bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas chromatography/mass spectrometric characterisation of pyrolysis/silylation products of glucose and cellulose
Authors: Fabbri Daniele , Chiavari Giuseppe , Prati Silvia , Vassura Ivano , Vangelista Marta 
Published: December 2002

AbstractThe mass spectra of trimethylsilyl (TMS) derivatives of possible hydroxylated pyrolysis products of glucose and cellulose were recorded by gas chromatography/mass spectrometry (GC/MS) analyses of TMS derivatives of 2‐hydroxymethylfuran, 2‐hydroxy‐1‐methyl‐1‐cyclopenten‐3‐one, 5‐(hydroxymethyl)‐2‐furaldehyde, 5‐methyl‐2‐furoic acid, 4‐hydroxy‐6‐methyl‐(2H)‐pyran‐2‐one, 2‐methyl‐3‐hydroxy‐(4H)‐pyran‐4‐one (maltol) and 1,6‐anhydro‐β‐D‐glucopyranose (levoglucosan, LG). Also, 2‐O‐TMS‐1,6‐anhydro‐β‐D‐glucopyranose, 4‐O‐TMS‐1,6‐anhydro‐β‐D‐glucopyranose and 2,4‐bis‐O‐TMS‐1,6‐anhydro‐β‐D‐glucopyranose were identified from the interpretation of electron impact and chemical ionisation mass spectra of products obtained from partially silylated levoglucosan solutions, together with information from the known relative reactivities of OH groups of anhydrosugars. A peak at m/z 116 was found to be characteristic of the mass spectra of partially silylated anhydrosugars, and is absent from the mass spectra of the persilylated species. Pyrolysis/GC/MS of cellulose in the presence of hexamethyldisilazane afforded principally the 2‐ and 4‐TMS ethers and the 2,4‐bis‐TMS ether of LG, whereas the 5‐TMS‐oxymethyl‐2‐furaldehyde was a prominent pyrolysis/silylation product of glucose. The mass spectra of other relevant pyrolysis/silylation products are presented. Copyright © 2002 John Wiley & Sons, Ltd.
Electrospray ionization quadrupole time‐of‐flight mass spectrometry and quadrupole mass spectrometry for genotyping single nucleotide substitutions in intact polymerase chain reaction products in K‐ras and p53
Authors: Muhammad Warees T. , Fox Karen F. , Fox Alvin , Cotham William , Walla Michael 
Published: December 2002

AbstractSingle nucleotide polymorphisms (SNPs) and mutations were genotyped for both homozygous and heterozygous PCR products of p53, a tumor suppressor gene, and K‐ras, an oncogene, using electrospray ionization (ESI) quadrupole time‐of‐flight (Q‐TOF) mass spectrometry (MS) and ESI‐quadrupole MS analysis. Mass accuracy was adequate for both instruments to detect genetic changes in homozygous PCR products, including the most difficult to distinguish (adenine [A] → thymine [T] transversion). However, for the detection of A → T shifts (9.0 Da difference) in heterozygous PCR products, the increased resolution of ESI‐Q‐TOFMS proved essential. Although, greater mass differences in heterozygotes (e.g. cytosine [C] ↔ T or guanine [G] ↔ A) can be discriminated using ESI‐quadrupole MS analysis. Copyright © 2002 John Wiley & Sons, Ltd.
Differentiation of the geographical origin of durum wheat semolina samples on the basis of isotopic composition
Authors: Brescia M. A. , Di Martino G. , Guillou C. , Reniero F. , Sacco A. , Serra F. 
Published: December 2002

AbstractThe identification of the geographical origin of foods is attracting great interest from consumers and producers since it may be used as a criterion for guaranteeing quality and authenticity. Stable isotope techniques can provide useful information on the origin of food products. The natural abundance isotopic ratios of carbon, oxygen and nitrogen were determined and a comparison made between the isotopic content of samples originating from Italy and those of samples originating from other countries (Canada, Turkey, Australia). A correlation was found between the isotopic composition and geographical origin of the samples. The relationship between isotopic content and the latitude has been confirmed. Copyright © 2002 John Wiley & Sons, Ltd.
Optimization of a liquid chromatography method based on simultaneous electrospray ionization mass spectrometric and ultraviolet photodiode array detection for analysis of flavonoid glycosides
Authors: Cuyckens Filip , Claeys Magda 
Published: December 2002

AbstractDifferent reversed‐phase liquid chromatography (LC) columns of conventional dimensions were coupled to an ultraviolet photodiode array detector (UV‐DAD) and a magnetic sector‐type spectrometer, equipped with an electrospray ionization (ESI) source, by a laboratory‐made flow splitter. A mixture of three flavonoid‐O‐glycosides was employed to examine the effects of the solvent composition, the flow rate, the stationary phase, the pH and the organic acid added, on the chromatographic separation, the UV‐DAD detection, the ESI process and the entire LC system with ESI‐MS and UV‐DAD detection. In the positive ion mode, methanol containing 1% acetic acid was by far the most sensitive in ESI‐MS analysis, whereas an acetonitrile/water mobile phase containing 0.5% formic acid was proved to give the best sensitivity in LC/ESI‐MS/UV‐DAD analysis. In the negative ion mode, the highest sensitivity was obtained with a mobile phase containing 0.1% formic acid, while addition of bases decreased the sensititvity. The optimal flow rate was higher in negative ESI (20–50 µL/min) than in positive ESI (5 µL/min), and the percentage of organic phase had an influence on the sensitivity of ESI‐MS detection. With regard to the selection of a suitable C18 reversed‐phase LC column, a column which is well end‐capped is to be preferred, because residual silanol groups appear to impair the separation of flavonoid glycosides. The optimized LC/ESI‐MS/UV‐DAD method was applied to a commercial Crataegus extract, which is used in phytomedicine to treat cardiovascular problems and is known to be rich in flavonoids. It is demonstrated how UV spectra and first‐order ESI mass spectra allow a fast characterization of flavonoids, even if reference compounds are not available or at hand. Copyright © 2002 John Wiley & Sons, Ltd.
Differentiation of vegetable oils by mass spectrometry combined with statistical analysis
Authors: Jakab A. , Nagy K. , Héberger K. , Vékey K. , Forgács E. 
Published: December 2002

AbstractThe main triacylglycerol (TAG) composition of different plant oils (almond, avocado, corn germ, grape seed, linseed, mustard seed, olive, peanut, pumpkin seed, sesame seed, soybean, sunflower, walnut and wheat germ) were analyzed using two different mass spectrometric techniques: HPLC/APCI‐MS (high‐performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry) and MALDI‐TOFMS (matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry).Linear discriminant analysis (LDA) as a multivariate mathematical statistical method was successfully used to distinguish different plant oils based on their relative TAG composition. With LDA analysis of either APCI‐MS or MALDI‐MS data, the classification among the almond, avocado, grape seed, linseed, mustard seed, olive, sesame seed and soybean oil samples was 100% correct. In both cases only 6 different oil samples from a total of 73 were not classified correctly. Copyright © 2002 John Wiley & Sons, Ltd.
Studies on azaspiracid biotoxins. II. Mass spectral behavior and structural elucidation of azaspiracid analogs
Authors: Brombacher Stephan , Edmonds Suzanne , Volmer Dietrich A. 
Published: December 2002

AbstractIn this report, the mass spectral analysis of azaspiracid biotoxins is described. Specifically, the collision‐induced dissociation (CID) behavior and differences between CID spectra obtained on a triple‐quadrupole, a quadrupole time‐of‐flight, and an ion‐trap mass spectrometer are addressed here. The CID spectra obtained on the triple‐quadrupole mass spectrometer allowed the classification of the major product ions of the five investigated compounds (AZA 1–5) into five distinct fragment ion groups, according to the backbone cleavage positions. Although the identification of unknown azaspiracids was difficult based on CID alone, the spectra provided sufficient structural information to allow confirmation of known azaspiracids in marine samples. Furthermore, we were able to detect two new azaspiracid analogs (AZA 1b and 6) in our samples and provide a preliminary structural analysis. The proposed dissociation pathways under tandem mass spectrometry (MS/MS) conditions were confirmed by a comparison with accurate mass data from electrospray quadrupole time‐of‐flight MS/MS experiments. Regular sequential MS
n analysis on an ion‐trap mass spectrometer was more restricted in comparison to the triple‐quadrupole mass spectrometer, because the azaspiracids underwent multiple [M + H − nH2O]+ (n = 1–6) losses from the precursor ion under CID. Thus, the structural information obtained from MS
n experiments was somewhat limited. To overcome this limitation, we developed a wide‐range excitation technique using a 180‐u window that provided results comparable to the triple‐quadrupole instrument. To demonstrate the potential of the method, we applied it to the analysis of degraded azaspiracids from mussel tissue extracts. Copyright © 2002 John Wiley & Sons, Ltd.
N‐Terminal peptide labeling strategy for incorporation of isotopic tags: a method for the determination of site‐specific absolute phosphorylation stoichiometry
Authors: Zhang Xiaolong , Jin Qian K. , Carr Steven A. , Annan Roland S. 
Published: December 2002

AbstractDetermining the phosphorylation stoichiometry at specific sites in a phosphoprotein is a very challenging task. We describe here a novel mass spectrometry based method that is capable of measuring the absolute phosphorylation stoichiometry at specific sites without the need for specific internal standards, phospho‐site antibodies or radioactivity. The method is based on a gentle chemical labeling strategy which specifically and differentially labels the N‐terminus of all peptides in a sample with either a D5‐ or D0‐propionyl group and measures the ratio of the abundance of the D5/D0 peptide pairs simultaneously using mass spectrometry. Using matrix‐assisted laser desorption/ionization (MALDI), the method can measure absolute stoichiometry to within at least 10% and can be applied to both in vitro and in vivo phosphorylated peptides and proteins. Furthermore, this method can potentially be applied to the quantitative study of other types of protein post‐translational modifications, and the profiling of protein expression on the proteome level. Copyright © 2002 John Wiley & Sons, Ltd.
A new sheathless electrospray interface for coupling of capillary electrophoresis to ion‐trap mass spectrometry
Authors: Bendahl Lars , Hansen Steen Honoré , Olsen Jørgen 
Published: December 2002

AbstractA simple laboratory‐made sheathless electrospray interface for coupling of capillary electrophoresis to ion‐trap mass spectrometry (CE/MS) was developed. The interface was machined in‐house and it was designed to be freely interchangeable with the commercially available ionization sources for the mass spectrometer. Sharpened fused‐silica capillaries were coated with nickel by a simple electrodeless plating procedure and were used as all‐in‐one columns/emitters. The electrodeless plating produced a 2–5‐µm thick smooth nickel layer that lasted for more than 8 h of continuous electrospraying. The performance of the CE/MS interface was examined by using four cationic imipramine derivatives as test substances. Relative detection limits were calculated on the basis of the extracted ion electrophorograms and were in the range 6–130 nmol/L, corresponding to absolute detection limits in the range of 20–400 amol. The system was applied for analysis of impurities in an impure imipramine N‐oxide preparation, and two of the impurities could be identified on the basis of online‐MS(MS) spectra recorded in scan‐dependent mode. Copyright © 2002 John Wiley & Sons, Ltd.
Structural confirmation of ostreocin‐D by application of negative‐ion fast‐atom bombardment collision‐induced dissociation tandem mass spectrometric methods
Authors: Ukena Takanori , Satake Masayuki , Usami Masaya , Oshima Yasukatsu , Fujita Tsuyoshi , Naoki Hideo , Yasumoto Takeshi 
Published: December 2002

AbstractNegative‐ion fast‐atom bombardment collision‐induced dissociation tandem mass spectrometric (FAB‐CID‐MS/MS) methodology was successfully applied to verify the highly complex structure of ostreocin‐D (MW 2633), a new palytoxin analog isolated from the marine dinoflagellate Ostreopsis siamensis and proposed to be 42‐hydroxy‐3,26‐didemethyl‐19,44‐dideoxypalytoxin based on NMR data. The charge‐remote fragmentations were facilitated by a negative charge introduced to a terminal amino group or to a hydroxyl group at the other terminus by a reaction with 2‐sulfobenzoic acid cyclic anhydride. Product ions generated from the [M − H]− ions provided information on the structural details of ostreocin‐D. Comparisons between the spectral data for ostreocin‐D and palytoxin also provided a rational basis for the assignments of product ions. Copyright © 2002 John Wiley & Sons, Ltd.
Reactions of lead cluster ions with acetone
Authors: Tian Zhixin , Xing Xiaopeng , Tang Zichao 
Published: December 2002

AbstractReactions of lead cluster cations and anions with acetone have been studied using a homemade reflectron time‐of‐flight mass spectrometer. Association with acetone to form Pbk(CH3COCH3)n+, high‐energy pathway reactions forming PbkCH3+, and intraheterocluster reaction of Pbk(CH3COCH3)n+1+ to give PbkCH3(CH3COCH3)n+ were the main reaction pathways for lead cluster cations with acetone. Decomposition of acetone by Pbk− to give PbkCm− ions and their further association with acetone, PbkCm(CH3COCH3)−, were the dominant reactions of lead cluster anions with acetone. Pb7−, Pb10−, and PbkC5− were ‘magic numbers’ with special structural stabilityin Pbk− and PbkCm−, respectively. In addition, PbkH−, CH2COCH3(CH3COCH3)n− and PbkCH2COCH3(CH3COCH3)n− were also observed in the reaction of lead cluster anions. Some reaction mechanisms are proposed for these reactions. To investigate the isotope effect for the reaction of lead cluster cations and anions with acetone and to verify the structural assignments of the observed ions, reactions of lead cluster cations and anions with deuterated acetone‐d6 were also performed. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of proanthocyanidins in grape seeds using electrospray mass spectrometry
Authors: Hayasaka Yoji , Waters Elizabeth J. , Cheynier Véronique , Herderich Markus J. , Vidal Stéphane 
Published: December 2002

AbstractTwo proanthocyanidin (PA) fractions, one (Sdp3) with the mean degree of polymerization (mDP) of 3 and the other (Sdp9) with mDP of 9, were obtained from a Vitis vinifera cv. Shiraz grape seed extract. The PA fractions were directly analyzed by electrospray ionization mass spectrometry (ES‐MS) and negative ion mass spectra were recorded. The mass spectrum of Sdp3 exhibited only singly charged ions corresponding to the molecular mass of PA with a degree of polymerization (DP) up to 9 (nonamers). In contrast, Sdp9 yielded rather complex mass spectra featuring ions with single [M − H]−, double [M − 2H]2− and triple [M − 3H]3− charge representing the molecular masses of PAs up to a DP of 28. In addition, the degree of galloylation per procyanidin (DG) was observed to be up to 5 (pentagallates) in Sdp3 and 8 (octagallates) in the Sdp9. This is the first evidence obtained by mass spectrometry for the distribution of grape seed PAs with such a high degree of polymerization and a broad diversity of galloylation. ES‐MS data together with the complementary information provided by acid hydrolysis provides a detailed picture of the composition of grape seed PAs. Copyright © 2002 John Wiley & Sons, Ltd.
Positive and negative gas‐phase ion chemistry of chlorofluorocarbons in air at atmospheric pressure
Authors: Bosa Elisabetta , Paradisi Cristina , Scorrano Gianfranco 
Published: December 2002

AbstractThis paper presents a report on the ionization/dissociation of some representative chlorofluoro‐carbons (CFCs) induced by corona discharges in air at atmospheric pressure. Both positive and negative ions formed from Freons 1,1,1‐trichlorotrifluoroethane (CFC 113a), 1,1,2‐trichlorotrifluoroethane (CFC 113), and 1,1,1,2‐tetrachlorodifluoroethane (CFC 112a) were analyzed using an atmospheric pressure chemical ionization mass spectrometry (APCI‐MS) instrument. Energy‐resolved mass spectra were obtained by modulating the kinetic energy of the ions via adjustment of the sampling cone potential (Vcone). Positive ion spectra of the CFCs (M) at low Vcone show no signals due to either M+· or MH+ but only those due to species [M − Cl]+ and CX3+ (X = Cl, F), likely formed via C–Cl and C–C bond cleavages following ionization via charge exchange. Charge localization in the products of C–C bond cleavage in M+· is driven by the stability of the neutral fragment. At low Vcone the hydrates [M − Cl]+(H2O) are also observed. In the case of 1,1,2,‐trichlorotrifluoroethane, [M − F]+ species also form as a result of ion‐molecule reactions. As Vcone is increased collision‐induced dissociation of [M − Cl]+ and [M − F]+, i.e., the perhalogenated cations C2X5+ (X = Cl, F), takes place via carbene elimination. In some cases such elimination is preceded or accompanied by rearrangements involving transfer of halogen from one carbon to the other. Evidence is also presented for the occurrence of a condensation reaction of C2Cl3F2+ with water to form a C2Cl2F2HO+ species via elimination of HCl. Negative ion spectra are dominated by Cl− and its ion‐neutral complexes with M and with water. Additional components of the plasma include ion‐neutral complexes O3−(M), the molecular anion M− (observed only with 1,1,2‐trichlorotrifluoroethane), and an interesting species corresponding to [M − Cl + O]−. The origin and structure of these [M − Cl + O]− species are discussed in terms of available thermochemical and reactivity data and current mechanistic views concerning reaction of O2− with halogenated compounds. The observation of both positive and negative ions containing oxygen is of special relevance to development of new processes for the treatment of volatile organic compounds (VOCs) based on oxidative decomposition induced by corona discharges in air at room temperature and pressure. Copyright © 2002 John Wiley & Sons, Ltd.
Characterisation of putative pentose‐containing conjugates as minor metabolites of 4‐bromoaniline present in the urine of rats following intraperitoneal administration
Authors: Major Hilary , Castro‐Perez Jose , Nicholson Jeremy K. , Wilson Ian D. 
Published: December 2002

AbstractThe metabolic fate of 4‐bromoaniline (4‐BrA) was investigated following intraperitoneal administration to the rat at 50 mg kg−1, using high‐performance liquid chromatography/time‐of‐flight tandem mass spectrometry (HPLC/TOF‐MS/MS). Up to five metabolites were detected in urine that correspond to isomeric pentose conjugates (possibly ribosides) of a hydroxysulphate of 4‐BrA. This identification is supported by further studies where the water used in the reversed‐phase solvent system was replaced with deuterated water in order to confirm that the number of exchangeable protons present in the metabolites was consistent with the proposed structures. Copyright © 2002 John Wiley & Sons, Ltd.
Analysis of ceramides in cosmetics by reversed‐phase liquid chromatography/electrospray ionization mass spectrometry with collision‐induced dissociation
Authors: Lee Myoung Hee , Lee Gae Ho , Yoo Jong Shin 
Published: December 2002

AbstractA rapid, sensitive and selective method involving reversed‐phase liquid chromatography (LC) with electrospray ionization (ESI) mass spectrometry (MS) was employed for determination of commercial ceramides in cosmetics for quality control of the product formulation. Using this LC/ESI‐MS technique, simultaneous separation and characterization of ceramides and an impurity substance were possible. Informative fragmentation patterns were obtained by employing LC/ESI‐MS in both positive and negative ionization modes to identify the structures of both sphingoid base and N‐acyl chains of ceramides, and also of an impurity. The combination of positive and negative mass spectra can be used for unambiguous confirmation of ceramides and for characterization of unknown species. In‐source collision‐induced fragmentation resulted in characteristic product anions for the ceramides containing a phytosphingosine moiety at m/z 267, 255 and 225, and for those with a sphingosine moiety at m/z 263 and 237, regardless of the length of the fatty acyl chains. The detection limit was about 0.5 pmol in selected‐ion monitoring mode. Quantification using internal standards showed good linearity and a relative standard deviation of 4%. These ceramides were more sensitively detected in positive than in negative ion mode. Copyright © 2002 John Wiley & Sons, Ltd.
Real Time Optimization for Robot Control using Receding Horizon Control with Equal Constraint
Authors: Takeuchi Hiroki 
Published: December 2002

AbstractThe equation to define a legged robot's ZMP (zero moment point) suggests a problem that ZMP cannot be obtained uniquely. This is because a redundancy exists in the equation which defines ZMP. Obtaining a true ZMP requires optimization calculation and this took a very long calculation time. We have to execute off‐line optimization beforehand. Then a real‐time control system follows these optimum trajectories which satisfy the ZMP condition. This is inconvenient for real‐time control of a robot. Carrying out a reduction of the equation so that it uniquely defines ZMP may assist in temporarily avoiding this problem. However, a pseudo ZMP is only able to be found. On the other hand, since RHC (receding horizon control), which is the new optimization technique, does not use a gradient method for optimization calculation, then it requires very little calculation time. This short time calculation such as sampling interval makes it possible to perform a real‐time calculation. However, RHC has not yet been applied to robot control. If an equality constraint can be set up in the formulation of RHC, it will be easy to apply to robot control. In this paper, it is proposed that RHC is used adding an equality constraint and then the formulation is performed. We discuss that the ZMP condition is used in the formulation using an equality constraint. Generally, it is difficult to take a ZMP variable as a state variable in a state equation. To ensure an optimal result, careful consideration of the ZMP conditions is required for the formulation. Then, this paper shows that the ZMP is defined as one of the input variables. Since ZMP input is obtained as an optimal solution, the technique proposed can generate a true ZMP trajectory on real time. Simulation results are performed by both the models in a two‐dimensional plane and the three‐dimensional space. This simple modeling enables an easy application to biped, quadruped and the other multiped robots. This simple modeling forms a basis for robot control. © 2003 Wiley Periodicals, Inc.
Obstacle Avoidance for Spatial Hyper‐Redundant Manipulators Using Harmonic Potential Functions and the Mode Shape Technique
Authors: Fahimi F. , Ashrafiuon H. , Nataraj C. 
Published: December 2002

AbstractThis paper deals with the obstacle avoidance problem for spatial hyper‐redundant manipulators in known environments. The manipulator is divided into two sections, a proximal section that has not entered the space among the obstacles and a distal section among the obstacles. Harmonic potential functions are employed to achieve obstacle avoidance for the distal section in three‐dimensional space in order to avoid local minima in cluttered environments. A modified panel method is used to generate the potential of any arbitrary shaped obstacle in three‐dimensional space. An alternative backbone curve concept and an efficient fitting method are introduced to control the trajectory of proximal links. The fitting method is recursive and avoids the complications involved with solving large systems of nonlinear algebraic equations. The combination of a three‐dimensional safe path derived from the harmonic potential field and the backbone curve concept leads to an elegant kinematic control strategy that guarantees obstacle avoidance. © 2003 Wiley Periodicals, Inc.