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Trace Analysis (trace + analysis)

Distribution by Scientific Domains

Medical Sciences	30%
Chemistry	30%

Selected Abstracts

Isotropic Component Trace Analysis

JOURNAL OF NEUROIMAGING, Issue 3 2005
Hitoshi Matsuzawa MD
ABSTRACT A new method for analyzing diffusion tensor imaging (DTI) of the brain, based on a recently introduced algorithm, lambda chart analysis (LCA), is presented. Pretreatment of a given DTI data set with LCA, which effectively segregates isotropic and aniso tropic components, allows for total removal of the anisotropic component from the DTI data set. The remaining pure isotropic component can therefore be subjected to further analysis simi lar to that applied in the trace histogram method. Deconvolution of the trace function yielded 3 Gaussian elements. Remapping of these 3 deconvoluted isotropic elements back onto the 2-dimensional image plane provided anatomical correlates of each element. The algorithm, referred to here as isotropic com ponent trace analysis, can be used as a pictorial analytic tool, as well as a numerical analytical tool, for the noninvasive assess ment of isotropic parenchymal components. The presented method provides quantitative indices of certain parenchymal parameters with better clarity than currently available methods. A ready-to-use program, EZ-LCA, for this powerful method is provided (available at http://coe.bri.niigata-u.ac.jp). [source]

Cover Picture: Electrophoresis 7'09

ELECTROPHORESIS, Issue 10 2009
Article first published online: 13 MAY 200
Issue no. 10 is a special issue on CE-MS edited by Phillipe Schmitt-Kopplin. It has three review articles describing recent advances in fundamental concepts, instrumentation, food safety, food quality, trace analysis of environmental pollutants and food contaminants, as well as many other applications. In addition, the special issue consists of 22 research articles on various topics of CE-MS, including technical and method developments, residue analysis in food and environmental applications and applications in diagnostic and life sciences. [source]

Affinity monolith preconcentrators for polymer microchip capillary electrophoresis

ELECTROPHORESIS, Issue 16 2008
Weichun Yang
Abstract Developments in biology are increasing demands for rapid, inexpensive, and sensitive biomolecular analysis. In this study, polymer microdevices with monolithic columns and electrophoretic channels were used for biological separations. Glycidyl methacrylate- co -ethylene dimethacrylate monolithic columns were formed within poly(methyl methacrylate) microchannels by in situ photopolymerization. Flow experiments in these columns demonstrated retention and then elution of amino acids under conditions optimized for sample preconcentration. To enhance analyte selectivity, antibodies were immobilized on monoliths, and subsequent lysozyme treatment blocked nonspecific adsorption. The enrichment capability and selectivity of these affinity monoliths were evaluated by purifying fluorescently tagged amino acids from a mixture containing green fluorescent protein (GFP). Twenty-fold enrichment and 91% recovery were achieved for the labeled amino acids, with a >25,000-fold reduction in GFP concentration, as indicated by microchip electrophoresis analysis. These devices should provide a simple, inexpensive, and effective platform for trace analysis in complex biological samples. [source]

Determination of trace cationic impurities in butylmethylimidazolium-based ionic liquids: From transient to comprehensive single-capillary counterflow isotachophoresis-zone electrophoresis

ELECTROPHORESIS, Issue 23 2006
Marek Urbánek
Abstract Determination of impurities in ionic liquids (ILs) remains a difficult task. In this work, the hyphenation of isotachophoretic,(ITP) preconcentration to zone electrophoresis,(ZE) has been explored for the trace analysis of the cationic impurities Na+, Li+, and methylimidazolium (MI+) in butylmethylimidazolium (BMI+)-based ILs. Simultaneous detection of UV-transparent and UV-absorbing impurities was ensured by a BGE composed of creatinine-acetate buffer. To induce ITP, three different strategies were evaluated: (i),Sample self-stacking ensured by the addition of ammonium acetate (NH4Ac) to 25,50-fold diluted IL solution (transient ITP). (ii),Complete ITP-ZE separation performed in a single capillary: ITP was realized in discontinuous electrolytes comprising an 80,mM NH4Ac, 40,mM acetic acid, 30,mM ,-CD, pH,5.05, leading electrolyte,(LE) and a 10,mM creatinine, 10,mM acetic acid, pH,4.9, terminating electrolyte,(TE). To create the ZE stage, the ITP stack of analytes was moved back toward the capillary inlet by pressure and simultaneously the capillary was filled with the BGE. This protocol made it possible to accommodate a 2.5-times diluted IL sample. (iii),Complete counterflow ITP-ZE with continuous electrokinetic sample supply: the ITP stage was performed in a capillary filled with a 150,mM NH4Ac, 75,mM acetic acid, 30,mM ,-CD, pH,5.0 LE, with 40-times diluted IL at the capillary inlet. BMI+ from IL acts as the terminating ion. The LODs reached in this latter case were at the 10 and 1,ppb levels for MI+ and Li+ in diluted IL matrix, respectively. [source]

Isotropic Component Trace Analysis

Assessment of an ECG event recorder in healthy dogs in a hospital environment

JOURNAL OF SMALL ANIMAL PRACTICE, Issue 4 2003
J. M. Eastwood
Ambulatory electrocardiography techniques are superior to standard electrocardiography in evaluating rhythm disturbances in dogs with episodic weakness or collapse. Disadvantages include cumbersome equipment, short recording periods and an inherent delay in trace analysis. A small programmable cardiac event recorder with combined automatic and owner-triggered recording capability was evaluated in 13 healthy dogs in a hospital environment. The unit was well tolerated and produced diagnostic recordings directly to a personal computer, with useful information about continuous heart rate. It detects premature complexes, pauses and bradycardias according to programmed detection thresholds. These events were counted frequently but trace review revealed concerns regarding specificity. Recordings were often triggered by sinus arrhythmia, sinus tachycardia and unclassifiable rate changes rather than by clinically significant arrhythmias. Correct detection of ventricular ectopic complexes, a single supraventricular premature complex, sinus arrest and second-degree atrioventricular block occurred in individual dogs. Visual review of all automatically recorded events was essential and significantly increased the time required for event recording analysis. Manual recordings might be more useful and the overall results suggest that further studies are warranted to evaluate the system in clinical cases in the home environment. [source]

Dissociation of the ,001, Dislocations and Their Interactions with Dislocation Loops in Tetragonal BaTiO3

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2006
Shun-Yu Cheng
Dislocations in pressureless-sintered BaTiO3 ceramics have been analyzed using transmission electron microscopy. Subjected to effective sintering stresses, dislocations were generated and multiplied in plastically deformed BaTiO3 crystals by the Frank,Read mechanism from both single- and double-ended sources. This is represented by dislocations encompassing a series of square-like borders that shared a common center. All border dislocations exhibited the characteristic scallop shape. True dislocation line directions (u) were determined by trace analysis and Burgers vectors (b) by contrast analysis for the dislocations dissociated from b=,001, into two half-partials following the type (I) reaction ofby climb on {001}. Dislocation interactions between the main dislocations created from plastic deformation and dislocation loops of b=,100, or ,110, forming condensation of intrinsic Schottky vacancies were also found to obey the type (IV) reaction of, the type (V) reactions of. Migrating dislocations and loops interacting mutually in several stages, illustrated schematically, before arriving at the configuration described by types (IV) and (V) were observed and discussed. [source]

The design of an on-line semi-preparative LC,SPE,NMR system for trace analysis,

MAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2005
Feng Xu
Abstract This paper reports the design of an on-line semi-preparative LC,SPE,NMR system and its use in the structural analysis of mixture components at the 0.02,1% level. The combination provides at least a five fold mass sensitivity increase over that obtained from typical analytical LC,SPE systems and a >30-fold total NMR sensitivity enhancement over analysis by LC,NMR. This is accomplished by using a novel on-line device to store, dilute (1,100-fold) and deliver (at an optimized flow-rate) the isolated component of interest to an SPE trap unit. The SPE unit consists of two cartridges connected in parallel to increase the overall SPE capacity and also to decrease the flow-rate through each trap for enhanced trapping efficiency. As the coupling of semi-preparative LC with NMR (through SPE) is well matched in terms of optimal mass loading for both techniques, only one LC,SPE cycle is required to enrich a 50 µg ml,1 component (1% in a 5 mg ml,1 mixture) for the acquisition of heteronuclear 1H,13C NMR data using a conventional NMR flow probe. Furthermore, analytes at the 0.02% level (,1 µg ml,1) can be studied using 2D 1H NMR techniques if peak cuts from replicate sample injections (,3) are accumulated into the storage/dilution unit and the resulting solution processed by just one SPE trap and elute cycle. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Determination of atrazine, deethylatrazine and simazine in water at parts-per-trillion levels using solid-phase extraction and gas chromatography/ion trap mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2003
W. T. Ma
Methods for trace analysis of atrazine and simazine in water have been developed by using stable-isotope dilution with detection by gas chromatography/mass spectrometry. D5 -Atrazine was used as the internal standard for the determination of atrazine and deethylatrazine, while 13C3 -simazine was used for simazine analysis. Water samples were fortified with known amounts of the internal standards and submitted to solid-phase extraction with a C18 bonded-silica cartridge. A gas chromatograph coupled with an ion-trap mass spectrometer was used to analyze the water sample extracts. Method detection limits were 38 parts-per-trillion (ppt) for atrazine and deethylatrazine and 75 ppt for simazine. The accuracy of the method, represented by relative analytical errors, was less than 15%, and the method precision was less than 5% (relative standard deviation, n,=,9). The method was successfully applied to analyze surface water samples collected from a reservoir and a river at ppt levels. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Determination of non-steroidal estrogens in breast milk, plasma, urine and hair by gas chromatography/mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2002
Man Ho Choi
It is suspected that all the natural estrogens occurring in the human body, as well as dietary and synthetic estrogens, diversely affect the endocrine system depending on their exposure patterns. More rapid, reliable and accurate measurements of these compounds in various biological matrices are thus becoming an important task. After solid-phase extraction using an Oasis HLB extraction cartridge, the estrogen concentrates were derivatized with a mixture of N -methyl- N -trifluorotrimethylsilylacetamide/ammonium iodide/dithioerythritol (1000:4:5, v/w/w) for analysis by gas chromatography/mass spectrometry in the selected ion-monitoring (SIM) mode. The qualitative identification of estrogens detected in SIM mode was further confirmed by tandem mass spectrometry using low-energy collision-induced dissociation (CID) mode. The method for the assay of the 20 estrogens was linear over the ranges of 1,1000,µg/L for biological fluids and 1,200,µg/kg for hair with high correlation coefficient (>0.99). The limits of quantitation (LOQ) ranged from 1.0,10,µg/L (or,µg/kg) and the limit of detection ranged from 0.2,3,µg/L (or,µg/kg). The average precision (% CV) and accuracy (% bias) of the method determined at the LOQ, low, and medium concentrations were in the ranges 2.6,9.2 and ,4.1,7.7, respectively. The average extraction recovery of the estrogens from plasma and hair at the three concentration levels varied in the ranges 77,103% (1.9,14.3% CV) and 73,104% (3.1,14%), respectively. The distribution patterns of the estrogens were characteristic of each biosample. Five estrogens in the range 1.5,44.9,µg/L were measured in breast milk, 8 estrogens in the range 3.5,322,µg/L in plasma, 12 estrogens at 1.2,442,µg/L in urine, and biochanin-A at 13.2,39.1,µg/kg in hair. Because of its high sensitivity, good precision and specificity, the present method was found suitable for the trace analysis of dietary and synthetic estrogens in complex biosamples such as breast milk, plasma, urine and hair. Copyright © 2002 John Wiley & Sons, Ltd. [source]