bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics and isotope patterns of ethanol and acetaldehyde emissions from yeast fermentations of glucose and glucose‐6,6‐d2 using selected ion flow tube mass spectrometry: a case study
Authors: Smith David , Wang Tianshu , S̆paněl Patrik 
Published: January 2005

AbstractAs a prelude to investigations of the emission of metabolites from human cell lines in vitro, we have conducted a study using selected ion flow tube mass spectrometry (SIFT‐MS) of the acetaldehyde and ethanol that appear in the headspace above a fermenting yeast/glucose/water mixture in sealed glass bottles at a temperature of 30 °C. A fixed quantity of yeast (10 mg) and varying amounts (2, 4, 8 and 16 mg) of both non‐deuterated glucose and glucose‐6,6‐d2 in 5 mL of water were used and the emission of the acetaldehyde and the ethanol were observed as a function of time. The ethanol and acetaldehyde concentrations in the headspace were obtained from the magnitudes of their characteristic ions on the accumulated SIFT mass spectra and, when the deuterated glucose was used, characteristic singly and doubly deuterated ions were obvious. This study indicates, as expected, that ethanol is the major species generated and that acetaldehyde is a relatively minor component of the headspace and a very minor component of the liquid phase. We estimate that about 108 ethanol molecules are produced per minute per cell in this yeast fermentation process. The distribution of the non‐deuterated and partially deuterated ethanol under these fermentation conditions is observed to be C2H5OH (66 ± 4)%, C2H4DOH(6 ± 1)%, C2H3D2OH(28 ± 4)%, and the analogous distribution for the acetaldehyde is the same, within error. These results indicate that the D atoms in the glucose‐6,6‐d2 are mostly retained by the 6‐C atom, but the appearance of the singly deuterated ethanol and acetaldehyde indicates that some D/H mixing must be occurring in the enzymatic reactions. The results of this study illustrate the potential and power of on‐line SIFT‐MS analysis in this area of research. Copyright © 2001 John Wiley & Sons, Ltd.
Derivatization for liquid chromatography/electrospray mass spectrometry: synthesis of tris(trimethoxyphenyl)phosphonium compounds and their derivatives of amine and carboxylic acids
Authors: Leavens William J , Lane Stephen J , Carr Richard M , Lockie Andrea M , Waterhouse Ian 
Published: January 2005

AbstractA simple method for the derivatization of primary amines and carboxylic acids with tris(trimethoxyphenyl)phosphonium (TMPP) reagents to enhance their detection by electrospray mass spectrometry (ESI‐MS) has been developed. The synthesis of novel TMPP reagents and their stable isotopically labelled analogues is described. Through the use of stable isotopically labelled TMPP ‘tags’, incorporation of a doublet (1:1, 1H/2H or 12C/13C) into the target molecule can be achieved, enabling the use of isotopic target analysis to detect compounds of unknown molecular weight but with a characteristic isotope pattern and accurate mass difference. Copyright © 2002 John Wiley & Sons, Ltd.
Dual parallel electrospray ionization and atmospheric pressure chemical ionization mass spectrometry (MS), MS/MS and MS/MS/MS for the analysis of triacylglycerols and triacylglycerol oxidation products
Authors: Byrdwell Wm. Craig , Neff William E. 
Published: January 2005

AbstractTwo mass spectrometers, in parallel, were employed simultaneously for analysis of triacylglycerols in canola oil, for analysis of triolein oxidation products, and for analysis of triacylglycerol positional isomers separated using reversed‐phase high‐performance liquid chromatography. A triple quadrupole mass spectrometer was interfaced via an atmospheric pressure chemical ionization (APCI) interface to two reversed‐phase liquid chromatographic columns in series. An ion trap mass spectrometer was coupled to the same two columns using an electrospray ionization (ESI) interface, with ammonium formate added as electrolyte. Electrospray ionization mass spectrometry (ESI‐MS) under these conditions produced abundant ammonium adduct ions from triacylglycerols, which were then fragmented to produce MS/MS spectra and then fragmented further to produce MS/MS/MS spectra. ESI‐MS/MS of the ammoniated adduct ions gave product ion mass spectra which were similar to mass spectra obtained by APCI‐MS. ESI‐MS/MS produced diacylglycerol fragment ions, and additional fragmentation (MS/MS/MS) produced [RCO]+ (acylium) ions, [RCOO + 58]+ ions, and other related ions which allowed assignment of individual acyl chain identities. APCI‐MS of triacylglycerol oxidation products produced spectra like those reported previously using APCI‐MS. APCI‐MS/MS produced ions related to individual fatty acid chains. ESI‐MS of triacylglycerol oxidation products produced abundant ammonium adduct ions, even for those molecules which previously produced little or no intact molecular ions under APCI‐MS conditions. Fragmentation (MS/MS) of the [M + NH4]+ ions produced results similar to those obtained by APCI‐MS. Further fragmentation (MS/MS/MS) of the diacylglycerol fragments of oxidation products provided information on the oxidized individual fatty acyl chains. ESI‐MS and APCI‐MS were found to be complementary techniques, which together contributed to a better understanding of the identities of the products formed by oxidation of triacylglycerols. Copyright © 2002 John Wiley & Sons, Ltd.
Structural isomer differentiation of 1,6‐diaza‐3,8‐dioxabicyclo[4.4.1]undecane and N,N′‐methylenebis(oxazolidine) by mass spectrometry
Authors: Monnier Valérie , Libot Francine , Aitken David J. , Husson Henri‐Philippe , Lesage Denis , Fournier Françoise , Tabet Jean‐Claude 
Published: January 2005

AbstractThe title compound types are structural isomers. The absence of literature studies dealing with the mass spectrometric gas‐phase behavior of such compounds prompted a search for the best conditions for differentiation between the two prototype examples (R,R)‐5,10‐diphenyl‐1,6‐diaza‐3,8‐dioxabi‐cyclo[4.4.1]undecane and N,N′‐methylenebis[(R)‐4‐phenyloxazolidine]. Attempts to differentiate between the isomers by NMR were inconclusive and X‐ray crystallography had to be used. The best mass spectrometric results were obtained using gas‐phase ionization techniques, particularly chemical ionization, whereby protonated molecules were observed. The fragmentation pathways were elucidated from MS/MS studies and from experiments performed on hexadeuterated samples of each compound. Copyright © 2002 John Wiley & Sons, Ltd.
Study of the neurotransmitter dopamine and the neurotoxin 6‐hydroxydopamine by electrospray ionization coupled with tandem mass spectrometry
Authors: Hao Chunyan , March Raymond E. , Croley Timothy R. , Chen Su , Legault M. Glenn , Yang Paul 
Published: January 2005

AbstractElectrospray ionization combined with tandem mass spectrometry has been applied to a study of dopamine and 6‐hydroxydopamine, an important neurotransmitter and a well‐known neurotoxin, respectively. Both protonated and deprotonated molecules were observed for the two compounds. Upon collision‐induced dissociation of protonated and deprotonated 6‐hydroxydopamine molecules, the number of fragmentation pathways observed was greater than that observed with protonated and deprotonated dopamine molecules; the greater proclivity to fragment of the former is due to the 6‐substituted hydroxyl group, which is para to the 3‐OH group and ortho to the CH2CH2NH2 group. Furthermore, 6‐hydroxydopamine showed a greater propensity to oxidize than did dopamine when sample solutions were kept uncovered in the air for 24 h prior to mass spectrometric examination. Radical structures of the four main oxidation products of 6‐hydroxydopamine have been suggested on the basis of their product ion mass spectra; one or more of these oxidation products may be responsible for the cytotoxic property of 6‐hydroxydopamine. Copyright © 2002 John Wiley & Sons, Ltd.
Ion dispersion near parallel wire grids in orthogonal acceleration time‐of‐flight mass spectrometry: predicting the effect of the approach angle on resolution
Authors: Lewin Mark , Guilhaus Michael , Wildgoose Jason , Hoyes John , Bateman Bob 
Published: January 2005

AbstractIons experience small deflections in the vicinity of grids in accelerators and ion mirrors in time‐of‐flight (TOF) mass spectrometers. Recent experiments with an orthogonal acceleration (oa) TOF instrument have verified that the effect can significantly degrade resolution when ions approach grids at an angle deviating from 90 °. The phenomenon becomes significant only when ions have components of velocity at right angles to the wires of the grids. A model is presented in this study to predict this phenomenon for parallel wire grids. The fractional energy spread of ions (calculated in the static TOF‐spectrometer frame of reference) scales directly with the approach angle of ions to the grid (as measured from normal approach). The energy spread also scales with the range of angles that is a consequence of the focusing effect in each gap between the wires of the grid. The equations imply that closely spaced parallel wire grids are best for deployment in oa‐TOF systems where non‐zero approach angles are unavoidable. Such grids are relatively impractical to manufacture and support but rectangular repeat cell grids with relatively few wires at right angles to the source axis are shown experimentally to introduce minimal energy spread. When these grids are rotated by 90 °, the resolution measured in a Q‐TOF spectrometer is degraded in approximate agreement with the parallel wire model. A practical implication of this work is that grid transmissions in oa‐TOF systems may be significantly increased without loss of resolution. Improvements of ∼200% (V‐mode) and ∼400% (W‐mode) in ion transmission were obtained in this study without compromising resolution. This was achieved with ∼73% transmission grids and greater potential improvements in transmission are being realised since this study with ∼89% transmission grids having similar geometry. Copyright © 2002 John Wiley & Sons, Ltd.
Pyrolysis‐gas chromatography/mass spectrometry of pitch fractions recovered from preparative size exclusion chromatography: structural differences with increasing molecular size
Authors: Islas C. A. , Suelves I. , Carter J. F. , Herod A. A. , Kandiyoti R. 
Published: January 2005

AbstractA sample of high‐temperature coal tar pitch has been fractionated by preparative scale size exclusion chromatography (SEC). Twenty‐four fractions corresponding to narrow molecular mass distributions were collected at sequential elution times of 3 minutes. The preparative scale column is thought to have filtered out most of the very large molecular mass material and the analysis focused on smaller mass components. The recovered fractions were characterised by analytical SEC. Pyrolysis‐gas chromatography/mass spectrometry (pyrolysis‐GC/MS) of the fractions was used to evaluate changes in main structural features with changing molecular size.As expected, analytical SEC of the fractions showed a systematic shift to smaller molecular sizes with increasing elution time. UV‐fluorescence spectra of the samples showed parallel structural shifts to shorter wavelengths and gains in intensity with increasing elution times. Pyrolysis‐GC/MS showed parent polycyclic aromatic components considered typical of pitch. The major fragments detected were pyrenes and fluoranthenes (m/z 202) and chrysenes (m/z 228). Benzopyrenes (m/z 252) and larger aromatics were not prominent amongst the pyrolysis products. Taken together, molecular structures were found to change significantly from fraction to fraction, but no systematic pattern emerged with changing elution time. Some components were identified as having formed during the analytical pyrolysis procedure itself. As aromatic products larger than dibenzopyrene (m/z 302) would not elute from the column, detected fragments are thought to have detached from larger pitch molecules.The pyrolysis of the largest species gave only alkanes and alkenes, with the aromatic fragments thought to be too large to elute through the GC column. The work provides information regarding the aromatic groups that are readily lost from larger molecules. Larger aromatic structures are thought to condense (to char) during the analytical pyrolysis step; the method is limited in not being able to provide information about their structural features. Copyright © 2002 John Wiley & Sons, Ltd.
Direct analysis of highly oxidised organic aerosol constituents by on‐line ion trap mass spectrometry in the negative‐ion mode
Authors: Warscheid Bettina , Hoffmann Thorsten 
Published: January 2005

AbstractOn‐line ion trap mass spectrometry (ITMS) enables the characterisation of constituents of biogenic secondary organic aerosols in complex organic reaction mixtures. This real‐time analysis is achieved by directly introducing the airborne particles into the ion source of the mass spectrometer. Negative‐ion chemical ionisation at atmospheric pressure (APCI(−)) was used as the ionisation method of choice. The aerosols were generated from the gas‐phase ozonolysis of two C10H16‐terpenes (α‐pinene and limonene), and investigated by performing on‐line APCI(−)−ITMSn. Highly oxidised compounds were tentatively identified as important particle‐phase products. Based on recent investigations of low‐energy collision‐induced dissociation pathways of a wide range of deprotonated multifunctional carboxylic acid species derived from monoterpene precursors (Warscheid B, Hoffmann T. Rapid Commun. Mass Spectrom. 2001; 15: 2259), the formation of structurally different C10H16O5 and C10H16O6 species, such as acidic esters from α‐pinene and aldo‐hydroxycarboxylic acids from limonene, is proposed. Copyright © 2002 John Wiley & Sons, Ltd.
High accuracy mass measurement of peptides with internal calibration using a dual electrospray ionization sprayer system for protein identification
Authors: Zhou Feng , Shui Wenqing , Lu Yu , Yang Pengyuan , Guo Yinlong 
Published: January 2005

AbstractA dual‐ESI‐sprayer system was constructed and applied to achieve high accuracy of peptide mass measurement for protein identification by means of peptide mapping. Sample was introduced in one sprayer, and reference in the other, thus making internal calibration possible greatly enhancing the mass accuracy. Several samples were utilized to evaluate the reliability of this dual‐ESI‐sprayer system. The range of mass errors was 0.16–5.37 ppm. The peptide masses of tryptic digests of myoglobin (horse) were measured by the HPLC/dual‐ESI‐MS system, with mass deviations ranging from 0.01–7.67 ppm, and about 75% mass deviations below 5 ppm with 40% below 1 ppm. These peptide masses were utilized to perform database searching for protein identification, and compared to results obtained by external calibration. This comparison showed that the internal calibration provides a more reliable method of protein identification, with a much smaller number of required peptides for matching, and with less CPU time consumed for database searching. Copyright © 2002 John Wiley & Sons, Ltd.
Novel phosphoryl derivatization method for peptide sequencing by electrospray ionization mass spectrometry
Authors: Chen Jing , Chen Yi , Gong Peng , Jiang Yang , Li Yan‐Mei , Zhao Yu‐Fen 
Published: January 2005

AbstractA one‐step phosphoryl derivatization method has been used in a peptide sequencing procedure for electrospray ionization tandem mass spectrometry (ESI‐MS/MS). The sodiated derivatized peptides exhibit very simple dissociation patterns, in which two kinds of fragment ions, [bn + OH + Na]+ and [an + Na]+, are formed. Since the amino acid residues are lost sequentially from the C‐terminus, peptide sequences can be identified easily. The fragmentation efficiency of peptides increased as a result of the phosphorylation, and also provided peaks of useful intensity at lower m/z. A peptide with lysine at the C‐terminus was derivatized and analyzed by ESI‐MS/MS. Similar mass spectra, from which the sequence could be read out, were obtained. This is a novel derivatization method yielding neutral derivatives that should be suitable for peptide sequencing by LC/ESI‐MS/MS. Copyright © 2002 John Wiley & Sons, Ltd.
Improved method for the simultaneous determination of d4T, 3TC and ddl intracellular phosphorylated anabolites in human peripheral‐blood mononuclear cells using high‐performance liquid chromatography/tandem mass spectrometry
Authors: Becher François , Pruvost Alain , Goujard Cécile , Guerreiro Catherine , Delfraissy J.‐F. , Grassi Jacques , Benech Henri 
Published: January 2005

AbstractThere is still a need for direct determination (i.e. without dephosphorylation) of nucleoside reverse transcriptase inhibitor (NRTI) triphosphorylated nucleotides in the peripheral‐blood mononuclear cells (PBMCs) of HIV‐positive patients. The objective of this paper was first to improve our previously described direct liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay for stavudine triphosphate (d4T‐TP). Preparation of PBMCs was modified to reduce degradation of d4T‐TP during cell preparation and to simplify this step for routine use in clinical units. The performance of several HPLC columns was compared in order to improve the stability of peak shape over time. The SMT C18 column was replaced by a Supelcogel ODP‐50, thereby reducing two‐fold the concentration of the first standard. Various internal standards were compared to optimize peak shape and remove an interfering peak in LC. 2‐Chloroadenosine 5′‐triphosphate was chosen as the most appropriate internal standard. Substitution of the narrowbore column by a microbore column (150 × 0.32 mm) is also presented and discussed. Secondly, this improved method was successfully applied to the simultaneous determination of d4T‐TP, dideoxyadenosine triphosphate (ddA‐TP) and lamivudine triphosphate (3TC‐TP) in PBMCs, which is useful in view of the common use of NRTI combinations. The method was subsequently applied to clinical samples from HIV‐positive patients receiving antiretroviral therapy containing d4T, ddl and/or 3TC. This method can be used simply and routinely on approximately 200 samples per week, using commercially available instruments and with a simple cell lysis as sample treatment. Copyright © 2002 John Wiley & Sons, Ltd.
A new linear ion trap mass spectrometer
Authors: Hager James W. 
Published: January 2005

AbstractCharacteristics of mass selective axial ion ejection from a linear quadrupole ion trap in the presence of an auxiliary quadrupole field are described. Ion ejection is shown to occur through coupling of radial and axial motion in the exit fringing fields of the linear ion trap. The coupling is efficient and can result in extraction of as much as 20% of the trapped ions. This, together with the very high trapping efficiencies, can yield high sensitivity mass spectral responses. The experimental apparatus is based on the ion path of a triple quadrupole mass spectrometer allowing either the q2 collision cell or the final mass analysis quadrupole to be used as the linear trap. Space charge induced distortions of the mass resolved features while using the pressurized q2 linear ion trap occur at approximately the same ion density as reported for conventional three‐dimensional ion traps. These distortions are, however, much reduced for the lower pressure linear trap possibly owing to the proposed axial ejection mechanism that leads to ion ejection only for ions of considerable radial amplitude. RF heating due to the high ejection q‐value and the low collision frequency may also contribute. Two hybrid RF/DC quadrupole‐linear ion trap instruments are described that provide high sensitivity product ion scanning while operated in the linear ion trap mode while also retaining all conventional triple quadrupole scan modes such as precursor ion and neutral loss scan modes. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of rare earth elements in urine by electrothermal vaporization inductively coupled plasma mass spectrometry
Authors: Bettinelli Maurizio , Spezia Sandro , Terni Cesarina , Ronchi Anna , Balducci Claudio , Minoia Claudio 
Published: January 2005

AbstractA method was developed for the determination of rare earth elements (REEs) in urine with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV‐ICPMS). The undiluted sample was directly injected into the graphite tube and trifluoromethane (Freon‐23) was used as chemical modifier in order to reduce the vaporization temperature and the memory effect of most of the lanthanides. The detection limits were in the range 1–10 ng/L with relative standard deviation of 3–5% at concentration levels of 1µg/L, and less than 10–15% at 100 ng/L. Two different procedures, external calibration and a standard additions method, were evaluated to measure the concentration levels of lanthanides in the urine samples and the second procedure was considered to be the best choice for calibration in this work. The level of REEs in urine of 50 healthy volunteers was in the range 5–20 ng/L, above the detection limit of ETV‐ICPMS. Copyright © 2002 John Wiley & Sons, Ltd.
A straightforward means of coupling preparative high‐performance liquid chromatography and mass spectrometry
Authors: Cai Hong , Kiplinger Jeffrey P. , Goetzinger Wolfgang K. , Cole Roderic O. , Laws Kathrine A. , Foster Marc , Schrock Audrey 
Published: January 2005

AbstractFlow splitting to a mass spectrometer is a common way of coupling a highly specific detector to preparative or semi‐preparative high‐performance liquid chromatography (HPLC) purification of combinatorial libraries, drug metabolites, and characterizable impurities. The sensitive mass spectrometer consumes only a small fraction of the analyte while providing online structure‐specific detection, and its output can thus be used to trigger collection of the desired fraction. Coupling mass spectrometry to preparative HPLC is difficult due to the susceptibility of the detector to fouling under conditions of high analyte concentration or solute amount, or to changes in solvent composition. We report here on a device, the mass rate attenuator (MRA), which automatically produces split ratios over a range of 100:1 to 100 000:1 under programmable user control. The MRA is a flow‐control device that periodically gates a small aliquot from one liquid stream into another. The design allows the user to set the frequency of the gating without interruption of the HPLC flow stream. The MRA also allows control of the volume of the aliquot that is transferred between the flow streams. This additional control, compared to passive splitting devices, facilitates optimization of the tubing connecting the separation, detection and collection events. We demonstrate that such optimization can reduce the volume of the collected fraction without compromising recovery, thus reducing the time spent in evaporating solvents to reclaim purified products. Copyright © 2002 John Wiley & Sons, Ltd.
Detecting aristolochic acids in herbal remedies by liquid chromatography/serial mass spectrometry
Authors: Kite Geoffrey C. , Yule Marianne A. , Leon Christine , Simmonds Monique S. J. 
Published: January 2005

AbstractTargeted liquid chromatography/serial mass spectrometry (LC/MS/MS) analysis, using a quadrupole ion‐trap mass spectrometer, permitted the detection of aristolochic acids I and II in crude 70% methanol extracts of multi‐component herbal remedies without any clean‐up or concentration stages. The best ionisation characteristics were obtained using atmospheric pressure chemical ionisation (APCI) and by including ammonium ions in the mobile phase. Limits of detection for aristolochic acids were influenced by the level of interference created by other components in the sample matrix. They were determined to be between 250 pg and 2.5 ng on‐column within a matrix containing compounds extracted from 2 mg of herbal remedy. With a herbal remedy that only permitted the higher limit of detection, this sensitivity was sufficient to detect the aristolochic acids extracted from 0.1% dry weight of Aristolochia manshuriensis included in the preparation. Copyright © 2002 John Wiley & Sons, Ltd.