Some interference effects occurring in the hydrogen/argon/entrained-air flame

An examination was made of the effects of various cations and anions on the determinations of calcium (4227 Å) by flame emission using turbulent hydrogen/ argon/entrained-air and hydrogen/oxygen flames. The effects of height of observation and mechanisms of interference are discussed for Cs⁺, Rb⁺, F^-, Br^-, I^-, NO₃^-, Cl0₄^-, S0₄^2-, PO₄^3-, P₂O₇^4-, acetate, oxalate, citrate, tartrate and EDTA. Ionization interferences were not detected in the hydrogen/argon/entrained-air flame, but all other types of interference were more serious with this flame than with the hydrogen/ oxygen flame. The study also suggests some methods by which the effects of the interferences may be overcome.     

NaBaPOM4:Tb3+绿色荧光粉制备及其发光特性

采用高温固相法合成了NaBaPOM₄:Tb³⁺绿色荧光粉, 并研究了材料的发光性质. NaBaPOM₄:Tb³⁺材料呈多峰发射, 发射峰位于437、490、543、587和624 nm, 分别对应Tb³⁺的⁵D₃→⁷F₄和⁵D₄→⁷F_{J=6, 5, 4, 3}跃迁发射, 主峰为543 nm; 监测543 nm发射峰, 所得激发光谱由4f⁷5d¹宽带吸收(200-330 nm)和4f-4f 电子吸收(330-400 nm)组成, 主峰为380 nm. 研究了Tb³⁺掺杂浓度, 电荷补偿剂Li⁺、Na⁺、K⁺和Cl^-, 及敏化剂Ce³⁺对NaBaPOM₄:Tb³⁺材料发射强度的影响. 结果显示: 调节激活剂浓度、添加电荷补偿剂或敏化剂均可以在很大程度上提高材料的发射强度.     

Elimination of anionic interference in flame photometric determination of calcium in the presence of phosphate and sulphate

Studies on the interference of phosphate and sulphate in the flame emission of calcium as calcium chloride have shown that there is a fall of intensity corresponding initially to the quantity of the interfering anion, the emission intensity reaching a constant value at a certain ratio of PO₄^-3 or SO₄^-2 to Ca⁺².On addition of appropriate quantities of lanthanum (or iron) to the sample, the intensity of the calcium emission lines is restored to the value it had when the interfering anions were absent.It is postulated that lanthanum replaces calcium in a phosphate- or sulphate-containing compound, that without lanthanum does not form calcium ions even at high temperature.     

Optical Sensing of Cesium Using 1,3-Alternate Calix[4]-mono- and Di(anthrylmethyl)aza-crown-6

We have synthesized two derivatives of alkylanthracene covalently bonded to 1,3-alternate calix[4]aza-crown-6 at the nitrogen position to study the effect of alkali metal ion complexation on the emission properties of anthracene fluorophore. The mono- and dianthryl-substituted probes are weakly fluorescent because their emission is partially quenched by photoinduced electron transfer (PET) from the nitrogen lone pair to the excited singlet state of anthracene. Upon complexation of alkali metal ions (e.g. K⁺, Cs⁺) by the crown moiety, the nitrogen lone pair can no longer participate in the PET process causing an enhancement in the emission of anthracene fluorophore (fluorescent turn on). The maximum fluorescence enhancement observed upon complexation of cesium ions by mono- and dianthryl-substituted calix[4]aza-crown-6 relative to the uncomplexed form was 8.5- and 11.6-fold, respectively.     

Study of quenching of S2 emission by addition of oxygen to a hydrogen flame in molecular emission cavity analysis

Interferences of oxygen on S₂ emission were measured for a hydrogen-oxgen flame in molecular emission cavity analysis and are discussed in terms of the emission intensities and temperatures in different regions of the flame. When a little oxygen is added to a hydrogen flame, S₂ emission is usually quenched. It also brings about a reduction in temperature in the lower region of the flame, where a cavity is introduced. However, in a “lower burnt hydrogen-oxygen flame”, in which hydrogen reacts instantly with added oxygen at the burner top, S₂ emission is not quenched by addition of oxygen, and the intensity and the flame temperature increase linearly with increasing oxygen flow-rate. Therefore, it is apparent that an increase in flame temperature is not responsible for the quenching. It is suggested that the existence of unburnt oxygen in the lower region of the flame can cause the quenching owing to the destruction of S₂ molecules to form sulphur-oxygen compounds.     

Study of gas‐phase reactions of NO2+ with aromatic compounds using proton transfer reaction time‐of‐flight mass spectrometry

The study of ion chemistry involving the NO₂⁺ is currently the focus of considerable fundamental interest and is relevant in diverse fields ranging from mechanistic organic chemistry to atmospheric chemistry. A very intense source of NO₂⁺ was generated by injecting the products from the dielectric barrier discharge of a nitrogen and oxygen mixture upstream into the drift tube of a proton transfer reaction time‐of‐flight mass spectrometry (PTR‐TOF‐MS) apparatus with H₃O⁺ as the reagent ion. The NO₂⁺ intensity is controllable and related to the dielectric barrier discharge operation conditions and ratio of oxygen to nitrogen. The purity of NO₂⁺ can reach more than 99% after optimization. Using NO₂⁺ as the chemical reagent ion, the gas‐phase reactions of NO₂⁺ with 11 aromatic compounds were studied by PTR‐TOF‐MS. The reaction rate coefficients for these reactions were measured, and the product ions and their formation mechanisms were analyzed. All the samples reacted with NO₂⁺ rapidly with reaction rate coefficients being close to the corresponding capture ones. In addition to electron transfer producing [M]⁺, oxygen ion transfer forming [MO]⁺, and 3‐body association forming [M·NO₂]⁺, a new product ion [M−C]⁺ was also formed owing to the loss of C═O from [MO]⁺.This work not only developed a new chemical reagent ion NO₂⁺ based on PTR‐MS but also provided significant interesting fundamental data on reactions involving aromatic compounds, which will probably broaden the applications of PTR‐MS to measure these compounds in the atmosphere in real time.     

Spectrophotometric determination of osmium : O-Aminophenol-p-sulphonic acid as a reagent

o-Aminophenol-p-sulphonic acid is suggested as a very sensitive reagent for spectrophotometric determination of osmium (VI) and (VIII) at pH 2 5–4. The absorption maximum is at 440 mμ and the optimum concentration range is from 2 to 8 p p m of osmium Moderate amounts of Pd⁺², lr⁺⁴, WO₄^-2, Cr⁺³, Zn⁺², Zr⁺⁴, Mg⁺², Ba⁺² and Sr⁺² do not interfere     

Effect of the Support on the Nature of Metal-Promoter Interactions in Ru-Cs<Superscript>+</Superscript>/MgO and Ru-Cs<Superscript>+</Superscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts for Ammonia Synthesis

The Ru-Cs⁺/MgO and Ru-Cs⁺/γ-Al₂O₃ catalysts, which were prepared by an impregnation method using RuOHCl₃ and Cs₂CO₃ as precursor compounds and reduced with H₂ at 450°C, are characterized by X-ray diffraction, high-resolution transmission electron microscopy (with X-ray microanalysis), and X-ray photoelectron spectroscopy (XPS). The Cs⁺/MgO(Al₂O₃) systems, Ru-Cs⁺ black, and model systems prepared by cesium sputtering onto polycrystalline ruthenium foil are studied as reference samples. It is found that, in the Ru-Cs⁺/MgO sample, cesium is present as a Cs_{2 + x}O cesium suboxide, which weakly interacts with the support, localized on the surface of Ru particles or near them. In the case of Ru-Cs⁺/γ-Al₂O₃, cesium occurs as a species that is tightly bound to the support; this is likely surface cesium aluminate, which prevents promoter migration to Ru particles. The Ru-Cs⁺/MgO sample exhibits a considerable shift of the Ru3d line in the XPS spectra toward lower binding energies, as compared to the bulk metal. It is hypothesized that this shift is due to a decrease in the electron work function from the surface of ruthenium because of the polarizing effect of Cs⁺ ions in contact with Ru particles. Based on the experimental results, the great difference between the catalytic activities of the Ru-Cs⁺/MgO and Ru-Cs⁺/γ-Al₂O₃ systems in ammonia synthesis at 250–400°C and atmospheric pressure is explained.     

Preparation and Characterization of Storage and Emission Functional Material of Cs2O-doped 12CaO·7Al2O3

We provides a novel approach to generate low-temperature atomic oxygen anions (O^-) emis-sion using the cesium oxide-doped 12CaO·7Al₂O₃ (Cs₂O-doped C12A7). The maximal emis-sion intensity of O^- from the Cs₂O-doped C12A7 at 700 oC and 800 V/cm reached about 0.54 μA/cm², which was about two times as strong as that from the un-doped C12A7(0.23 μA/cm²) under the same condition. The initiative temperature of the O^- emission from the Cs₂O-doped C12A7 was about 500 oC, which was also much lower than the initiative temperature from the un-doped C12A7 (570 oC) in the given field of 800 V/cm. High pure O^- emission close to 100% could be obtained from the Cs₂O-doped C12A7 under the lower temperature (<550oC). The emission features of the Cs₂-doped C12A7, including the emis-sion distribution, temperature effect, and emission branching ratio have been investigated in detail and compared with the un-doped C12A7. The structure and storage characteristics of the resulting material were also investigated via X-ray diffraction and electron paramag-netic resonance. It was found that doping Cs₂ to C12A7 will lower the initiative emission temperature and enhance the emission intensity.     

Excitation and decay of the C2Σ+u state of N+2 following collisions of He+ ions with N2 isotopes

A quantitative analysis is made of the N⁺₂ “2nd negative” emission (“2N”: C²Σ⁺_u → X²Σ⁺_g) produced by the impact of 500 eV to 25 keV He⁺ beams on ¹⁴N₂, ¹⁴N¹⁵N and ¹⁵N₂. Above about 5 keV, the relative 2N emission rates from the various vibrational levels of the C state are the same as those observed for ? 2 keV Ne⁺, or > / 90 eV electron-impact. These limiting distributions are compared to those predicted for a Franck-Condon excitation of the C state, modified by configuration interaction. The weakening in 2N emission at the vibrational levels ν′ > / 3 is ascribed to spontaneous C-state predissociation. The data fully confirm recent reports that this predissociation extends over a wide range of ν′ and that it is subject to a strong isotope effect. The ratios of the rates of C-state predissociation to 2N emission are obtained for the levels ν′ = 3 to 8 of each nitrogen isotope. By means of these data it is shown that near-resonant charge transfer dominates the distribution of vibrational excitation probabilities only at energies below about 10 eV. A comparison is made of absolute cross-sections for C-state emission with those for N⁺ and N⁺₂ production in He⁺/¹⁴N₂ collisions at energies between 5.5 eV and 25 keV.     

Sorption of cesium from water solutions on potassium nickel hexacyanoferrate-modified <Emphasis Type="Italic">Agaricus bisporus</Emphasis> mushroom biomass

In order to gain biosorbent that would have the ability to bind cesium ions from water solution effectively, potassium nickel hexacyanoferrate(II) (KNiFC) was incorporated into the mushroom biomass of Agaricus bisporus. Cesium sorption by KNIFC-modified A. bisporus biosorbent was observed in batch system, using radiotracer technique using ¹³⁷Cs radioisotope. Kinetic study showed that the cesium sorption was quite rapid and sorption equilibrium was attained within 1 h. Sorption kinetics of cesium was well described by pseudo-second order kinetics. Sorption equilibrium was the best described by Freundlich isotherm and the distribution coefficient was at interval 7,662–159 cm³ g⁻¹. Cesium sorption depended on initial pH of solution. Cesium sorption was very low at pH₀ 1.0–3.0. At initial pH 11.0, maximum sorption of cesium was found. Negative effect of monovalent (K⁺, Na⁺, NH₄ ⁺) and divalent (Ca²⁺, Mg²⁺) cations on cesium sorption was observed. Desorption experiments showed that 0.1 M potassium chloride is the most suitable desorption agent but the complete desorption of cesium ions from KNiFC-modifed biosorbent was not achieved.     

Electroreduction of Oxalate Complexes of Ruthenium(III) on a Dropping Mercury Electrode: Effect of Alkali Metal Cations and Solution Acidity

It is established that the reaction of recharging trioxalate complexes of ruthenium(III) occurs in the case of solutions with excess supporting oxalate salts of alkali metals K⁺, Na⁺, and Cs⁺ in reversible conditions, and limiting recharge currents are caused by diffusion. At the same time, values of diffusion coefficients for complex anion [Ru(C₂O₄)₃]^–3 decrease by almost two times upon going from potassium to sodium and cesium electrolytes. Substantial differences in the limiting currents in solutions containing excess amounts of the above salts are explained by the formation, at least in the case of cesium and sodium electrolytes, of ionic associates whose reduction rate at a fixed potential is lower than that of nonassociated anion [Ru(C₂O₄)₃]^–3. With solution dilution by supporting salts, transition is observed from reversible recharge conditions to absolutely irreversible conditions and a change in the above sequence of the effect of supporting cations on the recharge rate; at a fixed potential, the process decelerates in the series Cs⁺ > K⁺ > Na⁺. The reduction wave of the ruthenium(II) oxalate complexes in solutions with excess supporting electrolyte happens to depend on pH and, probably, is determined by simultaneous formation of adsorbed atoms of hydrogen (or ruthenium hydride) on atoms of ruthenium(0).     

Excitation of Species in an Expanded Argon Microwave Plasma at Atmospheric Pressure

The excitation capability of an argon microwave plasma flame expanded at atmospheric pressure has been studied. For this purpose, argon with different proportions of nitrogen was introduced at the end of the expanded flame, where the population densities of the atomic argon levels were still high enough. Optical emission spectra allowed the identification of different excited species in the plasma. When argon containing nitrogen was added at the end of the plasma flame, all argon lines emitted in this region were highly quenched, emission due to species containing nitrogen (NH, CN) was enhanced and a noticeable increase in the emission of N₂ (C ³Π_u ? B ³Π_g) was observed. On the contrary, the weak emission of $ {\text{N}}_{2}^{ + } \left( {B^{ 2} \sum_{u}^{ + } - X^{ 2} \sum_{g}^{ + } } \right) $ was scarcely affected. According to these results it is possible to conclude that metastable argon atoms from the expanded flame are the main energy carriers when generating N₂ reactive species in this plasma zone.     

The Influence of Small Hydrogen Admixtures up to 5?% to a Low Pressure Nonuniform Microwave Discharge in Nitrogen

We present the results of spectroscopic and 2D modeling study of the influence of hydrogen addition to non-uniform nitrogen plasma of electrode microwave discharge. The axial intensity distributions of the H_?? line and N₂ (2⁺: C³??_u????B³??_g, 1⁺: B³??_g????A³?? _u ⁺ ) and N₂ ⁺ (1^?: B²?? _u ⁺ ???X²?? _g ⁺ ) molecular bands are recorded for different incident microwave power input and hydrogen content. The corona model is used to determine electric field strength in nitrogen discharge from the intensity ratio of 2⁺ and 1^? system of nitrogen bands. By means of 2D modeling spatial distributions of nitrogen molecules in C³??_u state, microwave field strength, electron density, concentrations of N₂ ⁺, N₄ ⁺ are determined in nitrogen and in nitrogen?Chydrogen mixtures. The concentration of N₂H⁺ ions in nitrogen?Chydrogen mixtures is determined also. The general conclusion of 2D modeling is in agreement with experimental results and shows that the influence of hydrogen addition to discharge is related to the fast conversion reactions of nitrogen ions (N₂ ⁺, N₄ ⁺) to N₂H⁺ ion. These ion conversions lead to the change of ion plasma components transport properties, to the modification of microwave field strength in plasma, and consequently, to the alternation of all plasma parameters.     

The effect of the synthesis method on the parameters of pore structure and selectivity of ferrocyanide sorbents based on natural minerals

Ferrocyanide sorbents were obtained via thin-layer and surface modification of natural clinoptilolite and marl. The effect of modification method on surface characteristics of these sorbents and their selectivity for cesium was studied. It was shown that the modification resulted in an increase of selectivity of modified ferrocyanide sorbents to cesium as compared with the natural clinoptilolite in presence of Na⁺, as well as in an increase of cesium distribution coefficients in presence of K⁺. The nickel–potassium ferrocyanide based on the clinoptilolite showed the highest selectivity for cesium at sodium concentrations of 10^?4—2 mol L^?1: cesium distribution coefficient was lg K _d = 4.5 ± 0.4 L kg^?1 and cesium/sodium separation factor was α(Cs/Na) = 250. In the presence of NH₄ ⁺, all modified sorbents showed approximately equal selectivity for ¹³⁷Cs. Probable applications of the sorbents were suggested.     

Extraction of cesium from water into nitrobenzene using hydrogen dicarbollylcobaltate in the presence of p-nonylphenylnonaethylene glycol

The extraction of cesium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^-) in the presence of Slovafol 909 (p-nonylphenylnonaethylene glycol, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, HL₂ ⁺, CsL⁺ and CsL₂ ⁺ are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Na+ Selective Fluorescent Tools Based on Fluorescence Intensity Enhancements,Lifetime Changes,and on a Ratiometric Response

Over the years, we developed highly selective fluorescent probes for K⁺ in water, which show K⁺-induced fluorescence intensity enhancements, lifetime changes, or a ratiometric behavior at two emission wavelengths (cf. Scheme 1, K1 – K4 ). In this paper, we introduce selective fluorescent probes for Na⁺ in water, which also show Na⁺ induced signal changes, which are analyzed by diverse fluorescence techniques. Initially, we synthesized the fluorescent probes 2 , 4 , 5 , 6 and 10 for a fluorescence analysis by intensity enhancements at one wavelength by varying the Na⁺ responsive ionophore unit and the fluorophore moiety to adjust different K_d values for an intra- or extracellular Na⁺ analysis. Thus, we found that 2 , 4 and 5 are Na⁺ selective fluorescent tools, which are able to measure physiologically important Na⁺ levels at wavelengths higher than 500 nm. Secondly, we developed the fluorescent probes 7 and 8 to analyze precise Na⁺ levels by fluorescence lifetime changes. Herein, only 8 (K_d=106 mm ) is a capable fluorescent tool to measure Na⁺ levels in blood samples by lifetime changes. Finally, the fluorescent probe 9 was designed to show a Na⁺ induced ratiometric fluorescence behavior at two emission wavelengths. As desired, 9 (K_d=78 mm ) showed a ratiometric fluorescence response towards Na⁺ ions and is a suitable tool to measure physiologically relevant Na⁺ levels by the intensity change of two emission wavelengths at 404 nm and 492 nm.     

Extraction of cesium by a nitrobenzene solution of sodium bis-1,2-dicarbollylcobaltate in the presence of 15-crown-5

The extraction of microamounts of cesium by a nitrobenzene solution of sodium bis-1,2-dicarbollylcobaltate (Na⁺B⁻) in the presence of 15-crown-5 (15C5, L) has been investigated. The equilibrium data have been explained assuming the complexes NaL⁺, NaL₂ ⁺, CsL⁺ and CsL₂ ⁺ to be extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Tailoring the surface chemistry of carbon fiber and E‐glass composites for improved adhesion

The main challenges in the manufacture of composite materials are low surface energy and the presence of silicon‐containing contaminants, both of which greatly reduce surface adhesive strength. In this study, carbon fiber (CF) and E‐glass epoxy resin composites were surface treated with the Accelerated Thermo‐molecular adhesion Process (ATmaP). ATmaP is a multiaction surface treatment process where tailored nitrogen and oxygen functionalities are generated on the surface of the sample through the vaporization and atomization of n‐methylpyrrolidone solution, injected via specially designed flame‐treatment equipment. The treated surfaces of the polymer composites were analyzed using XPS, time of flight secondary ion mass spectrometry (ToF‐SIMS), contact angle (CA) analysis and direct adhesion measurements. ATmaP treatment increased the surface concentration of polar functional groups while reducing surface contamination, resulting in increased adhesion strength. XPS and ToF‐SIMS showed a significant decrease in silicon‐containing species on the surface after ATmaP treatment. E‐glass composite showed higher adhesion strength than CF composite, correlating with higher surface energy, higher concentrations of nitrogen and C?O functional groups (from XPS) and higher concentrations of oxygen and nitrogen‐containing functional groups (particularly C₂H₃O⁺ and C₂H₅NO⁺ molecular ions, from ToF‐SIMS). Copyright © 2010 John Wiley & Sons, Ltd.     

Characterization of a capillary dielectric barrier plasma jet for use as a soft ionization source by optical emission and ion mobility spectrometry

This paper presents the characterization of a source for soft ionization of organic molecules. This source is based on a plasma jet established at the end of a capillary dielectric barrier discharge at atmospheric pressure. He, Ne and Ar as pure gas or with different concentrations of N₂ are used as buffer gas for the plasma jet. Spectroscopic emission measurements are carried out along the plasma jet in and outside the capillary. The intensity variation of N₂⁺ lines, for example emission at 391.4 and 427.8 nm, can be associated with the protonation process which is the basis for the soft ionization. The mechanism of the N₂⁺ production outside the capillary, which is relevant for the protonation of molecules and sustains the production of primary ions, is investigated. The response signal of the ions in a nitrogen atmosphere was measured with an ion mobility spectrometer (IMS).