Spectrophotometric determination of channel black in small arms propellants

A spectrophotometric method is proposed for the determination of Channel Black in small arms propellants. The Channel Black is separated from the nitrocellulose and other organic compounds by dissolution of the propellant in morpholine and filtration through a sintered porcelain crucible containing an asbestos mat. The Channel Black is then dissolved by treating the mat and crucible with boiling nitric acid for 3 hr, the solution is filtered, and the yellow colour is measured. The colour is due to polycarboxylic acids with cyclic nuclei. The range of the method is from 0 to 0.5% of Channel Black.     

Method development and validation study for quantitative determination of nifedipine and related substances by ultra‐high‐performance liquid chromatography

A novel stability‐indicating reversed phase ultra‐high performance liquid chromatography (UPLC) coupled photodiode array gradient method was developed for determination of the nifedipine and related compounds. Furthermore, based on the chromatographic conditions and forced degradation studies performed through the development of the related substances method a UPLC isocratic method was validated for the determination of the assay of this active substance. An Acquity Shield RP₁₈ (50 × 3.0 mm 1.7 µm) column was used for separation of nifedipine and its five potential impurities within 11 min, which is 5‐fold less than the official method. A mobile phase consisting of 10 mm ammonium formate (pH 4.5) and methanol, delivered at a flow rate 0.5 mL/min, was employed to achieve a minimum resolution of 2.0 for all consecutive pairs of compounds. The precision value expressed as percentage relative standard deviation for method repeatability and reproducibility was <5.0%. The recoveries for all the related compounds were in the range of 99–105.0%. Linearity was found to be acceptable over the concentration range of 0.25–1.5 µg/mL for nifedipine and its impurities. The limit of quantification for nifedipine was 0.05 µg/mL, which is much less than the European Pharmacopoeia method. Copyright © 2014 John Wiley & Sons, Ltd.     

A 3,4‐trans‐Fused Cyclic Protecting Group Facilitates α‐Selective Catalytic Synthesis of 2‐Deoxyglycosides

A practical approach has been developed to convert glucals and rhamnals into disaccharides or glycoconjugates with high α‐selectivity and yields (77–97 %) using a trans‐fused cyclic 3,4‐O‐disiloxane protecting group and TsOH?H₂O (1 mol %) as a catalyst. Control of the anomeric selectivity arises from conformational locking of the intermediate oxacarbenium cation. Glucals outperform rhamnals because the C6 side‐chain conformation augments the selectivity.     

电感耦合等离子体原子发射光谱法测定钛酸钡纳米粉体中7种杂质元素

钛酸钡纳米粉体样品用盐酸溶解,在所得样品溶液中用电感耦合等离子体原子发射光谱法测定了以氧化物存在于样品中的7种杂质元素(包括镁、锶、钾、钠、铝、硅及铁),对测定的光谱条件进行了试验并优化达到上述各元素的测定上限为0.1%(质量分数).测得方法的检出限(3S/b)为(单位μg·L-1):2.0(铝),1.0(铁),20.0(钾),0.2(镁),4.0(钠),3.0(硅)及0.5(锶).应用此方法分析了两件实样,所得结果的相对标准偏差(n=6)小于等于2.0%,对其中4种杂质元素(镁、钾、钠和锶)同时用HG/T 3587-1999标准中的方法作分析校核,所得结果与此方法结果一致.     

Lanthanoid coordination with a tetrazole-substituted calix[4]diquinone and calix[4]dihydroquinone

The tetrazole-functionalised calixdiquinone 5,17-di-tert-butyl-26,28-bis-(1H-tetrazole-5-ylmethoxy)-calix[4]-25,27-diquinone Q was synthesised by chemical oxidation of the bis-tetrazole calix[4]arene precursor using PbO₂/HClO₄. The single crystal X-ray structure determination of Q confirmed the structure and showed binding of a water molecule in the solid state. Chemical reduction of Q to the dihydroquinone QR was achieved using N,N-diethylhydroxylamine. Comparison of the solution phase photophysical properties of Q or QR in the presence of terbium ions showed significant excitation only with QR, suggesting redox switching of the photophysical response may be possible with this or similar receptor.     

Electrocatalytic oxidation of formate by [Ni(P(R)2N(R')2)2(CH3CN)]2+ complexes

[Ni(P(R)(2)N(R')(2))(2)(CH(3)CN)](2+) complexes with R = Ph, R' = 4-MeOPh or R = Cy, R' = Ph , and a mixed-ligand [Ni(P(R)(2)N(R')(2))(P(R'(2))N(R'(2)))(CH(3)CN)](2+) with R = Cy, R' = Ph, R' = Ph, have been synthesized and characterized by single-crystal X-ray crystallography. These and previously reported complexes are shown to be electrocatalysts for the oxidation of formate in solution to produce CO(2), protons, and electrons, with rates that are first-order in catalyst and formate at formate concentrations below ～0.04 M (34 equiv). At concentrations above ～0.06 M formate (52 equiv), catalytic rates become nearly independent of formate concentration. For the catalysts studied, maximum observed turnover frequencies vary from <1.1 to 15.8 s(-1) at room temperature, which are the highest rates yet reported for formate oxidation by homogeneous catalysts. These catalysts are the only base-metal electrocatalysts as well as the only homogeneous electrocatalysts reported to date for the oxidation of formate. An acetate complex demonstrating an η(1)-OC(O)CH(3) binding mode to nickel has also been synthesized and characterized by single-crystal X-ray crystallography. Based on this structure and the electrochemical and spectroscopic data, a mechanistic scheme for electrocatalytic formate oxidation is proposed which involves formate binding followed by a rate-limiting proton and two-electron transfer step accompanied by CO(2) liberation. The pendant amines have been demonstrated to be essential for electrocatalysis, as no activity toward formate oxidation was observed for the similar [Ni(depe)(2)](2+) (depe = 1,2-bis(diethylphosphino)ethane) complex.     

A simple procedure for the rapid optimization of reversed-phase separations with ternary mobile phase mixtures

Summary A simple rapid procedure is described for estimating optimum compositions of ternary mobile phase mixtures for the separation of samples by reversed-phase liquid chromatography (RPLC). Retention data in two iso-eluotropic binary mobile phase mixtures (mixtures with equal retention times) are required to initiate the procedure. The logarithm of the capacity factor is assumed to vary linearly with the composition of isoeluotropic ternary mixtures formed by mixing the two limiting binaries. Using the product of resolution factors of adjacent peaks as the criterion, an optimum ternary composition is then calculated. After a chromatogram has been obtained with the predicted optimum ternary mobile phase, the procedure is repeated until no further improvement can be achieved. Examples of the application of the present procedure are described to illustrate its effectiveness.