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HNO3
Kinds of HNO3 Selected AbstractsAmperometric Glucose Biosensors Based on Glassy Carbon and SWCNT-Modified Glassy Carbon ElectrodesELECTROANALYSIS, Issue 1 2008Irene Carpani Abstract Different carbonaceous materials, such as single-walled carbon nanotubes (SWCNTs) and glassy carbon submitted to an electrochemical activation at +1.80,V (vs. SCE) for 900,s, have been used with the aim of comparing their performances in the development of enzyme electrodes. Commercial SWCNTs have been pretreated with 2.2,M HNO3 for 20,h prior to use. The utility of activated GC as promising material for amperometric oxidase-based biosensors has been confirmed. With glucose oxidase (GOx) as a model enzyme, glucose was efficiently detected up to 1 mM without the use of a mediator. Both electrodes operated in stirred solutions of 0.1,M phosphate buffer (pH,5.5), containing dissolved oxygen, at a potential of ,0.40,V vs. SCE. Although the performances of the two carbonaceous materials were comparable, the biosensors based on activated GC were characterized by a practically unchanged response 40 days after the fabrication, a better signal to noise ratio, and a little worse sensitivity. In addition, the preparation procedure of such biosensors was more simple, rapid and reproducible. [source] Bismuth Film Electrode as an Alternative for Mercury Electrodes: Determination of Azo Dyes and Application for Detection in Food StuffsELECTROANALYSIS, Issue 21 2007Benoît Claux Abstract Bismuth electrodes were investigated and exhibit electrochemical properties similar to mercury electrodes but with much lower toxicity. An electrochemical application of bismuth film modified glassy carbon electrode for azo dyes determination was investigated. The plating step was optimized in order to achieve its analytical efficiency. A plating potential of ,0.9,V in a solution of 200,mg/L Bi(NO3)3, 0.5,M HNO3 for 100,s yields to a suitable electrode (in terms of stability and detection). Azo dyes such as azorubine (i.e., carmoisine, E122), amaranth (E123), ponceau 4R (i.e., new coccine, E124) and allura red (E129) were determined by differential pulse voltammetry in a NaCl solution in the concentration range of few ppm to 100 ppm. The reproducibility of the signal, characterized by the relative standard deviation, was found to be less than 5%, the detection and quantification limits were few mg/L. The influence of other food components on the signal was studied and the applicability was tested on real beverages samples. [source] Speciation of selenium compounds by open tubular capillary electrochromatography-inductively coupled plasma mass spectrometryELECTROPHORESIS, Issue 21 2006Shu-Yu Lin Abstract We introduce a T-type interface and a crossflow nebulizer to find ways to combine CEC with inductively coupled plasma MS (ICP-MS) detection for selenium speciation. For CEC separation, we employed a macrocyclic polyamine-bonded phase capillary as the separation column and a bare fused-silica capillary filled with the make-up liquid (0.05,M,HNO3). The effect of nebulizer gas flow rate, make-up liquid flow, type, concentration and pH of the mobile phase on the separation have been studied. Tris buffer of 50,mM at pH,8.50 gave the best performance for selenium speciation. The reproducibility of the retention time indicated that sample injection by electrokinetic and nebulizer gas flow was better than that by self-aspiration alone. The detection limits for selenate, selenite, selenocystine and selenomethionine were found to be 2.40, 3.53, 12.86 and 11.25,ng/mL, respectively. Due to the high sensitivity and element-specific detection, as well as the high selectivity of the bonded phase, quantitative analysis of selenium speciation in urine was also achieved. [source] Variations of nitrate and sulfate in the atmosphere on days of high and low particulate mattersENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2005Chung-Yih Kuo Abstract Particulate matters with aerodynamicdiameter less than 10 ,m (PM10) were collected with high-volume samplers for four periods of consecutive samplings. Each period included a high PM10 (defined as PM10 ,110 ,g/m3) episode. The concentrations of all ionic species of high PM10 day (HPD) samples were higher than those of low PM10 (defined as PM10 < 110,g/m3) d (LPD) samples. Using the ionic concentrations of HPD samples at each station divided by those of LPD samples at respective stations, the results showed thatNO increased most from LPD to HPD among the eight ionic species examined. A high mean value (3.15) of NO/elemental carbon (EC) ratio of HPD divided by that of LPD indicates that concentration variations due to chemical formation and nonchemical factors apparently were higher than those of the concentration variations due to nonchemical factors alone. The NO/SO ratio of HPD divided by that of LPD ranged from 1.62 to 3.92 for the four periods. The results indicate that more nitrate than sulfate had formed during high PM10 episodes. Multiple linear regression analysis showed that the percentage of NH associated with nitrate and sulfate decreased and the percentage that could be explained by Ca2+ and Na+ increased on HPD. The reactions of HNO3 and H2SO4 with sea salt particles and with aqueous carbonates on soil particles during HPD were considered the main causes leading to these variations. [source] Comparative Sol,Hydro(Solvo)thermal Synthesis of TiO2 NanocrystalsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2006Xianfeng Yang Abstract Three small inorganic compounds [acetic acid (CH3COOH), nitric acid (HNO3), and hydrochloric acid (HCl)] andfive small organic compounds [n -butyl alcohol (CH3CH2CH2CH2OH), 1,2-propanediol (CH2OHCHOHCH3), propane-1,3-dicarboxylic acid (HOOCCH2COOH), butane-1,4-dicarboxylic acid (HOOCCH2CH2COOH), and ethylenediamine (H2NCH2CH2NH2)] with different donors (Cl,, NO3,, OH, COO,, and NH2) are used respectively and comparatively in different reaction media for tailoring the sol,hydrothermal synthesis of TiO2 nanocrystals at a specific reaction temperature and/or for different reaction times. Both anatase and rutile with a variety of nanostructures such as nanocubes, nanorods, nanoneedles, and their self-assembled nanospheres are selectively grown. Well-defined and crystalline anatase nanocrystals with a narrow size distribution are prepared in the presence of n -butyl alcohol. With the use of HCl, nanoneedles and their assembled nanospheres of phase-pure rutile are obtained under much less drastic conditions, even at 100 °C and for only two hours. The effects of the reaction media, synthesis temperatures, and aging times on the structures and shapes of the products are investigated in detail by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Stable Ion and Electrophilic Substitution (Nitration and Bromination) Study of A-Ring Substituted Phenanthrenes: Novel Carbocations and Substituted Derivatives; NMR, X-ray Analysis, and Comparative DNA BindingEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2007Cédric Brulé Abstract Persistent carbocations were generated from five A-ring mono- and di-substituted phenanthrenes [3-OMe; 4-OMe, 1,3-bis(OMe), 2,4-bis(OMe), and 1,3-bis(Me)]. In all cases protonation occurs in the A-ring, ortho/para relative to methoxy or methyl substituent(s). Complete NMR assignments of the resulting carbocations are reported and their charge delocalization modes are discussed. Mild nitration (with 20,50,% aqueous HNO3 at ,10 °C or at room temp.) and bromination (NBS/MeCN/room temp.) of these substrates resulted in the synthesis of several novel mononitro-/dinitro- as well as monobromo/dibromo derivatives, including those with nitro or bromo substituent in the bay-region. Correspondence between the site of attack in low-temperature protonation study and nitro substitution in ambient mild nitrations are examined. Complete NMR assignments for the new derivatives are reported as well as X-ray structures for 2,4-dimethoxy-1-nitro- and 1,3-dimethyl-4-nitrophenanthrenes. A comparative DNA binding study with MCF cells on three of the synthesized mononitro and one dinitro derivative showed that 1,3-dimethyl-9-nitro- (nitro at the meso position), 3-methoxy-4-nitro- (nitro in bay-region), and 1,3-dimethoxy-4,9-dinitrophenanthrenes (nitro in both meso and bay-regions) formed DNA adducts. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Spin- and Spray-Deposited Single-Walled Carbon-Nanotube Electrodes for Organic Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Sungsoo Kim Abstract Organic bulk-heterojunction solar cells using thin-film single-walled carbon-nanotube (SWCNT) anodes deposited on glass are reported. Two types of SWCNT films are investigated: spin-coated films from dichloroethane (DCE), and spray-coated films from deionized water using sodium dodecyl sulphate (SDS) or sodium dodecyl benzene sulphonate (SDBS) as the surfactant. All of the films are found to be mechanically robust, with no tendency to delaminate from the underlying substrate during handling. Acid treatment with HNO3 yields high conductivities >1000,S,cm,1 for all of the films, with values of up to 7694,±,800,S,cm,1 being obtained when using SDS as the surfactant. Sheet resistances of around 100,,,sq,1 are obtained at reasonable transmission, for example, 128,±,2,,,sq,1 at 90% for DCE, 57,±,3,,,sq,1 at 65% for H2O:SDS, and 68,±,5,,,sq,1 at 70% for H2O:SDBS. Solar cells are fabricated by successively coating the SWCNT films with poly(3,4-ethylenedioxythiophene):poly(styrene sulphonate) (PEDOT:PSS), a blend of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxy-carbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM), and LiF/Al. The resultant devices have respective power conversions of 2.3, 2.2 and 1.2% for DCE, H2O:SDS and H2O:SDBS, with the first two being at a virtual parity with reference devices using ITO-coated glass as the anode (2.3%). [source] Characterization of the fire environments in central offices of the telecommunications industryFIRE AND MATERIALS, Issue 3 2003Archibald Tewarson Abstract Eight free burning and two sprinklered fire tests were performed with electrical cable trays and live digital switch racks in a large enclosure to simulate telecommunications central office (TCO) fires started by electrical overheating. Very-slow-growing (non-flaming), slower-growing (partially flaming) and low-intensity-faster-growing (flaming) fires releasing gray-white, gray, and black smoke, respectively, were observed in the tests. Under quiescent conditions present in the unvented enclosure fire tests for cables, very-slow-growing fires were detected in about 1452 s, whereas the slower-growing fires were detected in about 222 s by commercial fire detectors. Under ventilation conditions typical of TCOs, detection times were very similar for the five types of commercial TCOs fire detectors used in the tests. The average detection times for slower-growing fires (cable fires) and low-intensity-faster-growing fires (digital switch rack fires) were 242±17% and 249±11%s respectively. The TCO procedures to reduce smoke damage from fires (on fire detection, inlet ventilation flow is turned off and exhaust flow is turned on) were found to be beneficial. The extent of smoke damage decreased significantly with an increase in the exhaust flow rate. The chloride ion mass deposition suggested that equipment recovery would be possible in the smoke environment if the cable vapor concentration could be reduced below about 3 g/m3. The metal corrosion rate was found proportional to the 0.6th power of the smoke concentration, similar to that found for the corrosion of metal surfaces exposed to aqueous solutions of HCl and HNO3 and for acid rain with no protective layer at the surface. Sprinkler water was found to wash down the smoke deposits on the surfaces with little indication of corrosion enhancement. Copyright © 2003 John Wiley & Sons, Ltd. [source] Quantum-Dot-Functionalized Poly(styrene- co -acrylic acid) Microbeads: Step-Wise Self-Assembly, Characterization, and Applications for Sub-femtomolar Electrochemical Detection of DNA HybridizationADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Haifeng Dong Abstract A novel nanoparticle label capable of amplifying the electrochemical signal of DNA hybridization is fabricated by functionalizing poly(styrene- co -acrylic acid) microbeads with CdTe quantum dots. CdTe-tagged polybeads are prepared by a layer-by-layer self-assembly of the CdTe quantum dots (diameter,=,3.07,nm) and polyelectrolyte on the polybeads (diameter,=,323,nm). The self-assembly procedure is characterized using scanning and transmission electron microscopy, and X-ray photoelectron, infrared and photoluminescence spectroscopy. The mean quantum-dot coverage is (9.54,±,1.2),×,103 per polybead. The enormous coverage and the unique properties of the quantum dots make the polybeads an effective candidate as a functionalized amplification platform for labelling of DNA or protein. Herein, as an example, the CdTe-tagged polybeads are attached to DNA probes specific to breast cancer by streptavidin,biotin binding to construct a DNA biosensor. The detection of the DNA hybridization process is achieved by the square-wave voltammetry of Cd2+ after the dissolution of the CdTe tags with HNO3. The efficient carrier-bead amplification platform, coupled with the highly sensitive stripping voltammetric measurement, gives rise to a detection limit of 0.52 fmol L,1 and a dynamic range spanning 5 orders of magnitude. This proposed nanoparticle label is promising, exhibits an efficient amplification performance, and opens new opportunities for ultrasensitive detection of other biorecognition events. [source] Comparison of Pb Purification by Anion-Exchange Resin Methods and Assessment of Long-Term Reproducibility of Th/U/Pb Ratio Measurements by Quadrupole ICP-MSGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2 2009Balz S. Kamber échange d'anions; purification de Pb; élimination de matrice A comparison between HBr-HCl and HBr-HNO3 based anion chemistry is presented to test the efficiency of Pb purification in the preparation of samples for isotope ratio measurement by ICP-MS. It was found that the small advantages in yield and blank offered by the HNO3 -based method were more than compensated by the more effective matrix removal of the HCl-based method. Apart from very zinc rich matrices (e.g., sphalerite), a careful single pass purification using HBr and HCl removed more than 99.9% of the matrix. In preparation for the isotope ratio analysis, a small (2,5% m/v) liquid sample aliquot was analysed to determine U, Th and Pb concentrations by solution quadrupole ICP-MS. This allowed accurate prediction of the expected ion signal and permitted optimal spiking with Tl, if desired, for mass bias correction. Long-term results for international rock reference materials showed reproducibilities of better than 1% (Th/U) and 1.5% (U/Pb). For most geological applications, such analyses obviate the need for isotope dilution concentration measurements. Les échantillons dont on veut mesurer la composition isotopique de Pb par ICP-MS sont préparés par élution sur résines anioniques. Une comparaison a été effectuée entre la chimie utilisant HBr-HCl et celle utilisant HBr-HNO3, pour vérifier leurs efficacités respectives. On montre que le léger avantage présenté par HNO3 pour ce qui concerne la qualité des blancs et le rendement était plus que compensé par la bien meilleure élimination de la matrice effectuée par la méthode utilisant HCl. A l'exception des matrices très riches en zinc (par ex sphalérite) une seule purification soigneuse avec HBr et HCl éliminait plus de 99.9% de la matrice. Pour préparer l'analyse isotopique, un petit volume (2,5% m/v) était prélevé afin d'analyser les concentrations en U, Th et Pb par ICP-MS à quadrupôle. Ceci permettait de prédire de façon précise l'intensité du signal espérée et d'optimiser la quantité de solution de spike de Tl à mettre si on souhaite corriger ainsi le biais de masse. Les résultats sur le long terme obtenus sur des roches, matériaux de référence internationale, ont montré des reproductibilités meilleures que 1% (Th/U) et 1.5% (U/Pb). Pour la plupart des applications, des analyses de cette qualité suppriment le besoin de mesures de concentrations par dilution isotopique. [source] The Direct Determination of Rare Earth Elements in Basaltic and Related Rocks using ICP-MS: Testing the Efficiency of Microwave Oven Sample Decomposition ProceduresGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2 2008Margareth S. Navarro éléments Terres Rares; attaque acide dans un four à micro onde; bombes Parr; ICP-MS; techniques de décomposition Tests are described showing the results obtained for the determination of REE and the trace elements Rb, Y, Zr, Nb, Cs, Ba, Hf, Ta, Pb, Th and U with ICP-MS methodology for nine basaltic reference materials, and thirteen basalts and amphibolites from the mafic-ultramafic Niquelândia Complex, central Brazil. Sample decomposition for the reference materials was performed by microwave oven digestion (HF and HNO3, 100 mg of sample), and that for the Niquelândia samples also by Parr bomb treatment (5 days at 200°C, 40 mg of sample). Results for the reference materials were similar to published values, thus showing that the microwave technique can be used with confidence for basaltic rocks. No fluoride precipitates were observed in the microwave-digested solutions. Total recovery of elements, including Zr and Hf, was obtained for the Niquelândia samples, with the exception of an amphibolite. For this latter sample, the Parr method achieved a total digestion, but not so the microwave decomposition; losses, however, were observed only for Zr and Hf, indicating difficulty in dissolving Zr-bearing minerals by microwave acid attack. Les Terres Rares et les éléments en trace suivants: Rb, Y, Zr, Nb, Cs, Ba, Hf, Ta, Pb, Th et U, ont été analysés par ICP-MS dans neuf matériaux de référence de composition basaltique et treize basaltes et amphibolites du Complexe basique -ultrabasique Niquelândia (centre du Brésil). Les matériaux de référence ont été mis en solution par attaque acide dans un four à micro ondes (HF et HNO3, 100 mg d'échantillon) et ceux de Niquelândia l'ont été aussi par attaque dans des bombes Parr (5 jours à 200°C, 40 mg d'échantillon). Les résultats obtenus sur les matériaux de référence sont identiques aux valeurs publiées, montrant que la technique d'attaque par micro onde peut être appliquée en toute confiance aux roches basaltiques. Aucun précipité de fluorure n'a été observé dans les solutions résultantes de l'attaque par micro onde. L'extraction des éléments a été totale, même pour Zr et Hf, pour les échantillons de Niquelândia, sauf pour une amphibole où seule la méthode d'attaque avec la bombe Parr a permis une extraction totale. Néanmoins, les pertes ne concernaient que Zr et Hf, révélant donc une certaine difficulté de la technique d'attaque par micro onde à détruire les minéraux contenant Zr. [source] Three Secondary Reference Materials for Lithium Isotope Measurements: Li7-N, Li6-N and LiCl-N SolutionsGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2007Jean Carignan matériaux de référence; isotopes de Li; solutions de Li; QUAD-ICP-MS; MC-ICP-MS The CRPG (Nancy, France) has prepared secondary reference materials for Li isotope measurements by mixing 7Li or 6Li spikes and either L-SVEC or IRMM-016 certified reference materials to produce solutions having a known Li concentration and isotopic composition. The Li7-N and Li6-N solution samples (1.5 mol l,1 HNO3) have nominal ,7Li isotopic compositions of 30.1, and -9.7, respectively relative to L-SVEC and concentrations of 100 mg l,1. Repeated measurement of these samples using the QUAD-ICP-MS at the CRPG yielded ,7Li of 30.4 ± 1.1, (n = 13) and -8.9 ± 0.9, (n = 9) at the 2s level of confidence. An additional LiCl-N solution was measured and yielded a delta value of 9.5 ± 0.6, (n = 3). Identical results were obtained at the BRGM (Orléans, France) from determinations performed with a Neptune MC-ICP-MS (30.2 ± 0.3,, n = 89 for the Li7-N, -8.0 ± 0.3,, n = 38 for the Li6-N and 10.1 ± 0.2,, n = 46 for LiCl-N at the 2s level of confidence). The deviation of measured composition relative to the nominal value for the Li6-N solution might be explained by either contamination during preparation or an error during sample weighing. These secondary reference materials, previously passed through ion exchange resin or directly analysed, may be used for checking the accuracy of Li isotopic measurements over a range of almost 40, and will be available to the scientific community upon request to J. Carignan or N. Vigier, CRPG. Le CRPG (Nancy, France) a préparé des matériaux secondaires de référence pour l'analyse des isotopes du Li en mélangeant des spikes de 7Li ou 6Li avec les matériaux de référence certifiés L-SVEC ou IRMM-016, ceci afin de produire des solutions ayant des concentrations et compositions isotopiques de Li connues. Les solutions Li7-N et Li6-N (1.5 mol l,1 HNO3) ont des compositions isotopiques nominales de ,7Li, exprimées par rapport à L-SVEC, de 30.1, et de -9.7, respectivement, et des concentrations de 10 0 mg l,1. L'analyse répétée de ces solutions par QUAD-ICP-MS au CRPG donne des ,7Li de 30.4 ± 1.1, (n = 13) et -8.9 ± 0.9, (n = 9) avec une incertitude à 2s. Une solution additionnelle de LiCl-N a été analysée et a donné une valeur de delta de 9.5 ± 0.6, (n = 3). Des résultats identiques ont été obtenus au BRGM (Orléans, France) où les déterminations ont été effectuées sur le MC-ICP-MS Neptune (30.2 ± 0.3,, n = 89 pour Li7-N, -8.0 ± 0.3,, n = 38 pour Li6-N et 10.1 ± 0.2,, n = 46 pour LiCl-N, à 2s d'intervalle de confiance). Le biais entre les compositions mesurées et la valeur nominale, observé pour la solution Li6-N peut être expliqué par une contamination durant la préparation ou par une erreur durant la pesée. Ces matériaux secondaires de référence, préalablement passés sur résine échangeuse d'ions ou analysés directement, peuvent être utilisés pour vérifier la justesse des analyses isotopiques de Li sur une gamme de presque 40% et sont à la disposition de la communauté scientifique sur demande auprès de J. Carignan ou N. Vigier, CRPG. [source] Determination of Lithium Contents in Silicates by Isotope Dilution ICP-MS and its Evaluation by Isotope Dilution Thermal Ionisation Mass SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 3 2004Takuya Moriguti Lithium; ICP-MS avec dilution isotopique; TIMS; matériaux silicatés de référence; météorites A precise and simple method for the determination of lithium concentrations in small amounts of silicate sample was developed by applying isotope dilution-inductively coupled plasma-mass spectrometry (ID-ICP-MS). Samples plus a Li spike were digested with HF-HClO4, dried and diluted with HNO3, and measured by ICP-MS. No matrix effects were observed for 7Li/6Li in rock solutions with a dilution factor (DF) of 97 at an ICP power of 1.7 kW. By this method, the determination of 0.5 ,g g -1 Li in a silicate sample of 1 mg can be made with a blank correction of < 1%. Lithium contents of ultrabasic to acidic silicate reference materials (JP-1, JB-2, JB-3, JA-1, JA-2, JA-3, JR-1 and JR-2 from the Geological Survey of Japan, and PCC-1 from the US Geological Survey) and chondrites (three different Allende and one Murchison sample) of 8 to 81 mg were determined. The relative standard deviation (RSD) was typically < 1.7%. Lithium contents of these samples were further determined by isotope dilution-thermal ionisation mass spectrometry (ID-TIMS). The relative differences between ID-ICP-MS and ID-TIMS were typically < 2%, indicating the high accuracy of ID-ICP-MS developed in this study. Nous avons développé une méthode simple et précise de détermination des concentrations en lithium dans de très petits échantillons silicatés. Elle est basée sur la méthode de dilution isotopique couplée à l'analyse par spectrométrie de masse avec couplage induit (ID-ICP-MS). Les échantillons auxquels est ajouté le spike de Li, sont mis en solution avec un mélange HF-HclO4, évaporés à sec, puis repris avec HNO3 et analysés à l'ICP-MS. Aucun effet de matrice n'est observé sur les rapports 7Li/6Li dans les solutions quand les facteurs de dilution sont 97 et qu'elles sont analysées avec une puissance du plasma de 1.7 kW. Par cette méthode, la détermination de 0.5 ,g g -1 de Li dans un échantillon silicaté de 1 mg peut être effectuée avec une correction de blanc < 1 %. Les teneurs en lithium des matériaux de référence de composition ultrabasique à acide (JP-1, JB-2, JB-3, JA-1, JA-2, JA-3, JR- 1 et JR-2 du Service Géologique du Japon, et PCC-1 du Service Géologique des USA) et de chondrites (trois échantillons différents d'Allende et un de Murchison), de poids variant entre 8 et 81 mg ont été déterminées. La déviation standard relative typique était < 1.7%. Les teneurs en lithium de ces échantillons ont été ensuite mesurées par dilution isotopique et spectrométrie de masse à thermo-ionisation (ID-TIMS). Les différences entre les résultats obtenus par ID-ICP-MS et ID-TIMS étaient < 2%, démontrant ainsi la grande justesse de la technique ID-ICP-MS développée dans cette étude. [source] Determination of Selenium Concentration in Sixty Five Reference Materials for Geochemical Analysis by GFAAS after Separation with Thiol CottonGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2-3 2001Luc Marin sélénium; SAA four graphite; séparation; matériaux géologiques de référence; coton thiol Selenium has been determined in sixty five geological reference materials of different origins by graphite furnace atomic absorption spectrometry. Samples were decomposed with a mixture of nitric and hydrofluoric acids. Selenium was reduced to SeIV with hydrochloric acid, and then fixed and separated from the matrix on thiol cotton. After digestion of the thiol cotton in hot nitric acid, the Se concentration was measured using palladium and magnesium nitrates as a matrix modifier. The limit of determination was 0.02 ,g g,1, the precision of the results (relative standard deviation of 3 to 8 replicates) varied from 2.6 to 17.7% with an average of 7.9% in the range 0.02-42.7 ,g g,1 and was similar to the value obtained for synthetic samples. Our results are in good agreement with available literature values. Le sélénium a été dosé sur 65 standards géochimiques de référence de différentes provenances par spectrométrie d'absorption atomique avec four graphite. Les échantillons ont été mis en solution par une attaque acide HNO3 -HF. Le sélénium a été réduit en SeIV avec de l'acide chlorhydrique, fixé et séparé de la matrice sur du coton thiol. Après décomposition du coton thiol par chauffage avec de l'acide nitrique, les concentrations en sélénium ont été mesurées en utilisant du nitrate de palladium et de magnésium comme modificateur de matrice. La limite de détermination est de 0.02 ,g g,1, la précision des résultats (écart type relatif sur 3 à 8 mesures) pour les standards géochimiques varie de 2.6 à 17.7% avec une moyenne de 7.9% dans la game 0.02-42.7 ,g g,1et est comparable à celle obtenue pour des échantillons synthétiques. Nos résultats sont en bonne concordance avec les résultats déjà publiés dans la littérature. [source] Desorption kinetics of model polar stratospheric cloud films measured using Fourier Transform Infrared Spectroscopy and Temperature-Programmed DesorptionINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2001Birgit G. Koehler This study combines Fourier transform infrared (FTIR) spectroscopy and temperature-programmed desorption to examine the evaporation kinetics of thin films of crystalline nitric acid hydrates, solid amorphous H2O/HNO3 mixtures, H2O,ice, ice coated with HCl, and solid HNO3. IR spectroscopy measured the thickness of each film as it evaporated, either at constant temperature or during a linear temperature ramp (temperature-programmed infrared, TPIR). Simultaneously, a mass spectrometer measured the rate of evaporation directly by monitoring the evolution of the molecules into the gas phase (temperature-programmed desorption, TPD). Both TPIR and TPD data provide a measurement of the desorption rate and yield the activation energy and preexponential factor for desorption. TPD measurements have the advantage of producing many data points but are subject to interference from experimental difficulties such as uneven heating from the edge of a sample and sample-support as well as pumping-speed limitations. TPIR experiments give clean but fewer data points. Evaporation occurred between 170 and 215 K for the various films. Ice evaporates with an activation energy of 12.9 ± 1 kcal/mol and a preexponential factor of 1 × 1032±1.5 molec/cm2 s, in good agreement with the literature. The beta form of nitric acid trihydrate, ,,NAT, has an Edes of 15.6 ± 2 kcal/mol with log A = 34.3 ± 2.3; the alpha form of nitric acid trihydrate, ,,NAT, is around 17.7 ± 3 kcal/mol with log A = 37.2 ± 4. For nitric acid dihydrate, NAD, Edes is 17.3 ± 2 kcal/mol with log A = 35.9 ± 2.6; for nitric acid monohydrate, NAM, Edes is 13 ± 3 kcal/mol with log A = 31.4 ± 3. The ,,NAT converts to ,,NAT during evaporation, and the amorphous solid H2O/HNO3 mixtures crystallize during evaporation. The barrier to evaporation for pure nitric acid is 14.6 ± 3 kcal/mol with log A = 34.4 ± 3. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 295,309, 2001 [source] Computational study on the comparative synthesis of energetic FOX-7 derivativesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4 2010Min-Hsien Liu Abstract Ethene and two kinds of nitrating reagents (HNO3 and N2O5) were included in respective molecular systems, which progressed through a two-stage electrophilic and free radical nitrosubstitution, resulting in the corresponding nitroethene compounds. Subsequent halogenation (using Cl2 and Br2) and amination (using ammonia) were then performed, also by electrophilic and radical substitution, to produce the target 1,1-diamino-2,2-dinitroethene (FOX-7) derivatives. All transition state species were identified using a two- or three-structure Synchronous Transit-Guided Quasi-Newton between the Cartesian coordinates of the related molecular systems at specific reaction stages. The modeling results suggest that N2O5 is the better agent for nitration and bromine is suitable for use in halogenation. The comparable activation energies throughout the reaction stages were considered to imply the most feasible pathways of FOX-7 synthesis. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Nitric Acid Dissociation at an Aqueous Surface: Occurrence and MechanismISRAEL JOURNAL OF CHEMISTRY, Issue 2 2009Shuzhi Wang Here we briefly review some highlights of our recent work on the acid dissociation of nitric acid HNO3 at an aqueous surface, a proton transfer reaction of interest not only from a fundamental perspective, but also in connection with heterogeneous chemistry in a wide range of atmospheric contexts. Two types of studies of the potential acid dissociation are discussed, quantum chemical reaction path calculations to assess the reaction free energy and Car-Parrinello molecular dynamics simulations to assess the reaction feasibility. We discuss the agreement and disagreement between the predictions of these two calculations as a function of the initial location of the HNO3 molecule, ranging from a positioning on top of the aqueous surface to one several water layers below the surface. Special attention is given to the four key water solvent motions found to be necessary for the proton transfer reaction to occur. Finally, an Eigen cation, rather than a Zundel cation, is in all cases found to be predominant next to the nitrate ion in contact ion pairs produced in the acid dissociation. This predominance remains, although diminished, for solvent-separated ion pairs. [source] Preconcentration and matrix elimination for the determination of Pb(II), Cd(II), Ni(II), and Co(II)by 8-hydroxyquinoline anchored poly(styrene-divinylbenzene) microbeadsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Hakan A Abstract Poly(styrene-divinylbenzene), PS-DVB, microbeads were modified with 8-hydroxyquinoline (8-HQ) following nitration, reduction of NO2 to NH2, and conversion of NH2 to diazonium salt. Characterization of pristine, NO2, NH2, NN+Cl,, and 8-QH functional groups modified microbeads was made by Fourier transform-infrared spectrometry (FTIR) and porosimetry. Total reflectron-X-ray florescence spectrometer (TXRF) was used to test the affinity of the 8-HQ modified microbeads to toxic metal ions. 8-HQ-modified microbeads were used to examine the adsorption capacity, recovery, preconcentration, and the matrix elimination efficiency for Pb(II), Cd(II), Ni(II), and Co(II) ions as a function of changing pH, initial metal-ion concentrations, and also equilibrium adsorption time of the studied metal ions. Preconcentration factors for the studied toxic metal ions were found to be more than 500-fold and recovery between 93.8% and 100.6%. Ultratrace toxic metal-ion concentrations in sea water were determined easily by using modified microbeads. Reference sea-water sample was used for the validation of the method, and it was found that recovery, preconcentration, and the matrix elimination were performed perfectly. For the desorption of the toxic metal ions, 3M of HNO3 was used and desorption ratio shown to be more than 96%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Aluminum Content in Foods and Beverages Consumed in the Spanish DietJOURNAL OF FOOD SCIENCE, Issue 2 2000F.F. López ABSTRACT: A reliable and rapid method for determining aluminum content in foods and beverages was developed using electrothermal atomization-atomic absorption spectrometry (ETA-AAS) using previous optimization of the time-temperature program for the graphite furnace. The samples were subjected to acid mineralization with HNO3 and V2O5. The technique used slurries for assay in samples of dairy products. The detection limit was 4.0 pg. The mean recovery obtained ranged from 98.5% to 99.0%. The variation coefficient ranged from 3.2% to 5.2%. The results obtained ranged from 1.362 to 6.610 ,g/g in seafood, 0.171 to 29.688 ,g/g in vegetables, 19.560 to 70.100 ,g/g in olive oil, 0.424 to 6.430 ,g/g in dairy products and 25.600 to 58.057 ,g/g in stimulant drinks and infusions. This study contributes new data on the Al content of a variety of foods and beverages in Spain and such data are important for composition tables. The higher presence corresponded to seafood, vegetables and dairy products. Their contribution to Al dietary intake were estimated. [source] Chromatographic partitioning of cesium by a macroporous silica-calix[4]arene-crown supramolecular recognition compositeAICHE JOURNAL, Issue 10 2010Anyun Zhang Abstract A macroporous silica-based 1,3-[(2,4-diethyl-heptylethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14) supramolecular recognition polymeric composite, (Calix[4]+Oct)/SiO2 -P, was synthesized. It was performed by impregnating and immobilizing Calix[4]arene-R14 and n -octanol into the pores of the macroporous SiO2 -P particles support. n -Octanol was used to modify Calix[4]arene-R14 through hydrogen bonding. The effect of eight typical fission products contained in highly active liquid waste (HLW) on the adsorption of Cs(I), one of the heat generators, was investigated at 298 K by examining the effect of contact time and the HNO3 concentration in a range of 0.3,7.0 M. (Calix[4]+Oct)/SiO2 -P showed excellent adsorption ability and high selectivity for Cs(I) at 4.0 M HNO3 over the tested elements. The partitioning of Cs(I) from a simulated HLW was operated by (Calix[4]+Oct)/SiO2 -P packed column. Cs(I) was able to be effectively eluted by water and separated from the tested metals. It is demonstrated that (Calix[4]+Oct)/SiO2 -P is promising to apply in chromatographic separation of Cs(I) from HLW. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Toward greener separations of rare earths: Bifunctional ionic liquid extractants in biodieselAICHE JOURNAL, Issue 9 2010Yinghui Liu Abstract Ionic liquids (ILs) containing quaternary phosphonium cations and phosphonic acid anions were explored as novel extractants for rare earths (RE) separation. They were considered to be bifunctional ionic liquid extractants (bif-ILEs), since both cations and anions of ILs were involved in the extraction. Trihexyl(tetradecyl)phosphonium bis 2,4,4-trimethylpentylphosphinate (Cyphos IL 104), as a bif-ILE, together with propylene carbonate (PC), dimethyl carbonate (DMC), and soybean oil methyl ester (SBME, biodiesel) as diluents was employed in the extraction of RE(III) from aqueous solutions. Acidified Cyphos IL 104 (HNO3 -Cyphos IL 104) exhibited high solubility in three diluents, and higher extraction efficiency than bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) because of the coextraction of RE(III) by quaternary phosphonium cation and phosphonic acid anion in organic phase. Additionally, this coextraction mechanism could eliminate the loss of IL. The physical properties and miscibility test results indicated that SBME was an excellent solvent for RE(III) extraction. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] A bi-order kinetic model for poly(methyl methacrylate) decomposition in HNO3 using microwave irradiationAICHE JOURNAL, Issue 8 2009Chun-Chih Lin Abstract In this study, a novel bi-order model combined with zero- and first-order kinetics was proposed for the decomposition of PMMA (MW = 120,000 g/mol) in concentrated HNO3 by microwave irradiation. To develop and validate this model, Fourier Transform Infrared spectroscopy, scanning electron microscopy, fractional-life method, the gravimetric analysis and Newton's method were utilized. Rate constants, activation energies, the pre-exponential factors and the weight fractions (,) via main-chain scission for the decomposition at 423,453 K were derived from this model. The zero-order reaction was observed dominant at 423,443 K, while the first-order reaction dominated at 453 K and 473 K. The digestion efficiency increased as HNO3 was increased to >3 mL at 423 K,443 K. At 473 K, the digestion was almost 100% when HNO3 volume was >3 mL. The estimated , values increased with HNO3 volume at 423 and 443 K, but varied insignificantly at 453 and 473 K. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] A Study on the Effect of Template Chain Length on the Synthesis of Mesoporous Silica in An Acidic ConditionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Yang Yu-Xiang Hexagonal mesoporous silica materials were synthesized in an acidic medium using different chain length of the quaternary ammonium surfactants as a template. The effects of chain length on the physical property, morphology of mesoporous materials, and the temperature on synthesis of materials in CnTMBr,TEOS,HNO3,H2O (n=12,14,16,18) system were systematically studied. The synthesized products were characterized by X-ray diffraction patterns, scanning electron microscopy, transmission electron microscopy, and nitrogen sorption analysis. It was found that degree of ordering, the d spacing values, and pore size all increase with an increase in the chain length of the template. The optimum synthesis temperature for mesoporous silica using C18TMBr,TEOS,HNO3,H2O system is slightly higher than the Krafft point. The temperature and pH can all affect the expandability of micelles, and so an increase in temperature and decrease in pH all lead to an increase in the pore size. It is also found that the shear flow and chain length are two key factors inducing the formation of millimeter-scaled silica ropes and micrometer-scaled rope fibers. [source] Synthesis of Bismuth Sodium Titanate Nanosized Powders by Solution/Sol,Gel ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2003Chang Yeoul Kim (Bi1/2Na1/2)TiO3 (BNT) is a prominent candidate for a lead-free piezoelectric material. In this study, BNT was synthesized using the solution/sol,gel method, in which a solution of Bi2O3 and Na2CO3 was dissolved in HNO3 as starting materials. The solution then was mixed with ethylene glycol and titanium tetraisopropoxide. The obtained BNT powder was analyzed using FT-IR, DTA-TG, Raman spectroscopy, and high-temperature XRD. Results showed that BNT crystallization occurred above 600°C. TEM investigation showed that 100,200 nm BNT particles were formed by heat-treating the sol,gel-derived BNT sol at 700°C for 6 h. [source] Influence of Diaspore Seeding and Chloride Concentration on the Transformation of "Diasporic" Precursors to CorundumJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2001Richard L. Smith "Diasporic" precursors derived from sols formed by the controlled hydrolysis of aluminum sec-butoxide in the presence of HCl yielded mixtures of corundum and amorphous alumina when calcined between 500° and 800°C. The fraction of corundum in the calcined products depended on the HCl/alkoxide ratio used during hydrolysis and was maximized at 64 wt% when the molar ratio was 1. Precursors formed from sols hydrolyzed in the presence of HNO3 rather than HCl yielded only amorphous products or transition aluminas when treated below 900°C. The corundum yield of the precursors was enhanced when they were seeded with diaspore (,-AlOOH) crystals. Precursors synthesized with an HCl/alkoxide ratio of 1 and seeded with 7.6 × 1016 diaspore seeds/(mol of Al2O3) were transformed to phase-pure corundum within 12 h at 700°C. Based on studies of the phase evolution of the precursors during calcining, it was concluded that the diaspore seeds promoted conversion by acting as corundum nuclei once they decomposed at ,450°C. [source] Determination of iron in blood serum using ,ow injection with luminol chemiluminescence detectionLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 6 2004A. Waseem Abstract A simple and rapid ,ow injection method is reported for the determination of iron in blood serum after acid digestion with HNO3 and HClO4, based on luminol CL detection in the absence of added oxidant. The detection limit (3 s) was 1.0 nmol/L with a sample throughput of 120/h. The calibration graph was linear over the range 0.001,1.0 µmol/L (r2 = 0.9974), with relative standard deviations (RSD) (n = 4) in the range 3.2,5%. The effect of interfering cations (Ca(II), Mg(II), Cu(II), Cd(II), Pb(II), Mn(II), Zn(II), Ni(II), Co(II) and Fe(III)) and anions (Cl,, SO42,, HCO3,, NO3,, NO2,) were studied using a luminol CL system for Fe(II) determination. The method was applied to normal blood serum and the results (1.32 ± 0.08,1.74 ± 0.05 mg/L) were compared with those from a spectrophotometric reference method (1.34 ± 0.06,1.80 ± 0.10 mg/L), which agree fairly well with the overall reference range in blood. Copyright © 2004 John Wiley & Sons, Ltd. [source] Measurement of trace atmospheric species by chemical ionization mass spectrometry: Speciation of reactive nitrogen and future directionsMASS SPECTROMETRY REVIEWS, Issue 2 2007L. Gregory HueyArticle first published online: 22 JAN 200 Abstract Chemical ionization mass spectrometry (CIMS) has proven to be a powerful method for sensitive, fast time response (t,1 sec) measurements of various atmospheric compounds with limits of detection (LOD) of the order of tens of pptv and lower. The rapid time response of CIMS is particularly well suited for airborne measurements and its application has largely grown out of airborne measurements in the stratosphere and upper troposphere. This work reviews some of the advances in CIMS technology that have occurred in the past decade. In particular, CIMS methods for selective measurement of reactive nitrogen species (e.g., HNO3, HO2NO2, PAN, and NH3) in the lower atmosphere (altitudes ,0,8 km) are described. In addition, recent developments in CIMS technology for the selective measurement of gas-phase hydroperoxides and aerosol chemical composition are briefly described. © 2007 Wiley Periodicals, Inc., Mass Spec Rev 26:166,184, 2007 [source] Materials and Corrosion 9/2010MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2010Article first published online: 2 SEP 2010 Cover: Metallic structure of X1NiCrMoCu32-28-7 (UNS N08031, alloy 31, 1.4562) welded with SG-NiCr23Mo16 (FM 59, 2.4607) after 4 weeks in the vapor phase of nitrating acid (mixture of 66 % HNO3, 34 % H2SO4) at 55 °C. No further treatment of the surface was made. Corrosion behavior was investigated at BAM, the Federal Institute for Materials Research and Testing, in order to extend the BAM-List, where the suitability of materials for transport tanks carrying Dangerous Goods is evaluated. More detailed information can be found in: R. Bäßler. M. Weltschev, H. Alves, M. Langer, Corrosion Resistance of Alloy 31 and 59 in Highly Corrosive Dangerous Goods, Proceedings NACE International Corrosion Conference 2010 San Antonio, paper 10340. [source] Materials and Corrosion 8/2010MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 8 2010Article first published online: 2 AUG 2010 Cover: Metallic structure of X1NiCrMoCu32-28-7 (UNS N08031, alloy 31, 1.4562) welded with SG-NiCr23Mo16 (FM 59, 2.4607) after 4 weeks in the vapor phase of nitrating acid (mixture of 66 % HNO3, 34 % H2SO4) at 55 °C. No further treatment of the surface was made. Corrosion behavior was investigated at BAM, the Federal Institute for Materials Research and Testing, in order to extend the BAM-List, where the suitability of materials for transport tanks carrying Dangerous Goods is evaluated. More detailed information can be found in: R. Bäßler. M. Weltschev, H. Alves, M. Langer, Corrosion Resistance of Alloy 31 and 59 in Highly Corrosive Dangerous Goods, Proceedings NACE International Corrosion Conference 2010 San Antonio, paper 10340. [source] Materials and Corrosion 7/2010MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 7 2010Article first published online: 19 JUL 2010 Cover: Metallic structure of X1NiCrMoCu32?28?7 (UNS N08031, alloy 31, 1.4562) welded with SG-NiCr23Mo16 (FM 59, 2.4607) after 4 weeks in the vapor phase of nitrating acid (mixture of 66 % HNO3, 34 % H2SO4) at 55 °C. No further treatment of the surface was made. Corrosion behavior was investigated at BAM, the Federal Institute for Materials Research and Testing, in order to extend the BAM-List, where the suitability of materials for transport tanks carrying Dangerous Goods is evaluated. More detailed information can be found in: R. Bäßler. M. Weltschev, H. Alves, M. Langer, Corrosion Resistance of Alloy 31 and 59 in Highly Corrosive Dangerous Goods, Proceedings NACE International Corrosion Conference 2010 San Antonio, paper 10340. [source] | |||||||||||||||||||||||||||||||