Single Crystals of NaPrTe2 with LiTiO2‐Type Structure

During attempts to synthesize rare‐earth nitride tellurides black and bead‐shaped single crystals of the title compound sodium praseodymium(III) ditelluride (NaPrTe₂) were obtained as a by‐product by reacting a mixture of praseodymium, sodium azide (NaN₃) and tellurium at 900 °C for seven days in evacuated torch‐sealed silica vessels. NaPrTe₂ crystallizes cubic (space group: Fd3¯m, Z = 16; a = 1285.51(9) pm, V_m = 79.96(1) cm³/mol, R₁ = 0.028 for 146 unique reflections) and exhibits the Na⁺ and Pr³⁺ cations in slightly distorted octahedra of six telluride anions (d(Na—Te) = 325 pm, d(Pr—Te) = 317 pm) each. The main characteristics of this new structure type for alkali‐metal rare‐earth(III) dichalcogenides can be derived from the rock‐salt type structure (NaCl, cubic closest‐packed Te^2— arrangement, all octahedral voids occupied with Na⁺ and Pr³⁺) with alternating layers consisting of Na⁺ and Pr³⁺ cations in a ratio of 3:1 and 1:3, respectively, piled along the [111] direction.     

Micellar electrokinetic capillary chromatography using polymeric hollow fibers

Summary In this paper, polymeric hollow fibers prepared from pH-stable polypropylene were used as columns for micellar electrokinetic capillary chromatography (MECC). The electroosmotic flow (EOF) for polypropylene hollow fibers was evaluated in the pH range of 5.0–12.0. With untreated polypropylene hollow fibers a stabilized but enhanced EOF was achieved when SDS was used in the buffer, decreasing the separation window for uncharged substances in MECC to impractical levels. Uncharged acrylamide and charged 2-acryloylamido-2-methylpropane sulfonic acid surface modifications were used to lower the strength of the EOF, increase the separation window and prevent local overheating that could melt the column wall.     

Unexpected formation of the novel fluorinated diazenes

Fluoroalkanesulfonyl azides reacted with morpholine giving unexpectedly N-fluoroalkanesulfonyl-N-morpholino diazenes, which were fully characterized by using spectral methods and X-ray diffraction analysis.     

Simultaneous determination of trace uranium(VI) and zinc(II) by adsorptive cathodic stripping voltammetry with aluminon ligand

Uranium(VI) complexed with aluminon (3-[bis(3-carboxy-4-hydroxy-phenyl)methylene]-6-oxo-1,4-cyclohexadiene-1-carboxylic acid triammonium salt) was determined by adsorptive cathodic stripping voltammetry (ACSV) using a hanging mercury drop electrode. Trace uranium(VI) and zinc(II) can be simultaneously determined in a single scan in the presence of aluminon and urea. Optimal conditions were found to be: accumulation time; 180–200 s, accumulation potential; 50 mV versus Ag/AgCl, scan rate; 40 mV s⁻¹, supporting electrolyte; 0.1 M sodium acetate buffer at pH 6.5–7.0, and concentration of aluminon; 1×10⁻⁶ M. The linear range of uranium(VI) and zinc(II) were observed over the concentration range 2–33 and 30–120 ng ml⁻¹, respectively. The detection limit (S/N=3) are 0.2 ng ml⁻¹ (uranium) and 30 ng ml⁻¹ (zinc). A good reproducibility shows RSDs of 2.5–4.0% (n=10). The procedure offers high selectivity, with the presence of urea masking some metal ions.     

Trifluoromethylation of carbonyl compounds with sodium trifluoroacetate

In the presence of copper(I) iodide as catalyst, a variety of carbonyl compounds, such as aldehydes, ketones and acid anhydrous, could be trifluoromethylated with sodium trifluoroacetate to give the corresponding alcohols in moderate to high yields, and a possible mechanism was proposed to explain the roles of catalyst and solvent in the reaction system.     

A novel method of the determination of boron in the presence of a little methanol by discoloring spectrophotometry in pharmaceutical and biological samples

It is the first time that boron is determined in the presence of a little methanol by discoloring spectrophotometry in this paper. A russety product can be formed by the reaction between glycine (Gly) and sodium 1,2-naphthoquinone-4-sulfonate (NQS) in alkaline solution. When boron is added to the solution, the system will be discolored, and the addition of a little methanol will improve the discoloration. Beer's law is obeyed in the range of boron concentrations of 0.86-43.24 μg ml⁻¹ at the maximal discoloring wavelength of 382 nm. The equation of linear regression is A = −0.07581-86.79186C (mol l⁻¹), with a linearly correlation coefficient of 0.9979. The detection limit is 0.80 μg ml⁻¹ and R.S.D. is 4.2%. The method is successfully applied to the determination of boron in pharmaceutical and biological samples. The average recoveries are in the range of 98.2-104.1%. Analytical results obtained with this novel method are satisfactory.     

Simultaneous speciation of mercury and butyltin compounds in natural waters and snow by propylation and species-specific isotope dilution mass spectrometry analysis

A robust method has been developed for simultaneous determination of mercury and butyltin compounds in aqueous samples. This method is capable of providing accurate results for analyte concentrations in the picogram per liter to nanogram per liter range. The simultaneous determination of the mercury and tin compounds is achieved by species-specific isotope dilution, derivatization, and gas chromatography–inductively coupled plasma mass spectrometer (GC–ICP–MS). In derivatization by ethylation and propylation, reaction conditions such as pH and the effect of chloride were carefully studied. Ethylation was found to be more sensitive to matrix effects, especially for mercury compounds. Propylation was thus the preferred derivatization method for simultaneous determination of organomercury and organotin compounds in environmental samples. The analytical method is highly accurate and precise, with RSD values of 1 and 3% for analyte concentrations in the picogram per liter to nanogram per liter range. By use of cleaning procedures and SIDMS blank measurements, detection limits in the range 10–60 pg L^–1 were achieved; these are suitable for determination of background levels of these contaminants in environmental samples. This was demonstrated by using the method for analysis of real snow and seawater samples. This work illustrates the great advantage of species-specific isotope dilution for the validation of an analytical speciation method—the possibility of overcoming species transformations and non-quantitative recovery. Analysis time is saved by use of the simultaneous method, because of the use of a single sample-preparation procedure and one analysis.     

Interactions between gelatin and sodium dodecyl sulphate: binding isotherm and solution properties

The interaction between sodium dodecyl sulphate (SDS) and gelatin was studied at pH 4.5 and 6.5 where the gelatin is positively charged (i.e.p. 8). At pH 4.5 a SDS/gelatin concentration range was found where gelatin precipitates. At pH 6.5 the SDS-gelatin complex remains soluble although three SDS concentration domains were distinguished where the SDS-gelatin complex had very different affinities for the solvent. Below C₁ the complex was highly surface active but other measurements (viscosity, potentiometry, protons uptake) did not reveal any particular consequence of binding. Between C₁ and C₂ the molecular size decreased (viscosity lowering) upon charge neutralization and collapse about small SDS aggregates (17 SDS molecules per gelatin molecule). Above C₂ a cooperative binding mechanism lead to the formation of SDS aggregates; the complex stretched out and turned strongly hydrophilic (the viscosity increases, low surface activity). At saturation one gelatin molecule bound about 200 SDS molecules. Above the overlap concentration (about 3 wt%) SDS aggregates formed between several gelatin molecules, the viscosity increased continuously with SDS concentration and the binding ratio was lower than in dilute gelatin solutions. A very good correspondence was found between the different analytical data including turbidity, viscosity, surface tension, protons uptake and direct potentiometric SDS binding measurements.     

重氮树脂与十二烷基硫酸钠相互作用研究

重氮树脂与十二烷基硫酸钠相互作用研究罗杨磊曹维孝（北京大学化学与分子工程学院北京１００８７１）关键词重氮树脂，十二烷基硫酸钠，负性ＰＳ版随着化学与生命科学领域的发展，大分子与小分子在溶液的相互作用越来越受到关注．表面活性剂因其具有自组装能力，...     

SDS胶束对孔雀绿褪色反应的影响

研究了十二烷基硫酸钠（SDS）表而活性剂胶束和预胶束对孔雀绿褪色可逆反应的影响，建立了1－1型可逆反应的胶束催化模型和预胶束催化模型，获得了胶束相中正逆反应的速率常数和预胶束的平均聚集数．结果表明，SDS胶束和预胶束对正反应有禁阻作用，而对逆反应有催化作用．