@article {2674, title = {Competitive Adsorption of Toluene and n-Alkanes at Binary Solution/Silica Interfaces}, journal = {Journal of Physical Chemistry C}, volume = {113}, number = {47}, year = {2009}, note = {ISI Document Delivery No.: 520FMTimes Cited: 2Cited Reference Count: 48Yang, Zheng Li, Qifeng Hua, Rui Gray, Murray R. Chou, Keng C.}, month = {Nov}, pages = {20355-20359}, type = {Article}, abstract = {The competitive adsorption of toluene and n-alkanes at binary solution/silica interfaces was studied at room temperature using IR-visible sum frequency generation vibrational spectroscopy. The Surface coverage of toluene for toluene-pentane, toluene-heptane, and toluene-tetradecane mixtures was measured over the complete mole fraction range from 0 to 1. The competitive adsorption process was reversible, and the toluene coverage only depended oil the bulk mole fraction, not on the history of the system. The estimated molar adsorption free energy of toluene is 3.4 +/- 0.3, 1.8 +/- 0.3, and 0.84 +/- 0.3 kJ/mol higher than pentane, heptane, and tetradecane, respectively. Overall, toluene competes favorably on silica, and the molar adsorption free energy of alkanes increases as the chain length increases. It is consistent with the observed SFG spectra, indicating that the alkanes lie flat on the silica surface.}, keywords = {ACCELERATED SOLVENT-EXTRACTION, bitumen, CONFORMATION, FREQUENCY VIBRATIONAL SPECTROSCOPY, H STRETCHING MODES, LIQUID-CHROMATOGRAPHY, NORMAL-ALKYL CHAINS, ORIENTATION, SUM-FREQUENCY, SURFACE}, isbn = {1932-7447}, url = {://000271826100033}, author = {Yang, Z. and Li, Q. F. and Hua, R. and Gray, M. R. and Chou, K. C.} } @article {2343, title = {Fruit-Surface Flavonoid Accumulation in Tomato Is Controlled by a SIMYB12-Regulated Transcriptional Network}, journal = {Plos Genetics}, volume = {5}, number = {12}, year = {2009}, note = {ISI Document Delivery No.: 542CTTimes Cited: 3Cited Reference Count: 58Adato, Avital Mandel, Tali Mintz-Oron, Shira Venger, Ilya Levy, Dorit Yativ, Merav Dominguez, Eva Wang, Zhonghua De Vos, Ric C. H. Jetter, Reinhard Schreiber, Lukas Heredia, Antonio Rogachev, Ilana Aharoni, Asaph}, month = {Dec}, pages = {23}, type = {Article}, abstract = {The cuticle covering plants{\textquoteright} aerial surfaces is a unique structure that plays a key role in organ development and protection against diverse stress conditions. A detailed analysis of the tomato colorless-peel y mutant was carried out in the framework of studying the outer surface of reproductive organs. The y mutant peel lacks the yellow flavonoid pigment naringenin chalcone, which has been suggested to influence the characteristics and function of the cuticular layer. Large-scale metabolic and transcript profiling revealed broad effects on both primary and secondary metabolism, related mostly to the biosynthesis of phenylpropanoids, particularly flavonoids. These were not restricted to the fruit or to a specific stage of its development and indicated that the y mutant phenotype is due to a mutation in a regulatory gene. Indeed, expression analyses specified three R2R3-MYB-type transcription factors that were significantly down-regulated in the y mutant fruit peel. One of these, SIMYB12, was mapped to the genomic region on tomato chromosome 1 previously shown to harbor the y mutation. Identification of an additional mutant allele that co-segregates with the colorless-peel trait, specific down-regulation of SlMYB12 and rescue of the y phenotype by overexpression of SlMYB12 on the mutant background, confirmed that a lesion in this regulator underlies the y phenotype. Hence, this work provides novel insight to the study of fleshy fruit cuticular structure and paves the way for the elucidation of the regulatory network that controls flavonoid accumulation in tomato fruit cuticle.}, keywords = {AFFECTS VEGETATIVE DEVELOPMENT, ARABIDOPSIS-THALIANA, EVOLUTION, EXPRESSION, GENE, IDENTIFICATION, LIQUID-CHROMATOGRAPHY, METABOLISM, PHENYLPROPANOID BIOSYNTHESIS, REGULATOR}, isbn = {1553-7390}, url = {://000273469700027}, author = {Adato, A. and Mandel, T. and Mintz-Oron, S. and Venger, I. and Levy, D. and Yativ, M. and Dominguez, E. and Wang, Z. H. and De Vos, R. C. H. and Jetter, R. and Schreiber, L. and Heredia, A. and Rogachev, I. and Aharoni, A.} } @article {2231, title = {State-of-the-art in atmospheric pressure photoionization for LC/MS}, journal = {Analytica Chimica Acta}, volume = {627}, number = {1}, year = {2008}, note = {ISI Document Delivery No.: 358IYTimes Cited: 23Cited Reference Count: 147Robb, Damon B. Blades, Michael W.Sp. Iss. SI}, month = {Oct}, pages = {34-49}, type = {Review}, abstract = {This review presents our perspective on the state-of-the-art of atmospheric pressure photoionization (APPI) for LC/MS. Its focus is on APPI{\textquoteright}s capabilities and how to utilize them fully. The introduction includes a brief recounting of the history of APPI{\textquoteright}s development, as well as a summary of its operating principles and current position in the field. The primary ionization mechanisms in APPI are then addressed, including direct analyte photoionization (PI), dopant/solvent PI, and thermospray. Next a summary of the ion-molecule reaction pathways available for analyte ionization is presented, along with the conditions required for activating them. APPI{\textquoteright}s performance characteristics are then examined. in effect, this review is an interim report on progress made since Rafaelli and Saba concluded that "The ability... to direct the preferential ion formation towards one particular type...can be extremely useful for qualitative and quantitative determinations. For this purpose, a better insight in the processes involved in the ionization step is strongly needed" [A. Raffaelli, A. Saba, Mass Spectrom. Rev. 22 (2003) 318]. In the conclusion, we focus on areas of APPI technology identified as being either unoptimized or largely unexplored, and having the potential to be improved upon-the crux being that with further research and development improvements in the performance, capabilities, and ease-of-use of APPI may reasonably be anticipated. (C) 2008 Elsevier B.V. All rights reserved.}, keywords = {ACTIVATED CHEMICAL-IONIZATION, AROMATIC-HYDROCARBONS, atmospheric pressure, BROMINATED FLAME RETARDANTS, CARBON, ELECTROSPRAY-IONIZATION, HUMAN PLASMA, LC-MS/MS, liquid chromatography/mass, LIQUID-CHROMATOGRAPHY, PHOTOIONIZATION, POLYCYCLIC, POROUS GRAPHITIC, PROTON-TRANSFER, review, SPECTROMETRY, TANDEM-MASS-SPECTROMETRY}, isbn = {0003-2670}, url = {://000259911600004}, author = {Robb, D. B. and Blades, M. W.} } @article {1491, title = {Analysis of amphetamine, methamphetamine and methylenedioxy-methamphetamine by micellar capillary electrophoresis using cation-selective exhaustive injection}, journal = {Electrophoresis}, volume = {27}, number = {16}, year = {2006}, note = {ISI Document Delivery No.: 081RBTimes Cited: 18Cited Reference Count: 40Meng, Pinjia Fang, Ning Wang, Meng Liu, Huwei Chen, David D. Y.}, month = {Aug}, pages = {3210-3217}, type = {Article}, abstract = {Cation-selective exhaustive injection (CSEI) is used as an on-line concentration method for the high-sensitivity analysis of illicit amphetamines using CE. Optimum conditions for the determination of amphetamine, methamphetamine and methylenedioxy-methamphetamine were investigated. Sodium dodecyl sulfate (25 mM) in 100 mM phosphate buffer (pH 2.9) with 20\% methanol as organic additive was used as the background electrolyte for CE separation. The LOD, based on an S/N of 3:1, was about 0.01 mu g/mL using normal capillary micellar electrokinetic chromatography, while by using CSEI in combination with micellar sweeping the sensitivity increased up to 1000-fold with the LOD lower than 50 pg/mL. The reproducibility of CSEI combined with micellar sweeping for analyzing amphetamines was satisfactory (relative standard deviation around 10\% by using area ratios against an internal standard). This method is highly sensitive and can be used to analyze trace amount amphetamines in human hair.}, keywords = {amphetamine, AMPLIFIED SAMPLE STACKING, analysis, cation-selective exhaustive injection, CHROMATOGRAPHY, CHROMATOGRAPHY-MASS SPECTROMETRY, ELECTROKINETIC, FLUORESCENCE DETECTION, illicit drug, LIQUID-CHROMATOGRAPHY, methamphetamine, methylenedioxy-methamphetamine, NEUTRAL ANALYTES, ONLINE CONCENTRATION, REVERSE MIGRATING MICELLES, SOLID-PHASE MICROEXTRACTION, ZONE-ELECTROPHORESIS}, isbn = {0173-0835}, url = {://000240333600007}, author = {Meng, P. J. and Fang, N. and Wang, M. and Liu, H. W. and Chen, D. D. Y.} } @article {1529, title = {Factors affecting primary ionization in dopant-assisted atmospheric pressure photoionization (DA-APPI) for LC/MS}, journal = {Journal of the American Society for Mass Spectrometry}, volume = {17}, number = {2}, year = {2006}, note = {ISI Document Delivery No.: 012ZFTimes Cited: 25Cited Reference Count: 20}, month = {Feb}, pages = {130-138}, type = {Article}, abstract = {The sensitivity of dopant-assisted atmospheric pressure photoionization (DA-APPI) for LC/MS is generally reduced at higher solvent flow rates. Theory suggests that quenching of excited-state precursors to the dopant ions, via collisions with vaporized solvent molecules, may be one mechanism responsible for this trend. To ascertain if the primary rate of ionization is affected by quenching, experiments were performed utilizing an ionization detector to determine the primary ion current generated by irradiating vaporized mixtures of toluene dopant and methanol solvent. The results indicate that no loss of primary ion current occurs as the solvent flow is increased, provided the dopant-to-solvent ratio is held constant. Additional primary ion current can always be generated by increasing the dopant flow rate and/or the lamp power. Thus, quenching of excited-state precursors to the dopant ions, leading to a reduction in the primary rate of ionization, is not the mechanism responsible for the observed loss of sensitivity at higher liquid solvent flow rates.}, keywords = {DETECTOR, LIQUID-CHROMATOGRAPHY, MASS-SPECTROMETRY, PERFORMANCE, PLASMA, SOLVENT FLOW}, isbn = {1044-0305}, url = {://000235378700003}, author = {Robb, D. B. and Blades, M. W.} } @article {1221, title = {Arsenic compounds in the haemolymph of the Dungeness crab, Cancer magister, as determined by using HPLC on-line with inductively coupled plasma mass spectrometry}, journal = {Journal of Environmental Monitoring}, volume = {7}, number = {2}, year = {2005}, note = {ISI Document Delivery No.: 901JTTimes Cited: 3Cited Reference Count: 29}, month = {Feb}, pages = {122-126}, type = {Article}, abstract = {Arsenobetaine, two arsenosugars, dimethylarsinate and several unidentified arsenic species were detected in extracts of the haemolymph of the Dungeness crab, Cancer magister, by using HPLC-ICP-MS. This is the first report of the presence of arsenosugars in the haemolymph/blood of marine animals. Total, extractable and residual arsenic concentrations were determined by ICP-MS. The concentration of total arsenic was in the range of 1.4-3.8 mug ml(-1). Nearly all (98\%) the arsenic was found to be extractable, and accounted for primarily by arsenobetaine, two arsenosugars and dimethylarsinate. The results demonstrate that arsenic compounds present in the diet of crabs are not fully metabolized in the gut. They are, at least partly, taken up into the haemolymph. The concurrence of arsenobetaine and arsenosugars suggests that the use of repeated haemolymph sampling in crustaceans could facilitate investigations into the kinetics of the biotransformation pathways of arsenic compounds. Finally, the present study clearly demonstrates the unique capabilities of HPLC-ICP-MS for the detection and identification of minor arsenic components amongst the predominant arsenobetaine.}, keywords = {ANAEROBIC DECOMPOSITION, arsenobetaine, CADMIUM ACCUMULATION, CARCINUS-MAENAS, LIQUID-CHROMATOGRAPHY, MARINE-ENVIRONMENT, PHYSIOLOGICAL CONDITION, SARGASSUM-LACERIFOLIUM, SHRIMP CRANGON-CRANGON, SPECIATION}, isbn = {1464-0325}, url = {://000227279500011}, author = {Norum, U. and Lai, V. W. M. and Pergantis, S. A. and Cullen, W. R.} } @article {1237, title = {Effects of solvent flow, dopant flow, and lamp current on dopant-assisted atmospheric pressure photoionization (DA-APPI) for LC-MS. Ionization via proton transfer}, journal = {Journal of the American Society for Mass Spectrometry}, volume = {16}, number = {8}, year = {2005}, note = {ISI Document Delivery No.: 952BFTimes Cited: 42Cited Reference Count: 37}, month = {Aug}, pages = {1275-1290}, type = {Article}, abstract = {In this paper, the effects of solvent flow, dopant flow, and lamp power on proton transfer ionization in dopant-assisted (DA) atmospheric pressure photoionization (APPI) are investigated. A broad theoretical framework is presented, describing the primary photoionization process, the formation of protonated-solvent cluster ions, and the balance between analyte ion creation via proton transfer and loss via recombination. The principal experimental test system utilized methanol as the solvent, toluene as the dopant, and acridine as the analyte. Comparisons are made between acridine and a less basic compound, 9-methylanthracene (9-MA). Experimental determinations of the trends in the analyte MH+ signal and the total ion current (TIC) with variations in the subject parameters are provided. Experimental results and theory demonstrate that both the analyte signal and the TIC approach asymptotic limits with increases in dopant flow and/or lamp current (two factors which dictate the rate of photoion generation). The data show that these limits are lowered at higher solvent flow rates. These results are attributed to the recombination loss process, the rate of which increases with the second power of ion concentration. We deduce that the recombination rate constant increases with solvent flow rate, a consequence of the growth of ion-solvent clusters. Cluster growth is also believed to be a factor in the dramatic loss of sensitivity for 9-MA that occurs as the solvent flow is raised, because larger protonated-solvent cluster ions have greater solvation energies and may be unreactive with compounds having low gas-phase basicity and/or low solvation energy.}, keywords = {DETECTOR, GAS-PHASE, ION-SOURCE, LIQUID-CHROMATOGRAPHY, MASS-SPECTROMETRY, METHANOL, PLASMA, SENSITIVITY, SOLVATION, SYSTEM}, isbn = {1044-0305}, url = {://000230975700009}, author = {Robb, D. B. and Blades, M. W.} } @article {1225, title = {Entropic interaction chromatography: Separating proteins on the basis of size using end-grafted polymer brushes}, journal = {Biotechnology and Bioengineering}, volume = {90}, number = {1}, year = {2005}, note = {ISI Document Delivery No.: 909ETTimes Cited: 9Cited Reference Count: 48}, month = {Apr}, pages = {1-13}, type = {Article}, abstract = {Partitioning of a macromolecule into the interfacial volume occupied by a grafted polymer brush decreases the configurational entropy (Delta S(c)brush) of the terminally attached linear polymer chains due to a loss of free volume. Self-consistent field theory (SCF) calculations are used to show that Delta S(c)brush is a strong function of both the size (MW,) of the partitioning macromolecule and the depth of penetration into the brush volume. We further demonstrate that the strong dependence of Delta S(c)brush on MW, provides a novel and powerful platform, which we call entropic interaction chromatography (EIC), for efficiently separating mixtures of proteins on the basis of size. Two EIC columns, differing primarily in polymer grafting density, were prepared by growing a brush of poly(methoxyethyl acrylamide) chains on the surface of a widepore (1,000-angstrom pores, 64-mu m diameter rigid beads) resin (Toyopearl AF-650M) bearing surface aldehyde groups. Semipreparative 0.1-L columns packed with either EIC resin provide reduced-plate heights of 2 or less for efficient separation of globular protein mixtures over at least three molecular-weight decades. Protein partitioning within these wide-pore EIC columns is shown to be effectively modeled as a thermodynamically controlled process, allowing partition coefficients (K-p) and elution chromatograms to be accurately predicted using a column model that combines SCF calculation of Kp values with an equilibrium-dispersion type model of solute transport through the column. This model is used to explore the dependence of column separation efficiency on brush properties, predicting that optimal separation of proteins over a broad MW, range is achieved at low to moderate grafting densities and intermediate chain lengths. (c) 2005 Wiley Periodicals, Inc.}, keywords = {ADSORPTION, CHAIN MOLECULES, CONSISTENT-FIELD THEORY, entropic interaction chromatography, equilibrium dispersion, EXCLUSION CHROMATOGRAPHY, GEL FILTRATION, grafted polymer brush, HUMAN SERUM-ALBUMIN, LIQUID-CHROMATOGRAPHY, MODEL, MOLECULAR-WEIGHT, MONTE-CARLO, protein purification, size exclusion chromatography, STATISTICAL-THEORY}, isbn = {0006-3592}, url = {://000227843800001}, author = {Pang, P. and Koska, J. and Coad, B. R. and Brooks, D. E. and Haynes, C. A.} } @article {918, title = {Arsenic speciation in human urine: are we all the same?}, journal = {Toxicology and Applied Pharmacology}, volume = {198}, number = {3}, year = {2004}, note = {ISI Document Delivery No.: 844GRTimes Cited: 26Cited Reference Count: 34}, month = {Aug}, pages = {297-306}, type = {Review}, abstract = {we studied the arsenic speciation in human urine samples by using high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). We investigated the arsenic speciation in the urine collected from nine volunteers during a 3-day period after a meal of blue mussels, Mytilus edulis. We also studied the effect of cooking on the arsenic speciation. Arsenobetaine and dimethylarsinic acid (DMAA) were the major arsenic metabolites found in the urine samples. Significant amounts of unknown metabolites were also detected. The excretion patterns of arsenic from individuals were generally similar except for two subjects. One of whom excreted high amounts of arsenobetaine even though no arsenic-rich food was eaten for 3 days before the experiment. The results reveal that we need a better understanding of the metabolism of arsenic compounds by human. (C) 2004 Elsevier Inc. All rights reserved.}, keywords = {arsenic, arsenobetaine, arsenosugar, ENVIRONMENT, HPLC, ICP-MS, IDENTIFICATION, INGESTION, LIQUID-CHROMATOGRAPHY, MASS-SPECTROMETRY, METABOLITES, METHYLATED ARSENICALS, mussel, PRODUCTS, TRIVALENT, urine}, isbn = {0041-008X}, url = {://000223146600007}, author = {Lai, V. W. M. and Sun, Y. M. and Ting, E. and Cullen, W. R. and Reimer, K. J.} } @article {959, title = {Efficient synthesis of isotopically pure isotope-coded affinity tagging reagents}, journal = {Bioconjugate Chemistry}, volume = {15}, number = {1}, year = {2004}, note = {ISI Document Delivery No.: 766UDTimes Cited: 7Cited Reference Count: 24}, month = {Jan-Feb}, pages = {224-230}, type = {Article}, abstract = {Synthesis of an isotopically pure d(8)-ICAT linker, N- [(5,5,6,6,8,8 9,9-H-2)-13-biotinamido-4,7,10-trioxatridecanyl] tert-butyloxy carbamide (12), has been achieved in seven steps with an overall yield of 33\%. Conjugation of exchange-inert d(4)-starting materials by classic etherification reaction yielded a pure synthon, carrying eight deuteriums that remained exchange-inert throughout subsequent reactions. This modified synthesis constitutes a significant improvement to the reported syntheses of "heavy" ICAT reagent in terms of expense, yield, and isotopic retention. This synthesis is easily adapted to incorporate additional deuterium atoms and is equally applicable for incorporation of either C-13 and/or O-18. In addition, this synthesis allows for the introduction of different orthogonal functionalities and provides for a high yielding series of differentially encoded ICAT tags.}, keywords = {GEL-ELECTROPHORESIS, IONIZATION MASS-SPECTROMETRY, LIQUID-CHROMATOGRAPHY, PEPTIDES, PROTEINS, PROTEOME ANALYSIS, TAGS}, isbn = {1043-1802}, url = {://000188393200027}, author = {Patel, A. and Perrin,David M.} } @article {427, title = {Arsenic speciation in whelks, Bucciunum undatum}, journal = {Applied Organometallic Chemistry}, volume = {16}, number = {8}, year = {2002}, note = {ISI Document Delivery No.: 582FYTimes Cited: 6Cited Reference Count: 2510th International Symposium on Natural and Industrial Arsenic of the Japanese-Arsenic-Scientists-SocietyNOV 29-30, 2001TOKYO, JAPANJapanese Arsen Scientists Soc}, month = {Aug}, pages = {458-462}, type = {Proceedings Paper}, abstract = {The arsenic species present in the foot muscle of whelks, Buccinum undatum, collected from Newfoundland, Canada, were characterized by using high-performance liquid chromatography-inductively coupled plasma mass spectrometry. All samples contain high amounts of arsenic, mostly over 100 mug g(-1) (as arsenic, dry weight basis), and one sample contained up to 1360 mug g(-1). These values are considerably higher than those reported in other gastropods. Speciation studies of representative samples revealed arsenobetaine as the major water-soluble arsenic compound, together with trace amounts of an arsenosugar. No inorganic arsenic species were detected in the sample extracts, indicating that consumption of the whelks poses little human risk. Copyright (C) 2002 John Wiley Sons, Ltd.}, keywords = {arsenic, arsenobetaine, arsenosugar, HPLC, ICP-MS, LIQUID-CHROMATOGRAPHY, MASS SPECTROMETRY, SPECIATION, whelks}, isbn = {0268-2605}, url = {://000177340200011}, author = {Lai, V. W. M. and Beach, A. S. and Cullen, W. R. and Ray, S. and Reimer, K. J.} } @article {5083, title = {Unstable trivalent arsenic metabolites, monomethylarsonous acid and dimethylarsinous acid}, journal = {Journal of Analytical Atomic Spectrometry}, volume = {16}, number = {12}, year = {2001}, note = {ISI Document Delivery No.: 498MYTimes Cited: 95Cited Reference Count: 52}, pages = {1409-1413}, type = {Article}, abstract = {Two key arsenic metabolites, monomethylarsonous acid (MMA(III)) and dimethylarsinous acid (DMA(III)), have recently been detected in human urine. There is an increasing interest in the speciation of these metabolites in humans because of their demonstrated effects on cellular toxicity and DNA damage. However, there is no information on the oxidative stability of these arsenic species. It is not known whether and to what extent these trivalent metabolites are changed during sample handling and storage. The objective of this study was to demonstrate the oxidative conversion of these arsenic species during sample storage. We compared the effects of the storage temperature (25, 4, and -20 degreesC) and storage duration (up to 5 months) on the stability of MMA(III) and DMA(III) in de-ionized water and in human urine. We used HPLC with hydride generation atomic fluorescence detection for the speciation of arsenic. This method provided sub-mug L-1 to low-mug L-1 detection limits for each arsenic species. We found that the oxidation of MMA(III) and DMA(III) was matrix and temperature dependent. Low temperature conditions (4 and -20 degreesC) improved the stability of these arsenic species over the room temperature storage condition. MMA(III) in de-ionized water was relatively stable for almost 4 months, when stored at 4 or -20 degreesC with less than 10\% of MMA(III) oxidized to MMA(V). In contrast, most of MMA(III) ( 90\%) in urine was oxidized to MMA(V) over the 5 month period under the 4 or -20 degreesC storage condition. At 25 degreesC, MMA(III) in urine was completely oxidized to MMA(V) within a week. DMA(III) in deionized water was stable for only 2-3 days, being rapidly oxidized to DMA(V). DMA(III) in urine was completely oxidized to DMA(V) within a day at 4 or -20 degreesC. The conversion of DMA(III) to DMA(V) in urine at 25 degreesC was complete in 17 h. These results show that MMA(III) and DMA(III) are much less stable than other arsenic species, and their stability depends on sample matrix and temperature.}, keywords = {ATOMIC FLUORESCENCE DETECTION, BLACKFOOT DISEASE, chemical, DRINKING-WATER, ENZYMATIC, GLUTATHIONE-REDUCTASE, HUMAN HEPATOCYTES, HUMAN URINE, LIQUID-CHROMATOGRAPHY, METHYLATION, RABBIT LIVER, SPECIATION}, isbn = {0267-9477}, url = {://000172516100011}, author = {Gong, Z. L. and Lu, X. F. and Cullen, W. R. and Le, X. C.} } @article {4924, title = {Collision-induced dissociation of ions within the orifice-skimmer region of an electrospray mass spectrometer}, journal = {Analytical Chemistry}, volume = {72}, number = {4}, year = {2000}, note = {ISI Document Delivery No.: 285HETimes Cited: 38Cited Reference Count: 33}, month = {Feb}, pages = {791-799}, type = {Article}, abstract = {An equation was derived to describe the variation of the gas number density within the region between the orifice and the skimmer of an electrospray ionization mass spectrometer. The equation was used to develop a semiquantitative model to predict the value of orifice voltages that lead to ion fragmentation within this region. This model made it possible to predict the types of solvent adducts observed for analytes at various orifice voltages. In addition, it is shown that a small number of high-energy collisions is equally effective for collision-induced dissociation as compared to a large number of low-energy collisions. Finally, this model is tested with different background electrolyte solutions and a different electrospray mass spectrometer. It is demonstrated that controlled fragmentation studies can be performed on single-quadrupole mass spectrometers, and the proposed model gives a reasonable description of the fragmentation process in both spectrometers.}, keywords = {capillary electrophoresis, CYTOCHROME-C, DYNAMICS, IDENTIFICATION, INTERFACE, IONIZATION, LIQUID-CHROMATOGRAPHY, PROTEINS, SENSITIVITY, SEPARATION}, isbn = {0003-2700}, url = {://000085383000019}, author = {Schneider, B. B. and Chen, D. D. Y.} } @article {4206, title = {The effect of complexation additives on analyte migration behavior in capillary electrochromatography}, journal = {Electrophoresis}, volume = {19}, number = {8-9}, year = {1998}, note = {ISI Document Delivery No.: ZY715Times Cited: 6Cited Reference Count: 22}, month = {Jun}, pages = {1452-1460}, type = {Article}, abstract = {In capillary electrochromatography (CEC), analytes often have different mobilities in the mobile phase, and often are involved in multiple equilibria. In this paper, the migration behavior of an analyte in CEC is described by a general equation in which individual capacity factors are used to describe the tendency of the analyte to exist as the various analyte species present in a separation system, and the effects of both field and equilibrium are accounted for. The resolution of two analytes is shown to be related linearly to the ratio of their migration rates. The effect of the electroosmotic flow (EOF) in CEC is more complicated than in CE because it is experienced only by a fraction of the analyte, whereas in CE, it is experienced by all analyte species. A procedure for calculating the electrophoretic mobility of the analyte based on the fraction of the analyte in the buffer is demonstrated. The effect of the EOF on resolution is also discussed.}, keywords = {additives, capillary electrochromatography, COMPLEXATION, ELECTROPHORESIS, LIQUID-CHROMATOGRAPHY, multiple equilibria, PARAMETERS, separation theory, SEPARATIONS}, isbn = {0173-0835}, url = {://000074652100040}, author = {Bowser, M. T. and Chen, D. D. Y.} } @article {4204, title = {Recent developments towards a unified theory for separation science}, journal = {Electrophoresis}, volume = {19}, number = {10}, year = {1998}, note = {ISI Document Delivery No.: 108XDTimes Cited: 0Cited Reference Count: 30}, month = {Jul}, pages = {1586-1589}, type = {Review}, abstract = {Various techniques for chemical separation can be described using a generally applicable theory. There are several schools of thought on how a unified separation science should be developed. The theories described include the mass balance equation (i.e. moving boundary), virtual migration distances, and the use of individual capacity factors.}, keywords = {CAPILLARIES, HIGH-PERFORMANCE ELECTROPHORESIS, individual capacity factors, INTERPLAY, LIQUID-CHROMATOGRAPHY, mass balance equation, resolution equation, separation science, virtual migration distances}, isbn = {0173-0835}, url = {://000075290300010}, author = {Bowser, M. T. and Chen, D. D. Y.} } @article {3908, title = {Redefining the separation factor: A potential pathway to a unified separation science}, journal = {Electrophoresis}, volume = {18}, number = {15}, year = {1997}, note = {ISI Document Delivery No.: YW557Times Cited: 20Cited Reference Count: 38}, month = {Dec}, pages = {2928-2934}, type = {Article}, abstract = {Understanding the separation process in capillary electrophoresis (CE leads to the unification of the theories for separation science; While the separation of analytes is governed by equilibria in chromatography, and by (centrifugal) field in ultracentrifugation, the separation in CE is governed by both equilibria and (electric) field. Therefore, a comprehensive separation theory that describes the separation process of analytes in CE should be able to describe the separation processes in both chromatography and ultracentrifugation. In this paper, we propose that individual capacity factors for each analyte species be used to describe the migration behavior of an analyte. The effect of field on each analyte species, as well as the effect of equilibria are considered in deriving a generalized equation that is applicable for all separation techniques. The separation factor defined at present does not directly relate to the migration rates of the analytes, and therefore can not be used in a generalized theory. We propose that the ratio of the migration rates of a pair of analytes (gamma) should be used as the separation factor, instead of the ratio of the two capacity factors. When gamma is used to describe the separation of two closely migrating analytes, all separation techniques have the same resolution equation.}, keywords = {BETA-CYCLODEXTRIN, capacity factor, capillary electrophoresis, CHROMATOGRAPHY, ELECTROKINETIC CHROMATOGRAPHY, ELECTROPHORETIC CHIRAL SEPARATIONS, ENANTIOMERS, LIQUID-CHROMATOGRAPHY, PARAMETERS, RESOLUTION, SELECTIVITY, separation factor, TIOCONAZOLE, ULTRACENTRIFUGATION, ZONE ELECTROPHORESIS}, isbn = {0173-0835}, url = {://000071948300033}, author = {Bowser, M. T. and Bebault, G. M. and Peng, X. J. and Chen, D. D. Y.} } @article {2852, title = {DETERMINATION OF URINARY ARSENIC AND IMPACT OF DIETARY ARSENIC INTAKE}, journal = {Talanta}, volume = {40}, number = {2}, year = {1993}, note = {ISI Document Delivery No.: KU309Times Cited: 47Cited Reference Count: 40}, month = {Feb}, pages = {185-193}, type = {Article}, abstract = {An analytical method based on microwave decomposition and flow injection analysis (FIA) coupled to hydride generation atomic absorption spectrometry (HGAAS) is described. This is used to differentiate arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) from organoarsenic compounds usually present in seafood. Without microwave digestion, direct analysis of urine by HGAAS gives the total concentration of As(III), As(V), MMA and DMA because organoarsenic compounds such as arsenobetaine, usually found in most seafood, are not reducible upon treatment with borohydride and therefore cannot be determined by using the hydride generation technique. The microwave oven digestion procedure with potassium persulfate and sodium hydroxide as decomposition reagents completely decomposes all arsenicals to arsenate and this can be measured by HGAAS. Microwave decomposition parameters were studied to achieve efficient decomposition and quantitative recovery of arsenobetaine spiked into urine samples. The method is applied to the determination of urinary arsenic and is useful for the assessment of occupational exposure to arsenic without intereference from excess organoarsenicals due to the consumption of seafood. Analysis of urine samples collected from an individual who ingested some seafood revealed that organoarsenicals were rapidly excreted in urine. After the ingestion of a 500-g crab, a 10-fold increase of total urinary arsenic was observed, due to the excretion of organoarsenicals. The maximum arsenic concentration was found in the urine samples collected approximately between 4 to 17 hr after eating seafood. However, the ingestion of organoarsenic-containing seafoods such as crab, shrimp and salmon showed no effect on the urinary excretion of inorganic arsenic, MMA and DMA.}, keywords = {arsenobetaine, ATOMIC-ABSORPTION SPECTROMETRY, EMISSION-SPECTROMETRY, EXCRETION, HYDRIDE GENERATION, INGESTION, LIQUID-CHROMATOGRAPHY, METABOLISM, REDUCTION, SPECIATION}, isbn = {0039-9140}, url = {://A1993KU30900013}, author = {Le, X. C. and Cullen, W. R. and Reimer, K. J.} } @article {7295, title = {DECOMPOSITION OF ORGANOARSENIC COMPOUNDS BY USING A MICROWAVE-OVEN AND SUBSEQUENT DETERMINATION BY FLOW-INJECTION HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROMETRY}, journal = {Applied Organometallic Chemistry}, volume = {6}, number = {2}, year = {1992}, note = {ISI Document Delivery No.: HQ168Times Cited: 61Cited Reference Count: 33INTERNATIONAL CONF ON ENVIRONMENTAL AND BIOLOGICAL ASPECTS OF MAIN-GROUP ORGANOMETALS ( ICEBAMO )SEP 15-19, 1991PADUA, ITALYUNIV PADUA, ITALIAN CHEM SOC}, month = {Apr}, pages = {161-171}, type = {Proceedings Paper}, abstract = {Environmentally important organoarsenicals such as arsenobetaine, arsenocholine and tetramethylarsonium ion do not form volatile hydrides under the commonly used analytical conditions on treatment with borohydride and it has been difficult to determine their concentrations without further derivatization. This paper describes a rapid method which completely decomposes and oxidizes these arsenicals to arsenate by using potassium persulphate and sodium hydroxide with the aid of microwave energy. The quantitative decomposition of these species permits their determination at low nanogram levels, by hydride generation atomic absorption spectrometry (HG AA). A new hydride generator which has high efficiency and minimum dead volume and therefore is suitable for flow injection analysis (FIA) is also described. A system combining flow injection analysis, on-line microwave oven digestion, and hydride generation followed by atomic absorption measurement, is developed. This system is capable of performing analysis at a sample throughput of 100-120 per hour. Calibration curves were linear from 10 to 200 ng cm-3 of arsenic and the detection limit was 5 ng cm-3 for a 100-mu-l injection or 0.5 ng of arsenic. All ten organoarsenic compounds studied gave arsenate as the decomposition product, which was confirmed by using molybdenum blue photometric measurement.}, keywords = {ABSORPTION SPECTROMETRY, arsenic, arsenobetaine, atomic, DECOMPOSITION, DETERMINATION, DISSOLUTION, ENVIRONMENT, FLOW INJECTION ANALYSIS, HYDRIDE GENERATION, IDENTIFICATION, LIQUID-CHROMATOGRAPHY, MICROWAVE OVEN DIGESTION, MUSCLE REFERENCE MATERIAL, QUANTITATION, TRACE-ELEMENTS, WATER}, isbn = {0268-2605}, url = {://A1992HQ16800008}, author = {Le, X. C. and Cullen, W. R. and Reimer, K. J.} } @article {6778, title = {THE QUANTITATION OF BUTYLTIN AND CYCLOHEXYLTIN COMPOUNDS IN THE MARINE-ENVIRONMENT OF BRITISH-COLUMBIA}, journal = {Applied Organometallic Chemistry}, volume = {4}, number = {6}, year = {1990}, note = {ISI Document Delivery No.: EU195Times Cited: 29Cited Reference Count: 27}, month = {Nov-Dec}, pages = {581-590}, type = {Article}, abstract = {{A HPLC/GF AA procedure based on the use of C-18 columns is described for the quantitation of butyltin species in marine samples. When a mass spectrometer was used as detector (HPLC MS), evidence was obtained for the presence of other tin compounds in the samples. Extracts of samples were treated with CH3MgBr and examined by using GC MS; the presence of BU(n)SnMe4-n (n = 3-1}, keywords = {BUTYLTIN SPECIES, CYCLOHEXYLTIN SPECIES, CYHEXTIN, GC MS, HPLC AA, HPLC MS, LIQUID-CHROMATOGRAPHY, ORGANOTIN COMPOUNDS, OYSTERS, PLICTRAN, SAMPLES, SEAWATER, SPECIATION, SURFACE MICROLAYER, WATER}, isbn = {0268-2605}, url = {://A1990EU19500001}, author = {Cullen, W. R. and Eigendorf, G. K. and Nwata, B. U. and Takatsu, A.} }