% for both intra-day and inter-day precisions for each compound. Mean accuracies were also between the designated limits (±15%). This robust and rapid LC/MS/MS assay is now successfully applied for routine therapeutic drug monitoring of CP, thiotepa and their metabolites in our hospital. Copyright © 2004 John Wiley & Sons, Ltd. [source] Effect of buffer cations and of H3O+ on the charge states of native proteins.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2003Significance to determinations of stability constants of protein complexes Abstract The progressive reduction of charge in charge states of non-denatured proteins (lysozyme, ubiquitin, and cytochrome c), observed with nanospray in the positive ion mode, when the buffer salt ammonium acetate is replaced by ethylammonium acetates (EtNH3Ac, Et2NH2Ac and Et3NHAc) is rationalized on the basis of the charge residue model (CRM). The charge states of the multiply protonated protein are shown to be controlled by the increasing gas-phase basicities, GB(B), of the bases(B) NH3, EtNH2, Et2NH and Et3N. Charge states derived from evaluated apparent gas-phase basicities GBapp of the basic side-chains of the protein and the known GB(B) of the above bases are found to be in agreement with the experimentally observed charge states. This is a requirement of the CRM, because in this model the small positive ions (the buffer cations in the present case) at the surface of the electrospray droplets are the excess ions that provide the charge of the final small droplet that contains the protein molecule and on evaporation of the solvent transfer the charge to the protein. The observed charge states in the absence of buffer salts, i.e. pure water, are attributed to excess H3O+ ions produced by the electrolysis process that attends electrospray. A proposed extended mechanism provides predictions of factors that determine the sensitivity for detection of the multiply protonated proteins. Consideration of restraints imposed by the CRM lead to some simple predictions for conditions that should be present to obtain accurate determinations by electrospray and nanospray of stability constants for the protein,complex equilibrium in aqueous solution. Copyright © 2003 John Wiley & Sons, Ltd. [source] Effect of instrument tuning on the detectabilityof biopolymers in electrospray ionization mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2003Herbert Oberacher Abstract Electrospray ionization mass spectrometry of multiply charged biopolymer ions of different molecular size revealed a strong influence of tuning parameters on their detectability in quadrupole ion trap and triple quadrupole mass spectrometers. Hence, after optimizing the ion optical parameters with the signal of the 4, charge state of (dT)24 (low charge state tuning), a tenfold increase in the signal-to-noise ratio for a mixture of oligodeoxythymidylic acids (n = 12,18) was obtained compared with the results achieved with tune parameters optimized with a synthetic 80-mer oligodeoxynucleotide. By contrast, a detection limit in the upper femtomole region could only be reached for a 104-mer oligodeoxynucleotide utilizing the 24, charge state of the 80-mer (high charge state tuning). The same effect was observed for proteins investigated in the positive ion mode using low and high charge states of cytochrome c and carbonic anhydrase, respectively, for instrument tuning. By comparing the settings for low and high charge state tuning, it became obvious that the most significant difference was observed in the potential applied to the heated metal capillary used to transfer ions from the atmospheric pressure to the vacuum region of the ion source. Taking advantage of the optimized tuning procedure, the molecular mass of a 61 base pair product of polymerase chain reaction was accurately determined by electrospray ionization mass spectrometry on-line interfaced to ion-pair reversed-phase high-performance liquid chromatography. Copyright © 2003 John Wiley & Sons, Ltd. [source] Simultaneous determination of avermectins in bovine tissues by LC-MS/MSJOURNAL OF SEPARATION SCIENCE, JSS, Issue 21 2009Koichi Inoue Abstract Analytical method for the simultaneous quantification of avermectins (AVMs), abamectin B1a, abamectin 8,9-Z isomer B1a, emamectine benzoate B1a, emamectine benzoate 8,9-Z isomer B1a, ivermectin, eprinomectin B1a, doramectin and moxidectin in bovine tissues (muscle, liver and fat) was developed by LC-MS/MS in electrospray positive ion mode. The separation was achieved on a short TSK-GEL ODS 100V column with the mobile phase consisting of acetonitrile and aquatic 0.1,mM ammonium formate containing 0.1% formic acid v/v at a flow rate of 0.2,mL/min with gradient elution. Liquid,liquid extraction with isooctane was used for the sample extraction/preparation of analytes in bovine samples. The linearity of the calibration curves was excellent in matrix-matched standards, and yielded the coefficients (r2=0.997,0.999, range from LOQ to 500, 1000 or 5000,ng/g) of determination of the target analytes. Recoveries were in the range of 87.9,99.8% with associated precision values (within-day: 1.5,7.4%, n=6, and between-day: 1.5,8.4% for 3 days) for repeatability and reproducibility. LC-MS/MS method has been proven to be highly efficient and suitable for the simultaneous determinations of eight AVMs in bovine tissue samples. [source] HPLC-MS of anthraquinoids, flavonoids, and their degradation products in analysis of natural dyes in archeological objectsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2007Izabella Surowiec Abstract LC with MS detection was optimized for sensitive and selective analysis of main classes of natural dyes used in ancient times for dyeing textiles , red anthraquinoids, yellow flavonoids, and known degradation products of flavonols , hydroxybenzoic acids. Fragmentation patterns of both negative and positive molecular ions for the above mentioned compounds were investigated. Three acquisition modes of MS analysis: scanning, SIM, and multiple reaction monitoring (MRM) in both positive and negative ion modes were optimized and compared with each other and with the UV-Vis diode-array detection. Even though in the applied chromatographic system formic acid was used in the mobile phase, SIM in the negative ion mode was the most selective and sensitive detection for all the investigated compounds when both mixtures of standards and analysis of extracts from archeological samples were concerned, with one exception , alizarin, for which MS detection in positive ion mode was more sensitive. Detection limits obtained with MS detection for all investigated compounds except quinizarin were lower than the ones obtained with the diode-array UV-Vis detection, making MS detection the most suitable tool for the analysis of natural dyes and their degradation products in extracts from archeological samples. [source] Rapid quantification of sucrose esters in oriental tobacco by liquid chromatography-ion trap mass spectrometryJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2007Li Ding Abstract A rapid and sensitive LC-MS/MS method was developed for the quantitative determination of sucrose esters (SEs) in Oriental tobacco samples. The sample preparation involved a 10-min sonication extraction procedure with acetone and five-fold dilution of the extract with methanol. The experiment was carried out in positive ion mode by ESI IT mass spectrometer. Because of lack of authentic standards of SEs, sucrose octa-acetate (internal standard, IS) was used as a surrogate to validate the proposed method. Matrix-matched standard calibration was used for quantification of IS in the spiked samples. Under optimized MS/MS conditions, an LOQ of 3.9 ,g/g was achieved for IS, with an LOD of about 1.2 ,g/g. Recoveries for IS were 95,97%. Among 19 monitored SEs, the contents of 11 SEs had RSDs lower than 13.7%. The method, with very little sample handling and good sensitivity, was applied to the rapid quantification of SEs in four Oriental tobacco samples. It appears that the sum of contents of the five SEs with MW 650, 664, and 678 Da occupied approximately 80% of the total content of SEs. [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] Characterization of a peptide family from the skin secretion of the Middle East Tree Frog Hyla savignyi by composition-based de novo sequencingRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2010Markus Langsdorf A new tryptophyllin-like peptide family was found in the skin secretion of the tree frog Hyla savignyi. Peptides were characterized by database-independent sequencing strategies and specific ion fragmentation features were investigated. Skin secretions from specimens of Hyla savignyi were collected by mild electrical stimulation. Peptides were separated by reversed-phase nano-high-performance liquid chromatography (nanoHPLC) and mass spectra were acquired online by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Peptides were characterized by manual de novo sequencing and by composition-based sequencing (CBS), appearing mostly as C-terminal free acids and as their acid amide analogs. Amide peptides yielded lower intensities of y-type ions after collision-induced dissociation (CID) than their acid analogs. A mechanism of internal b-ion formation (positive ion mode) and of CO2 elimination (negative ion mode) is proposed. We also exemplified phenomena such as the proline effect and formation of non-direct sequence ions after sequence rearrangements. The occurrence of rearrangement products, of internal ions and of the proline effect made the CID spectra highly complex. CBS analysis nevertheless resulted in successful and highly reliable sequence analysis. Copyright © 2010 John Wiley & Sons, Ltd. [source] Study of fragmentation pathways of lithiated ,,, -unsaturated thioesters by electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2010Cheng Guo The fragmentation pathways of lithiated ,,, -unsaturated thioesters with different substituents were investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS) in positive ion mode. In mass spectrometry of the ,,, -unsaturated thioesters, Ar-CHCH-CO-S-Ph, loss of PhSLi and elimination of a thiophenol were the two major fragmentation reactions of the lithiated molecules. The elemental compositions of all the ions were confirmed by high-resolution Fourier transform ion cyclotron resonance tandem mass spectrometry (FTICR-MS/MS). The thioesters studied here were para -monosubstituted on the phenyl ring of cinnamoyl and the electron-withdrawing groups favored loss of a thiophenol, whereas the electron-releasing groups strongly favored the competing reaction leading to the loss of PhSLi to form a cinnamoyl cation, Ar-CHCHCO+. The intensity ratios of the two competitive product ions were well correlated with the , substituent constants. The mechanisms of these two competing routes were further investigated by density functional theory (DFT) calculations. Copyright © 2010 John Wiley & Sons, Ltd. [source] Drug impurity profiling by capillary electrophoresis/mass spectrometry using various ionization techniquesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2009Paul Hommerson Capillary electrophoresis/mass spectrometry (CE/MS) is predominantly carried out using electrospray ionization (ESI). Recently, atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) have become available for CE/MS. With the VUV lamp turned off, the APPI source may also be used for CE/MS by thermospray ionization (TSI). In the present study the suitability of ESI, APCI, APPI and TSI for drug impurity profiling by CE/MS in the positive ion mode is evaluated. The drugs carbachol, lidocaine and proguanil and their potential impurities were used as test compounds, representing different molecular polarities. A background electrolyte of 100,mM acetic acid (pH 4.5) provided baseline separation of nearly all impurities from the respective drugs. APPI yielded both even- and odd-electron ions, whereas the other ionization techniques produced even-electron ions only. In-source fragmentation was more pronounced with APCI and APPI than with ESI and TSI, which was most obvious for proguanil and its impurities. In general, ESI and TSI appeared the most efficient ionization techniques for impurities that are charged in solution achieving detection limits of 100,ng/mL (full-scan mode). APPI and APCI showed a lower efficiency, but allowed ionization of low and high polarity analytes, although quaternary ammonium compounds (e.g. carbachol) could not be detected. Largely neutral compounds, such as the lidocaine impurity 2,6-dimethylaniline, could not be detected by TSI, and yielded similar detection limits (500,ng/mL) for ESI, APPI and APCI. In many cases, impurity detection at the 0.1% (w/w) level was possible when 1,mg/mL of parent drug was injected with at least one of the CE/MS systems. Overall, the tested CE/MS systems provide complementary information as illustrated by the detection and identification of an unknown impurity in carbachol. Copyright © 2009 John Wiley & Sons, Ltd. [source] Electrospray ionization tandem mass spectrometry fragmentation of protonated flavone and flavonol aglycones: a re-examinationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2009Gonçalo C. Justino Flavonoids are important phytochemicals which have been intensively studied in the last decades in view of their antioxidant activity, which is of particular importance in the case of flavones and flavonols, that differ in a single 3-OH group. Mass spectrometry has been used to elucidate the structures of many types of flavonoids and their metabolites. The work we present here is focused on the electrospray ionization tandem mass spectrometry (ESI-MS/MS) analysis of flavone and flavonols aglycones. Their fragmentation mechanisms in the positive ion mode are described and compared with previously reported mechanisms. We analyzed flavonoid derivatives produced by reaction of the flavonoids with chemically synthesized hypohalous acids (HOCl, HOBr and HOI) and peroxynitrite, reactive species involved in the inflammatory response. All the proposed pathways have been analyzed using computational chemistry methods in order to seek for possible variations and establish the most plausible ones. We observed that the losses of one and two CO molecules can be useful in terms of antioxidant activity prediction. Losses of one and two C2H2O groups are also informative in terms of structure and activity predictions. The retro-Diels-Alder fragmentations, and subsequent neutral losses, were reviewed and, according to our calculations, the most plausible structures for the product ions were established. These fingerprints will be of great value for differentiating flavonoids from other compounds in complex biological mixtures and for a thorough structural identification of flavonoid aglycones and their invivo metabolites. Copyright © 2008 John Wiley & Sons, Ltd. [source] Degradation of the insecticides thiamethoxam and imidacloprid by zero-valent metals exposed to ultrasonic irradiation in water medium: electrospray ionization mass spectrometry monitoringRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2008Renata P. Lopes The degradation of thiamethoxam (1) and imidacloprid (2), prototype neonicotinoid insecticides bearing a characteristic N-NO2 moiety in their structures, promoted by a number of zero-valent metals (Fe, Sn, Zn) upon ultrasonic irradiation in acidic aqueous solution (pH 2) was investigated. It was verified that thiamethoxam (1) and imidacloprid (2) are quickly and almost completely consumed under these experimental conditions (degradation >90% after a reaction time of 30,min) and that ultrasonic irradiation strongly enhances the degradation rate for both insecticides, especially when zinc and tin are employed. Based on the results from electrospray ionization mass (and tandem mass) spectrometry in the positive ion mode, degradation routes for both insecticides, comprising an initial NO2,,,NH2 reduction, were proposed. In addition, products from the dehydrochlorination of imidacloprid were also found to be formed under these conditions. Copyright © 2008 John Wiley & Sons, Ltd. [source] Structural characterization and identification of ecdysteroids from Sida rhombifolia L. in positive electrospray ionization by tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2008Yan-Hong Wang Seven ecdysteroids isolated from Sida rhombifolia L. were studied by electrospray ionization multi-stage tandem mass spectrometry (ESI-MSn) in the positive ion mode using an ion trap analyzer and high-performance liquid chromatography coupled with a diode-array detector (HPLC/DAD). The HPLC experiments were performed by means of a reversed-phase C18 column and a binary mobile phase system consisting of water (containing 0.05% formic acid) and acetonitrile (containing 0.05% formic acid) under gradient elution conditions. According to mass spectral features and the substitution at C-2, C-20, C-24 and C-25, ecdysteroids in S. rhombifolia were classified into three sub-groups. Structural identification of these three sub-groups of ecdysteroids was established by LC/multi-stage ion trap mass spectrometry on-line or off-line. The fragmentation patterns of ecdysteroids yielded ions of successive loss of 1,4 water molecules. Furthermore, ions corresponding to the complete loss of the side chain at C-17 will help to identify the sub-groups of ecdysteroids in addition to containing a hydroxyl moiety at one of the above-mentioned positions. Based on the HPLC retention behavior, the diagnostic UV spectra and the molecular structural information provided by ESI-MSn spectra, a total of nine naturally occurring ecdysteroids were identified, of these two are identified for the first time in S. rhombifolia. Copyright © 2008 John Wiley & Sons, Ltd. [source] Gas-phase fragmentation study of novel synthetic 1,5-benzodiazepine derivatives using electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2008Mohamed Rida The fragmentation patterns of a series of three novel synthesized 3-hydroxy-4-phenyl-tetrahydro-1,5-benzodiazepin-2-ones (1,3), possessing the same backbone structure, were investigated using electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS) techniques. A simple methodology, based on the use of ESI (positive ion mode) and by increasing the declustering potential in the atmospheric pressure/vacuum interface, collision-induced dissociation (CID), was used to enhance the formation of the fragment ions. In general, the novel synthetic 1,5-benzodiazepine derivatives afforded, in the gas phase, both protonated and sodiated molecules. This led to the confirmation of the molecular masses and chemical structures of the studied compounds. Exact accurate masses were measured using a high-resolution ESI-quadrupole orthogonal time-of-flight (QqToF)-MS/MS hybrid mass spectrometer instrument. The breakdown routes of the protonated molecules were rationalized by conducting low-energy collision CID-MS/MS analyses (product ion- and precursor ion scans) using a conventional quadrupole-hexapole-quadrupole (QhQ) tandem mass spectrometer. All the observed major fragmentations for the 1,5-benzodiazepines occurred in the saturated seven-membered ring containing the nitrogen atoms. These formed a multitude of product ions by different breakdown routes. All the major fragmentations involved cleavages of the N -1,C -2 andC -3,C -4 bonds. These occurred with concomitant eliminations of glyoxal, benzene and ethyl formate, forming the product ion at m/z 119, which was observed in all the studied compounds. In addition, an unique simultaneous CID-MS/MS fragmentation was noticed for the 1,5-benzodiazepines 1 and 3, which occurred by a pathway dictated by the substituent located on the N -1-position. It was evident that the aromatic ring portion of the 1,5-benzodiazepines was resistant to CID-MS/MS fragmentation. Re-confirmation of the various geneses of the product ions was achieved by conducting a series of precursor ion scans. ESI-MS and CID-MS/MS analyses have thus proven to be a specific and very sensitive method for the structural identification of these novel 1,5-benzodiazepine derivatives. Copyright © 2008 John Wiley & Sons, Ltd. [source] Plasma free fatty acid profiling in a fish oil human intervention study using ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2008Nicole Zehethofer A rapid method was developed for the simultaneous profiling of 29 free fatty acids in plasma using ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometry (UPLC/ESI-MS/MS). Barium acetate was used as the cationization agent in the positive ion mode for sensitive multiple reaction monitoring (MRM) experiments. The cis- and trans -C18:1 and -C18:2 isomers were baseline-separated using two tandem reversed-phase C18 UPLC columns, while identification of two pairs of positional isomers of C18:3 and C20:3 required isomer-specific product ions, as the analytes were not chromatographically resolved. The assay linearity was greater than three orders of magnitude and correlation coefficients were >0.99; the limits of detections were typically less than 0.2,µM. The method was successfully applied to plasma free fatty acid profiling of samples from volunteers who participated in a randomized crossover study involving the administration of either placebo or fish oil capsules. The results clearly indicate the ability to measure the time profiles of the n -3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in plasma for the volunteers given fish oil capsules while the concentrations of the other free fatty acids and the total free fatty acid concentration in plasma remained virtually constant. Copyright © 2008 John Wiley & Sons, Ltd. [source] Analysis of triacetone triperoxide (TATP) and TATP synthetic intermediates by electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2008Michael E. Sigman The explosive triacetone triperoxide (TATP) has been analyzed by electrospray ionization mass spectrometry (ESI-MS) on a linear quadrupole instrument, giving a 62.5,ng limit of detection in full scan positive ion mode. In the ESI interface with no applied fragmentor voltage the m/z 245 [TATP,+,Na]+ ion was observed along with m/z 215 [TATP,+,Na , C2H6]+ and 81 [(CH3)2CO,+,Na]+. When TATP was ionized by ESI with an applied fragmentor voltage of 75,V, ions at m/z 141 [C4H6O4,+,Na]+ and 172 [C5H9O5,+,Na]+ were also observed. When the precipitates formed in the synthesis of TATP were analyzed before the reaction was complete, a new series of ions was observed in which the ions were separated by 74,m/z units, with ions occurring at m/z 205, 279, 353, 427, 501, 575, 649 and 723. The series of evenly spaced ions is accounted for as oligomeric acetone carbonyl oxides terminated as hydroperoxides, [HOOC(CH3)2{OOC(CH3)2}nOOH,+,Na]+ (n,=,1, 2,,,8). The ESI-MS spectra for this homologous series of oligoperoxides have previously been observed from the ozonolysis of tetramethylethylene at low temperatures. Precipitates from the incomplete reaction mixture, under an applied fragmentor voltage of 100,V in ESI, produced an additional ion observed at m/z 99 [C2H4O3,+,Na]+, and a set of ions separated by 74,m/z units occurring at m/z 173, 247, 321, 395, 469 and 543, proposed to correspond to [CH3CO{OOC(CH3)2}nOOH,+,Na]+ (n,=,1,2,,,5). Support for the assigned structures was obtained through the analysis of both protiated and perdeuterated TATP samples. Copyright © 2007 John Wiley & Sons, Ltd. [source] Characterization of isoquinoline alkaloids, diterpenoids and steroids in the Chinese herb Jin-Guo-Lan (Tinospora sagittata and Tinospora capillipes) by high-performance liquid chromatography/electrospray ionization with multistage mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2006Yufeng Zhang This study sought to determine the primary components (isoquinoline alkaloids, diterpenoids and steroids) in crude extracts of the Chinese herb Jin-Guo-Lan, prepared from the roots of Tinospora sagittata and T. capillipes, by liquid chromatography/electrospray ionization multistage mass spectrometry coupled with diode-array detection (LC-DAD/ESI-MSn). After separation on a reversed-phase C18 column using gradient elution, positive and negative ESI-MS experiments were performed. In positive ion mode, the three types of compounds showed very different characteristic ions: strong [M]+ or [M+H]+ ions were observed for isoquinoline alkaloids; [M+NH4]+ and/or [M+HCO2]+ for diterpenoids; [M+HnH2O]+ (n=1,3) for steroids. These adduct ions and/or fragments were used to deduce the mass and categories of known and unknown components in crude extracts, and their structures were further confirmed by ESI-MSn in positive ion mode. Moreover, UV absorption peaks obtained from DAD provided useful functional group information to aid the MSn -based identification. As a result, 11 compounds were unambiguously identified by comparing with standard compounds and 13 compounds were tentatively identified or deduced according to their MSn data. Two of these compounds (13-hydroxycolumbamine and 13-hydroxyjatrorrhizine) were found to be new compounds and another one (13-hydroxypalmatine) was detected for the first time as a natural product. In addition, a [M·CH3H2O].+ ion in MS2 of [M]+ after in-source collision-induced dissociation was used to differentiate positional isomers of protoberberine alkaloids, columbamine and jatrorrhizine. Although the roots of T. sagittata and T. capillipes contain almost identical compounds, the content of the compounds in them is dramatically different, suggesting the necessity for further comparison of the bioactivities of the two species. Copyright © 2006 John Wiley & Sons, Ltd. [source] Simultaneous quantification of CTN986 and its deglycosylation products in rat serum using liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2006Jifen Guo A quantitative method for the simultaneous determination of CTN986, a flavonol triglycoside, and its two deglycosylation products rutin and hirsutin in rat serum was developed and validated for the investigation of the pharmacokinetics of CTN986. Analytes were isolated from the serum samples (200,µL) prior to analysis by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using C18 solid-phase extraction, and were separated on a Zorbax C8 reversed-phase column with an isocratic mobile phase consisting of methanol/isopropanol/water/formic acid (20:10:70:0.1, v/v/v/v). The protonated analytes generated in the positive ion mode were monitored through multiple reaction monitoring in an eletrospray ionization source. Calibration was performed by internal standardization with CTN987, a flavonoid structurally similar to CTN986, and regression curves were constructed ranging from 2 to 1000,ng/mL in 200,µL serum samples. The intra- and inter-day precision values were below 11% and accuracy was between ,2.37 and 1.4% for all quality control samples. This quantitation method was successfully applied to pharmacokinetic studies of CTN986 in rats following oral and intravenous administration. Rutin and hirsutin were not detected in rat serum. Copyright © 2006 John Wiley & Sons, Ltd. [source] Nitrogen purity influences the occurrence of As+ ions in high-performance liquid chromatography/electrospray ionization mass spectrometric analysis of four common arsenosugarsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2003Doris Kuehnelt High-performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC/ESI-MS) can provide both elemental and molecular information and, therefore, is a very useful tool for the identification of arsenic compounds. When a method for the identification of four arsenosugars was employed in our laboratory with an HPLC/ESI-MS system equipped with a Whatman model 75-72 nitrogen generator, a signal at m/z 75 (As+) could not be observed. When the HPLC/ESI-MS system was operated with nitrogen 5.0 (nitrogen of a purity of at least 99.999%) all four arsenosugars gave a signal at m/z 75. Because of this observation the influence of the quality of the nitrogen drying gas on the fragmentation of the four arsenosugars was systematically investigated. Standard solutions containing the four arsenosugars (0.5 ng As each) were separated on an anion-exchange column and detected with ESI-MS in the positive ion mode by monitoring the signals for [M+H]+, m/z 237, 91, and 75. Nitrogen with defined oxygen concentrations was used as drying gas. The purity of the nitrogen ranged from 99 to 99.999% (10,400 to 10 ppm oxygen impurity). The nitrogen with 99% purity gave no signal at m/z 75, but signals were obtained at m/z 91, 237, and for [M+H]+. When higher purity nitrogen (99.9%) was used, a signal was obtained at m/z 75, which accounted for 0.8,1.1% (depending on the kind of arsenosugar) of the sum of the signals for m/z 75, 91, 237 and [M+H]+. As the level of oxygen in the nitrogen decreased, the m/z 75 signal increased to 2.0,3.1%. This was accompanied by a concomitant decrease in the m/z 91 signal from 5.2,6.6% to 0.7,1.5%, whereas the signals for [M+H]+ and m/z 237 were essentially unchanged. Signals at m/z 75 with intensities comparable with those observed for the 99.9% pure nitrogen were also obtained for all the arsenosugars when the HPLC/ESI-MS system was operated with a Domnick Hunter Nitrox UHPLCMS18 nitrogen generator. Dimethylarsinic acid, arsenobetaine, trimethylarsine oxide, arsenocholine and the tetramethylarsonium cation also gave no signal at m/z 75 when they were analyzed with the Whatman model 75-72 nitrogen generator, but clear signals at m/z 75 were observed with the Domnick Hunter Nitrox UHPLCMS18 nitrogen generator. A nitrogen quality of at least 99.9% is required to obtain elemental information (m/z 75) when arsenic compounds are investigated by HPLC/ESI-MS. Molecular and elemental information from one chromatographic run is a valuable tool for the characterization of unknown arsenic compounds. Copyright © 2003 John Wiley & Sons, Ltd. [source] Investigation of reduction of Cu(II) complexes in positive-ion mode electrospray mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2001Luca Gianelli The electrospray ionization mass spectrometry (ESI-MS) behavior of seven Cu(II) complexes with tetradentate ligands has been studied. An unexpected reduction process, in positive ion mode, of the Cu oxidation state was observed, and shown to be due to charge transfer between the metal complex and the solvent molecules in the gas phase. Ion trap collision-induced dissociation experiments and deuterated solvents were used to support the proposed mechanism that is not a common electrochemical redox reaction at the ESI tip, but a gas-phase process. A series of solvents (acetonitrile, methanol, ethanol, propanol and iso -butanol) were tested, and a correlation between ionization energy (IE) and the amount of Cu(I) produced in ESI has been demonstrated for the alcohols, although some other solvent properties should also be taken into account. The electrochemical reduction potential of the complexes in solution is also an important parameter, since complexes more easily reduced in solution are also easier to reduce in the gas phase. Copyright © 2001 John Wiley & Sons, Ltd. [source] Phosphopeptide analysis by positive and negative ion matrix-assisted laser desorption/ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2001Katharina Janek This article describes a simple procedure for the detection of phosphorylated peptides by comparable positive and negative ion mode matrix-assisted laser desorption/ionization mass spectrometry measurements. Based on studies with phosphorylated peptides (EAIXAAPFAK, X,=,pS, pT, pY) and their corresponding non-phosphorylated analogs, it was found that phosphopeptides, which are characterized by a low ionization efficiency in the positive ion mode, exhibit drastically increased signal intensities in the negative ion mode compared to their non-phosphorylated analogs. The effect was successfully used to identify phosphorylated sequences of the commonly used phosphoprotein standards, protein kinase A and ,-casein, by peptide mass fingerprint analyses of the corresponding Lys C and trypsin digests using both (positive and negative) ion modes. The comparison of positive and negative ion spectra of a given protein digest (relative intensity[M,,,H],/relative intensity[M,+,H]+) can be used to identify any phosphopeptides present which may then be separated and analyzed further. Copyright © 2001 John Wiley & Sons, Ltd. [source] Liquid chromatographic,tandem mass spectrometry assay for quantitation of a novel antidiabetic S002-853 in rat plasma and its application to pharmacokinetic study,BIOMEDICAL CHROMATOGRAPHY, Issue 7 2010N. Gautam Abstract A sensitive and selective LC-MS/MS method has been developed and validated for the estimation of novel antidiabetic synthetic flavonoid S002-853 in rat plasma using centchroman as an internal standard. The method involves a simple two-step liquid,liquid extraction with diethyl ether. The analyte was chromatographed on a Pierce Spheri-5, guard cyano column (30 × 4.6,,mm i.d., 5,,µm) with isocratic mobile phase consisting of methanol,ammonium acetate buffer (pH 4.6, 10,,mm; 90,:,10, v/v) at a flow rate of 0.75,,mL/min. The API 4000 triple-quadrupole LC,MS/MS system was operated under multiple reaction-monitoring mode. The ionization was performed by electrospray ionization technique in positive ion mode. The chromatographic run time was 6,,min and the weighted (1/x2) calibration curves were linear over the range 0.78,400,,ng/mL. The limit of detection and lower limit of quantification were 0.195 and 0.78,,ng/mL, respectively. The intra- and inter-batch accuracy (%bias) and precision (%RSD) were found to be less than 8.47 and 11.6% respectively. The average absolute recoveries of S002-853 and internal standard from spiked plasma samples were >90%. S002-853 was stable for 8,,h at ambient temperature, 4 weeks at ,60°C and after three freeze,thaw cycles. The assay was successfully applied to determine the pharmacokinetic parameters in male Sprague,Dawley rats after an oral dose administration at 25,,mg/kg. Copyright © 2009 John Wiley & Sons, Ltd. [source] Measurement of fexofenadine concentration in micro-sample human plasma by a rapid and sensitive LC-MS/MS employing protein precipitation: application to a clinical pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 3 2010Daqing Guo Abstract A simple, rapid and sensitive liquid chromatography/positive ion electro-spray tandem mass spectrometry method (LC-MS/MS) was developed and validated for the quantification of fexofenadine with 100,,L human plasma employing glipizide as internal standard (IS). Protein precipitation was used in the sample preparation procedure. Chromatographic separation was achieved on a reversed-phase C18 column (5,,m, 100 × 2.1,mm) with methanol,:,buffer (containing 10,mmol/L ammonium acetate and 0.1% formic acid; 70,:,30, v/v) as mobile phase. The total chromatographic runtime was approximately 3.0,min with retention time for fexofenadine and IS at approximately 1.9 and 2.1,min, respectively. Detection of fexofenadine and IS was achieved by LC-MS/MS in positive ion mode using 502.1 , 466.2 and 446.0 , 321.1 transitions, respectively. The method was proved to be accurate and precise at linearity range of 1,600,ng/mL with a correlation coefficient (r) of ,0.9976. The validated method was applied to a pharmacokinetic study in human volunteers following oral administration of 60 or 120,mg fexofenadine formulations, successfully. Copyright © 2009 John Wiley & Sons, Ltd. [source] Development and validation of UPLC-MS/MS method for simultaneous determination of gestodene and ethinyl estradiol in rat plasmaBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Zhili Xiong Abstract A selective and sensitive ultra-performance liquid chromatography method with tandem mass spectrometric detection for simultaneous determination of gestodene (GES) and ethinyl estradiol (EE) in rat plasma was developed and validated. GES, EE and the internal standard, norgestrel, were extracted with ethyl acetate, derivatized (EE only) with dansyl chloride and then back-extracted into diethyl ether-hexane (2:1, v/v). The separation was performed on an ACQUITY UPLCÔ BEH C18 column with gradient elution using mobile phase consisting of acetonitrile and water (both containing 0.1% formic acid). The detection was carried out by means of electrospray ionization (ESI) mass spectrometry in positive ion mode with multiple-reaction monitoring. Calibration curves of GES and EE were linear (r2,,,0.99) over the concentration ranges 1.59,159 and 0.196,78.4,ng/mL, respectively. The intra- and inter-day precisions were not more than 6.9 and 12.9% for GES and 10.6 and 9.0% for EE, and the accuracies were ,2.5,8.0% for GES, and ,7.2,0.19% for EE, respectively. The method herein described was superior to previous methods and was applicable to the pharmacokinetic study of GES and EE in rats. Copyright © 2009 John Wiley & Sons, Ltd. [source] A rapid and specific approach for direct measurement of donepezil concentration in human plasma by LC-MS/MS employing solid-phase extractionBIOMEDICAL CHROMATOGRAPHY, Issue 2 2009Hiten J. Shah Abstract A selective, rapid and simple liquid chromatography,tandem mass spectrometry (LC-MS/MS) method is described for assay of donepezil in human plasma using escitalopram as an internal standard. Chromatographic separation was achieved on a Betabasic-C8, 5 µm, 100 × 4.6 mm column using methanol:water:formic acid (90:9.97:0.03, v/v/v) as mobile phase. Detection of donepezil and internal standard was achieved by ESI MS/MS in positive ion mode using 380.20/91.10 and 325.13/262.00 transitions, respectively. The linearity over the concentration range of 0.15,50 ng/mL for donepezil was obtained and the lower limit of quantification was 0.15 ng/mL. For each level of quality control samples, inter-day and intra-day precisions (RSD) were ,8.92 and 10.35% and accuracy (%RE) were ,7.33% and 9.33%, respectively. The recovery was more than 88.50% for both donepezil and internal standard by solid-phase extraction, eliminating evaporation and reconstitution steps. Copyright © 2008 John Wiley & Sons, Ltd. [source] Simultaneous determination of estramustine phosphate and its four metabolites in human plasma by liquid chromatography,ionspray mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 5 2004M. Breda Abstract A sensitive and selective method, using liquid chromatography,ionspray mass spectrometry, was developed and validated for the simultaneous determination of Estracyt (estramustine phosphate) and its four metabolites, estramustine, estromustine, estrone and estradiol, in human plasma. Deuterated internal standards were available for all analytes. The ,ve compounds were extracted from plasma by protein precipitation with acetonitrile. The chromatographic separation was performed using a Zorbax SB C18, (150 × 4.6 mm i.d., 5 µm) reversed-phase column under gradient conditions with a mobile phase containing 2 mm ammonium acetate buffer (pH 6.8) and acetonitrile. MS detection was by electrospray ionization with multiple reaction monitoring in the positive ion mode for estramustine phosphate, estromustine and estramustine, and in the negative ion mode for estrone and estradiol. The limit of quantitation was 10 ng/mL for estramustine phosphate, 3 ng/mL for estromustine, estramustine and estrone and 30 ng/mL for estradiol. Linearity was veri,ed from these LLOQs up to about 4000 ng/mL for the parent drug and 2000 ng/mL for the metabolites. Inter-day precision and accuracy values were all less than 15%. This assay was applied successfully to the routine analysis of human plasma samples collected in cancer patients administered estramustine phosphate intravenously. Copyright © 2003 John Wiley & Sons, Ltd. [source] Mass spectral characterization of phloroglucinol derivatives hyperforin and adhyperforinRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2006Lekha Sleno Active phloroglucinol constituents of Hypericum perforatum (St. John's wort) extracts, hyperforin and adhyperforin, have been studied following ion activation using tandem mass spectrometry (MS/MS) and complemented by accurate mass measurements. These two compounds were readily analyzed as protonated and deprotonated molecules with electrospray ionization. MS/MS and MS3 data from a quadrupole-linear ion trap tandem mass spectrometer were employed to elucidate fragmentation pathways. Fourier transform ion cyclotron resonance measurements afforded excellent mass accuracies for the confirmation of elemental formulae of product ions formed via infrared multiphoton dissociation and sustained off-resonance irradiation collision-induced dissociation. Fragmentation schemes have been devised for the dissociation of hyperforin and adhyperforin in negative and positive ion modes. This information is expected to be especially valuable for the characterization of related compounds, such as degradation products, metabolites and novel synthetic analogs of hyperforin. Copyright © 2006 John Wiley & Sons, Ltd. [source] Sample preparation effects in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry of partially depolymerised carboxymethyl celluloseRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2003Dane Momcilovic Sample preparation effects in matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) of partially depolymerised carboxymethyl cellulose (CMC) have been investigated. The depolymerisation was either enzymatic or acidic. Fractions of enzymatically depolymerised CMC were collected from size-exclusion chromatography (SEC) and further investigated by MALDI-TOFMS. 2,5-Dihydroxybenzoic acid was used as matrix, dissolved in H2O due to the poor solubility of CMC in suitable organic solvents. The samples were dried by two methods, in ambient atmosphere and at reduced pressure. Under reduced pressure the sample spot homogeneity increased. This drying method, however, produced additional adduct peaks in the mass spectra originating from ion exchange on the CMC oligomers. Analysis of CMC could be performed in both negative and positive ion modes. Mass discrimination and variation in ionisation efficiency were demonstrated by comparing mass spectra with SEC data. Measurements of the degree of substitution (DS) were performed on three CMCs with different DS values, which were depolymerised in trifluoroacetic acid. The three CMCs were easily distinguished from one another, but the obtained DS values deviated from the values supplied by the manufacturer. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||