bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxygen isotopes in nitrate: new reference materials for 18O:17O:16O measurements and observations on nitrate‐water equilibration
Authors: Böhlke J. K. , Mroczkowski S. J. , Coplen T. B. 
Published: July 2003

AbstractDespite a rapidly growing literature on analytical methods and field applications of O isotope‐ratio measurements of NO3− in environmental studies, there is evidence that the reported data may not be comparable because reference materials with widely varying δ18O values have not been readily available. To address this problem, we prepared large quantities of two nitrate salts with contrasting O isotopic compositions for distribution as reference materials for O isotope‐ratio measurements: USGS34 (KNO3) with low δ18O and USGS35 (NaNO3) with high δ18O and ‘mass‐independent’ δ17O. The procedure used to produce USGS34 involved equilibration of HNO3 with 18O‐depleted meteoric water. Nitric acid equilibration is proposed as a simple method for producing laboratory NO3− reference materials with a range of δ18O values and normal (mass‐dependent) 18O:17O:16O variation. Preliminary data indicate that the equilibrium O isotope‐fractionation factor (α) between [NO3−] and H2O decreases with increasing temperature from 1.0215 at 22°C to 1.0131 at 100°C. USGS35 was purified from the nitrate ore deposits of the Atacama Desert in Chile and has a high 17O:18O ratio owing to its atmospheric origin. These new reference materials, combined with previously distributed NO3− isotopic reference materials IAEA‐N3 (=IAEA‐NO‐3) and USGS32, can be used to calibrate local laboratory reference materials for determining offset values, scale factors, and mass‐independent effects on N and O isotope‐ratio measurements in a wide variety of environmental NO3− samples. Preliminary analyses yield the following results (normalized with respect to VSMOW and SLAP, with reproducibilities of ±0.2–0.3‰, 1σ): IAEA‐N3 has δ18O = +25.6‰ and δ17O = +13.2‰; USGS32 has δ18O = +25.7‰; USGS34 has δ18O = −27.9‰ and δ17O = −14.8‰; and USGS35 has δ18O = +57.5‰ and δ17O = +51.5‰. Published in 2003 by John Wiley & Sons, Ltd.
Thermometer ions for matrix‐enhanced laser desorption/ionization internal energy calibration
Authors: Greisch J.‐F. , Gabelica V. , Remacle F. , De Pauw E. 
Published: July 2003

AbstractThis work describes a method to use relative fragmentation yields to characterize the internal energy distribution of ions produced by matrix‐enhanced laser desorption/ionization mass spectrometry (MELDI‐MS, see: Wright LG, Cooks RG, Wood KL. Biomed. Mass Spectrom. 1985; 12: 153–162). Assuming that the fragmentation proceeds statistically and that the collisions in the source lead to a Boltzmann‐like distribution of the internal energy, a characteristic parameter, the effective temperature, is introduced to describe the internal energy distribution of the ions observed. The hypotheses, advantages and drawbacks of the implementation of the method that uses substituted benzylpyridinium salts as thermometer ions are discussed. Use is made of two matrices that produce no matrix cations in MELDI and are suitable for small cationic salts. The actual value of this effective temperature significantly depends on an accurate determination of the threshold dissociation energies and on the time spent in the source, in addition to the statistical hypothesis itself. The method could be applied to normalize spectra in order to compare results issued from different instruments. Published in 2003 by John Wiley & Sons, Ltd.
High‐performance liquid chromatography/inductively coupled plasma mass spectrometry with iodine‐specific detection for profiling the metabolites produced in the earthworm Eisenia veneta by exposure to 2‐fluoro‐4‐iodoaniline
Authors: Duckett Catherine J. , Wilson Ian D. , Walker Heather , Abou‐Shakra Fadi , Lindon John C. , Nicholson Jeremy K. 
Published: July 2003

AbstractHigh‐performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC/ICPMS) provided a rapid and specific means for profiling the iodine‐containing metabolites produced by the earthworm Eisenia veneta following exposure to 2‐fluoro‐4‐iodoaniline. Profiles were obtained, using gradient reversed‐phase HPLC, from extracts of whole earthworms and from coleomic fluid with as little as 25 ng/peak of iodine detected. The use of ICPMS in this way provides a convenient means of determining the metabolic fate of iodinated compounds without the need for radiolabelled compounds. Copyright © 2003 John Wiley & Sons, Ltd.
A simple and rapid method for identifying the source of spilled oil using an electronic nose: confirmation by gas chromatography with mass spectrometry
Authors: Tzing Shin‐Hwa , Chang Jia‐Yaw , Ghule Anil , Chang Jia‐Jiu , Lo Bertrand , Ling Yong‐Chien 
Published: July 2003

AbstractTwo types of electronic nose (EN), different in operational principle, were used to identify the source of spilled oil in an accident. The suspected sources considered were petroleum oil reservoirs and pipelines located near the site of the accident. Gas chromatography/mass spectrometry (GC/MS), operated in both EI and CI modes, was employed to confirm the identified source. The advantage of multisensors in spatially resolved sensing for direct multicomponent analysis was explored to minimize tedious sample preparation procedures. Subsequent principal component analysis helped in identifying the source. The advantage of fast separation in temporally resolved sensing was explored to rapidly yield compositional information; the resulting graphical representations helped clarify the source. Traditional GC/MS not only confirms the identified spilled oil source, but also provides detailed diagnostic information such as total petroleum hydrocarbons, polycyclic aromatic hydrocarbons and their C1–C4 alkylated homologues, as well as the n‐alkanes, which are essential for follow‐up remedial and regulatory actions. The main use of the electronic nose was demonstrated to be as a simple and rapid screening method for identifying a spilled oil source. Copyright © 2003 John Wiley & Sons, Ltd.
Determination of coplanar and non‐coplanar polychlorinated biphenyls in human serum by gas chromatography with mass spectrometric detection: electron impact or electron‐capture negative ionization?
Authors: Turci Roberta , Bruno Franco , Minoia Claudio 
Published: July 2003

AbstractA time‐ and cost‐saving method for the congener‐specific analysis of polychlorinated biphenyls (PCBs) in human serum has been developed and validated. After two fast extraction and clean‐up steps, analyses were performed using gas chromatography coupled with mass spectrometry with single ion monitoring (GC/SIM‐MS), either in electron impact (EI) or electron‐capture negative ionization (ECNI) mode. For the determination of dioxin‐like congeners, an improvement in EI‐MS sensitivity is desirable and use of NI is thus preferred. The procedure was validated for 12 dioxin‐like congeners by analyzing spiked samples on three different days and using 13C12‐labelled analogues as internal standards. When using an NCI source, the limit of quantification was assessed at 0.01 μg/L, except for PCBs #77 and #81, which cannot be reliably detected below 0.05 μg/L. For the lower chlorinated non‐dioxin‐like congeners, NI offers less selectivity because of limited fragmentation. Electron impact ionization and electron‐capture negative ionization mode can therefore be considered to be complementary for the determination of PCB congeners in the general population. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of the metal‐binding selectivity of the metallochaperone CopZ from Enterococcus hirae by electrospray ionization mass spectrometry
Authors: Urvoas Agathe , Amekraz Badia , Moulin Christophe , Le Clainche Loïc , Stöcklin Reto , Moutiez Mireille 
Published: July 2003

AbstractMetallochaperones are soluble proteins involved in metal transport and regulation in vivo. Copper metallochaperones belong to a structural family of metal binding domains displaying a ferredoxin‐like fold (βαββαβ) and a consensus metal‐binding motif MXCXXC. The metal‐binding selectivities for this class of proteins are poorly documented so far. The present study focuses on the measurement of the selectivity of the copper metallochaperone CopZ from Enterococcus hirae for different metal ions using an experimental approach based on electrospray ionization mass spectrometry (ESI‐MS). All the metal cations tested, i.e. Cu(I), Cu(II), Hg(II), Cd(II) and Co(II), form specific metal complexes with CopZ. The study of a chemically modified CopZ as well as variants of CopZ in the active site demonstrated that the complexes observed by ESI‐MS, i.e. in the gas phase, corresponded to the complexes previously observed by other analytical methods in solution. Competition experiments allowed the classification of the metal ions by increasing affinities for CopZ as follows: Co ≪ Cd < Hg < Cu. A dissociation constant in the range of 20 μM was determined for cobalt. The affinity of CopZ for the other metals tested was found to be higher, with dissociation constants smaller than micromolar. Copyright © 2003 John Wiley & Sons, Ltd.
Sonic spray ionization applied to liquid chromatography/mass spectrometry analysis of endocrine‐disrupting chemicals in environmental water samples
Authors: Benijts Tom , Günther Wolfgang , Lambert Willy , Leenheer André De 
Published: July 2003

AbstractA sonic spray ionization liquid chromatography/mass spectrometry (LC/SSI‐MS) procedure combined with off‐line solid‐phase extraction was optimized for the analysis of 20 endocrine‐disrupting chemicals (EDCs) in water samples. Method development included a comparison of the novel sonic spray ionization (SSI) with more traditional ion sources, i.e. pneumatically assisted electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). It was demonstrated that SSI and ESI spectra were very similar, but were more prone to the formation of solvent cluster ions as compared with APCI spectra. This phenomenon was most prominent for SSI and resulted in an increased chemical background in full‐scan mass spectra. However, this chemical noise did not affect the overall sensitivity of SSI and ESI. After optimization of LC and MS parameters, the LC/SSI‐MS method was validated. Recoveries ranged from 76.3 up to 113.4% for all compounds. Limits of detection (LOD) and quantitation (LOQ) were established between 3.0 and 11.5 ng/L and 9.9 and 38.0 ng/L, respectively. Within‐day (n = 5) and between‐day (n = 5) reproducibility were investigated at three levels and ranged from 3.3–16.5% and 7.6–19.2%, respectively. Eight‐point calibration curves were established and showed linearity for all compounds (r2 > 0.987) over a linear dynamic range of 10–10 000 ng/L. Copyright © 2003 John Wiley & Sons, Ltd.
Gas chromatography/isotope‐ratio mass spectrometry method for high‐precision position‐dependent15N and18O measurements of atmospheric nitrous oxide
Authors: Röckmann Thomas , Kaiser Jan , Brenninkmeijer Carl A. M. , Brand Willi A. 
Published: July 2003

AbstractWe describe an automated gas chromatography/isotope‐ratio mass spectrometry (GC/IRMS) method for the determination of the18O and position‐resolved15N content of nitrous oxide at natural isotope abundance. The position information is obtained from successive measurement of the isotopic composition of the N2O+ion atm/z44, 45, 46 and the NO+fragment ion atm/z30, 31. The fragment ion analysis is complicated by a non‐linearity in the mass spectrometer that has to be taken into account. Evaluation of the absolute peak areas allows for a simultaneous determination of the N2O mixing ratio for atmospheric samples. Samples with mixing ratios ranging from a few nmol/mol up to the percent level can be analyzed using different sample inlet systems. The high concentration inlet system provides an easy and quick method to carry out various diagnostic tests, in particular to perform realistic linearity tests. A gas chromatographic set‐up with a split column and a backflush possibility improves analytical precision and excludes interferences by substances with long retention times from preceding runs. We also describe a new open split interface that uses only a single transfer capillary to the mass spectrometer for sample and reference gas. Copyright © 2003 John Wiley & Sons, Ltd.
Development of a liquid chromatography/tandem mass spectrometry assay for the quantification of Aplidin®, a novel marine‐derived antineoplastic agent, in human plasma
Authors: Yin Jianming , Aviles Pablo , Lee William , Ly Carl , Floriano Pablo , Ignacio Manzanares , Faircloth Glynn 
Published: July 2003

AbstractA rapid and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay was developed and validated to quantify a novel marine‐derived depsipeptide, Aplidin®, in human plasma. The method was validated to demonstrate the specificity, recovery, limit of quantitation (LOQ), accuracy, and precision of measurements. The calibration range for Aplidin® was established using Aplidin® standards from 0.05–50 ng/mL in blank human plasma. The multiple reaction monitoring, based on the transition m/z 1110.7 → 295.3, was specific for Aplidin®, and that based on the transition m/z 1112.6 → 297.3 was specific for didemnin B (the internal standard); no endogenous materials interfered with the analysis of Aplidin® and didemnin B from blank human plasma. The assay was linear over the concentration range 0.05–50.0 ng/mL. The correlation coefficients for the calibration curves ranged from 0.9979 to 0.9999. The mean intra‐ and interday accuracies for all calibration standards (n = 12) ranged from 97 to 106% (≤6% bias), and the mean interday precision for all calibration standards was less than 8.3%. The mean intra‐ and interday assay accuracy for all quality control replicates (n = 12), determined at each QC level throughout the validated runs, remained below 12 and 7%, respectively. The mean intra‐ and interday assay precision was less than 13.1 and 10.7% for all QC levels, respectively. The assay is currently used to measure Aplidin® plasma concentrations to support clinical trials. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of oxidized epigallocatechin gallate by liquid chromatography/mass spectrometry
Authors: Mizooku Yasuo , Yoshikawa Muneyoshi , Tsuneyoshi Toshihiro , Arakawa Ryuichi 
Published: July 2003

Abstract(−)‐Epigallocatechin gallate (EGCG) of catechins changes from non‐colored at around neutral pH to yellow at higher pH region in aqueous solution. The pH‐dependent oxidation of EGCG was analyzed by liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS). LC/MS/MS analysis of EGCG and its related compounds, (−)‐epicatechin gallate (ECG) and (−)‐epigallocatechin (EGC), successfully elucidated the structure relationship of EGCG solution involving the color change reaction at different pH conditions. The oxidation species produced at alkaline pH was detected at a different retention time from EGCG in the chromatograms of the EGCG sample. The oxidation species was found to correspond to M+14 (where M is the molecular weight of EGCG), which has two hydrogen atoms removed and addition of one oxygen atom to the gallyl moiety in the B‐ring of EGCG. Copyright © 2003 John Wiley & Sons, Ltd.
Generation of experimental L x‐ray fluorescence cross‐sections for inter‐elements at inter‐energies EL1 ≤ E ≤ EK (computer program IGELCS)
Authors: Mittal Raj , Singh Meenu , Vandana  
Published: July 2003

AbstractThe experimental values of L x‐ray fluorescence (XRF) cross‐sections are not available for all the elements in the range La–U, at all the photon energies E in the range EL1 ≤ E ≤ EK. To generate L XRF cross‐sections, where experimental measurements are not available, two empirical relations have been developed, one between the L XRF cross‐sections and photon energy and the other between the L XRF cross‐sections and atomic number. For the measured data on L XRF cross‐sections at incident energies between Ll and K edges of an element and the data on L XRF cross‐sections for elements in the range 57 ≤ Z ≤ 92 at an energy value, polynomial fits have been derived. The L XRF cross‐section values generated with the derived empirical relations were found to be in agreement with the experimental values within their experimental uncertainties. Subsequently, a software code IGELCS was developed to interpolate and to generate the cross‐sections at inter‐energies and for inter‐elements in a single computer run. The running of the software requires minimum input data on five elements at five common energies. Copyright © 2003 John Wiley & Sons, Ltd.
Compton scattering of 59.54 keV γ‐rays from Fe and p‐Si samples in an external magnetic field
Authors: Şahin Yusuf , Demir Demet 
Published: July 2003

AbstractWe report on the Compton scattering of photons from samples whose surface charge density distributions are changed by an external magnetic field. We performed a Compton scattering experiment known to be particularly sensitive to the behavior of the relatively slower moving outer electrons (valence electrons) involved in bonding in condensed matter. The external magnetic field was used to change the surface charge density distributions of Fe and p‐Si samples. Samples were located in the external magnetic field of intensity 215 G and in a direction which was perpendicular both to the current and surface of the samples bombarded by 59.5 keV γ‐photons emitted from an Am‐241 point source. Currents in the ranges 0–8.5 A and 0–300 µA were applied to the Fe and p‐Si samples, respectively. The Compton scattered photons at an angle of 100° were detected by an Si(Li) detector. It was observed that the counts acquired under the Compton peaks tended to decrease linearly with increasing current in a magnetic field. The results show that positive charge carriers behave like negative charge carriers and electrons are more effective than holes in the Compton scattering of γ‐rays. Copyright © 2003 John Wiley & Sons, Ltd.
Evaluation of the uncertainty of element determination using the energy‐dispersive x‐ray fluorescence technique and the emission–transmission method
Authors: Wegrzynek D. , Markowicz A. , Chinea‐Cano E. , Bamford S. 
Published: July 2003

AbstractA detailed study of the uncertainty quantification procedure for the determination of element mass fractions in a soil matrix by using energy‐dispersive x‐ray fluorescence spectrometry and the emission–transmission method was carried out. The particular case of secondary target excitation with an Mo target and Mo anode x‐ray tube was addressed. The effects of simplification of the theoretical model on the determined mass fractions of elements were studied. The main contributions to the uncertainty were identified and the ways of reducing their magnitude were indicated. The approach was found to be helpful in designing an optimum analytical strategy. It can also be used as guidance for assessing the uncertainty in other modes of x‐ray fluorescence analysis. Copyright © 2003 John Wiley & Sons, Ltd.
Selective excitation and integral counting of x‐ray fluorescence (SEICXRF)
Authors: Figueroa R. 
Published: July 2003

AbstractThis paper proposes a spectrometric method for x‐ray fluorescence, based on selective excitation and integral counting of the emitted photons by the sample. It is named SEICXRF (Selective Excitation and Integral Counting of X‐Ray Fluorescence). The general characteristics of the method are shown: the spectrometer, the spectrum acquisition, the effects involved in the determination of the jump intensity and their respective algorithms (the primary and secondary intensities and other unexpected effects), its capacity to identify elements, its sensitivity, its limitations and scope. Copyright © 2003 John Wiley & Sons, Ltd.
Algorithm of fundamental parameters for the SEICXRF method
Authors: García M. , Figueroa R. , Rivera R. 
Published: July 2003

AbstractAn algorithm based on fundamental parameters and applied to the SEICXRF method, developed by one of the authors, is presented. The methodology used in the calculation is similar to the Rousseau fundamental parameters method, but the main difference is the considerations about the x‐ray secondary fluorescence. In the new experimental method, the fluorescence yield by photons corresponding to the absorption edges with energies greater than the absorption edge energy of analyte does not occur. This secondary fluorescence appears in the calculation of the total fluorescence as a consequence of the integral count of the fluorescent emission from the sample. It is created by the primary fluorescence yield of the atoms whose absorption edge energies are less than the primary fluorescence energy of the analyte. The algorithm also considers the effect of the decrease of the sample fluorescent background just at the jump, originated by the change of the absorption coefficient at the absorption edge energy of the element of interest. Considering these two effects, including the primary fluorescence in the calculation, allows one to obtain the net fluorescence originated by the analyte at its own absorption edge. Copyright © 2003 John Wiley & Sons, Ltd.
Comparison between intensity jumps in experimental, simulated and theoretical multielemental spectra
Authors: Figueroa R. , García M. , Brusa D. 
Published: July 2003

AbstractThe results obtained by applying the theory developed for the SEICXRF method and applying a Monte Carlo simulation code (MCS) are compared with the experimental data in order to validate this theory. Specifically, an assay is made with the spectra corresponding to a brass sample and a soil sample. The experimental data were corrected considering the chamber efficiency and the dead time of the detection system. The considerations taken into account in order to obtain a correct comparison between theory and experiment are discussed in detail. Good agreement between spectra is observed, taking as reference the given values of the elemental composition. The experimental intensity jumps are in agreement with those predicted by the theory and by the MCS. Copyright © 2003 John Wiley & Sons, Ltd.
An investigation of x‐ray escape for an HPGe detector
Authors: Can Cüneyt , Bilgici Serdar Ziya 
Published: July 2003

AbstractX‐ray escape peaks for a planar HPGe detector were investigated for a point source of photons with 59.5 keV energy. The effect of the solid angle for the incident photons on the escape probability of Ge K x‐rays was studied using collimators with varying apertures. A Monte Carlo program was also developed to estimate the probability of escape for various mechanisms and routes. The experimental and simulation results showed that the escape probability is essentially constant for a wide range of collimator radii, but at first starts to increase and then becomes constant when the side surface of the detector becomes accessible for escape with larger collimators. Copyright © 2003 John Wiley & Sons, Ltd.
Escape of photoelectrons and Compton‐scattered photons from an HPGe detector
Authors: Can Cüneyt 
Published: July 2003

AbstractThe response function of a planar HPGe detector due to escape of photoelectrons and Compton‐scattered photons was studied for a point source with 59.5 keV energy. It was shown that both mechanisms, in addition to Ge x‐ray escape, leading to partial deposition of energy, could be observed in the same experiment. A Monte Carlo program was used to investigate these components of the response function. The results indicate that although the escape of scattered photons and Ge x‐rays are of the same magnitude, the escape of photoelectrons plays a more important role in the efficiency of a detector. Copyright © 2003 John Wiley & Sons, Ltd.