Impurity effects at hydrophobic surfaces

The effective charge of hydrophobic surfaces and in particular of the air–water interface is a crucial parameter for electrochemistry, colloidal chemistry and interfacial science, but different experiments give conflicting estimates. Zeta-potential and disjoining-pressure measurements point to a strongly negative surface charge, often interpreted as being due to adsorbing hydroxide ions. In contrast, surface tension measurements of acids and bases suggest the hydronium ion to be surface active, in agreement with some surface-specific non-linear spectroscopy results. The air–electrolyte interfacial tension exhibits a characteristic minimum at millimolar electrolyte concentration for all salts, the so-called Jones–Ray effect, which points to competitive adsorption mechanisms present in dilute electrolyte solutions. We show that all these puzzling experimental findings can be explained by the presence of trace amounts of surface-active charged impurities, most likely anionic surfactants.     

Trace Impurity Removal from Air

In addition to Nitrogen, Oxygen and Argon, ambient air contains many trace impurities. These impurities include moisture, Carbon Dioxide, Oxides of Nitrogen and light Hydrocarbons. Prior to cryogenic distillation of air to produce Nitrogen, Oxygen and Argon these trace impurities have to be removed since, some of these constitute a safety hazard in the cryogenic plant. A significant amount of information is available in the literature for the removal of Water and Carbon Dioxide from air. However, only limited information is available for the removal of other trace impurities. We discuss the results of an experimental study on the removal of these trace impurities from air.These days, air pre purification is carried out primarily by adsorption based technologies. There are two main choices: Thermal Swing Adsorption (TSA) processes, and Pressure Swing Adsorption (PSA) processes. Main differences between these two approaches and the trace impurity removal results are discussed.     

Impurity analysis in pure-grade 1,3-butadiene

Summary The separation of 20 impurities in a pure-grade 1,3-butadiene has been carried out at 46°C by using Carbopack B modified with 4.94% picric acid.     

Shell-confined hydrogen atom

Calculations of electronic energy and static dipole polarizability are reported for the hydrogen atom in the ns states (n = 1-6) confined between two impenetrable concentric spheres of inner and outer radii placed at the locations of the radial nodes corresponding to the free hydrogen ns (n = 2-7) orbitals. Interesting new conditions of degeneracy arising due to the shell confinement are discussed. Shell-confined states of unusually high polarizability are predicted for hydrogen atom as the inner sphere radius is shifted towards the outer nodal points of the free atom corresponding to the higher principal quantum numbers.     

Non-Hermitian Hydrogen atom

We have constructed a set of non-Hermitian operators that satisfy the commutation relations of the $SO(3)$ SO ( 3 ) -Lie algebra. Using these set of operators we have constructed a non-Hermitian Hamiltonian corresponding to the Hydrogen atom that includes a complex term but with the same spectra as in the Hermitian case. It is also found a non-Hermitian Runge–Lenz vector that represents a conserved quantity. In this way, we obtain a set of non-Hermitian operators that satisfy the commutation relations of the $SO(4)$ SO ( 4 ) -Lie algebra.     

盐酸多奈哌齐开环杂质的合成

以盐酸多奈哌齐为起始原料,与草酸二乙酯和双氧水经一锅煮法合成了多奈哌齐的开环杂质,纯度98.8%,总收率31.2%,其结构经¹H NMR和MS(ESI)确证。     

Impurity profiling of pharmaceuticals by thin-layer chromatography

Although there is a tendency in current pharmacopoeias for favouring HPLC, thin-layer chromatography (TLC) is still a very popular and frequently used analytical method in the pharmaceutical industry. This paper highlights the possibilities of this method in the different areas of pharmaceutical analysis like in-process and intermediate control, illustrated by impurity testing of active ingredients and final products, as well as its application in pharmaceutical research and development, based on some examples reported mainly in the last five years.     

盐酸苯达莫司汀杂质的合成

以[1-甲基-2-(4′-丁酸乙酯基)-5-氨基]-1H-苯并咪唑为原料,与氯乙醇经-N-单羟乙基化反应制得[1-甲基-2-(4′-丁酸乙酯基)-5-(2′-羟基乙基)氨基]-1H-苯并咪唑(A); A与氯化亚砜经氯化反应制得[1-甲基-2-(4′-丁酸乙酯基)-5-(2′-氯乙基)氨基]-1H-苯并咪唑(B); B在浓盐酸中经水解成盐反应合成了盐酸苯达莫司汀杂质[1-甲基-2-(4′-丁酸基)-5-(2′-氯乙基)氨基]-1H-苯并咪唑盐酸盐,总收率24.5%,纯度98.12%,其结构经¹H NMR, ¹³C NMR和HR-MS(ESI)确证。     

高效液相色谱法测定依托咪酯异构体杂质

建立了依托咪酯异构体杂质的高效液相色谱（HPLC）方法,采用AD-H柱,流速0.8 mL/min,检测波长235 nm.经方法学验证,该方法对依托咪酯及其异构体专属性确认分离度大于2.0,对依托咪酯异构体杂质的最小检测限（LOD）为0.002％,线性范围为0.001 6.μg～0.052 6 μg,相关系数r=0.999 44,加样回收率分别为82.0％、90.5％和96.2％.结果表明该检测方法专属性好,灵敏度高,准确,用于依托咪酯异构体杂质测定结果可靠.     

丹曲林钠杂质B的合成

以5-对硝基苯胺为原料,与糠醛经重氮化反应制得5-对硝基苯基糠醛(1);1与1-氨基乙内酰脲盐酸盐经缩合、精制得丹曲林(2);2与甲醇钠成盐制得丹曲林钠(3);3在氢氧化钠水溶液中加热条件下,经开环水解制得丹曲林钠杂质B钠盐,再经盐酸酸化、精制合成了丹曲林钠杂质B,总收率16.9%,纯度99.9%,其结构经1H NMR,IR和MS(ESI)确证。     

格隆溴铵脱氢杂质的合成

以扁桃酸为起始原料，经环化、缩合、脱水、开环、酯化和甲基化反应合成了格隆溴铵的脱氢杂质--3-[2-(环戊-1-烯-1-基)-2-羟基-2-苯基乙酰氧基]-1,1-二甲基吡咯烷-1-溴化物，总收率50.8%，纯度97.5%，其结构经¹H NMR， ¹³C NMR， IR和元素分析确证。     

Impurity annihilation: chromatography-free parallel Mitsunobu reactions

Mitsunobu reaction of an alcohol ROH with a carboxylic acid, phthalimide, or N-hydroxyphthalimide (NuH) using DNAD (4) and (diphenylphosphino)polystyrene (11) gave the products RNu. Ring-opening metathetic polymerization of the side product DNADH(2) (3) using Cl(2)(Cy(3)P)(2)Ru=CHPh (13) and filtration, to remove poly(DNADH(2)), (diphenylphosphino)polystyrene 11, its oxide, and its adduct with excess DNAD, gave RNu (43-100%, 86-96% purity) without recourse to chromatography.     

利伐沙班关键杂质的合成

以对溴硝基苯为原料,经偶联、胺基保护、亲核取代、硝基还原、环氧开环、环合、脱保护和胺基酰化反应合成了利伐沙班的二胺杂质--5-氯-N-【【(5S)-2-氧代-3-｛4-［5-氯-噻吩-2-甲酸-N-(2-甲基氨基甲酰基甲氧基乙基)酰胺基］苯基｝-1,3-噁唑烷-5-基】甲基】-2-噻吩甲酰胺,其结构经¹H NMR, ¹³C NMR, DEPT135°, ¹H-¹HCOSY, HSQC, HMBC和MS（ESI）确证。     

Hierarchical atom type definitions and extensible all‐atom force fields

The extensibility of force field is a key to solve the missing parameter problem commonly found in force field applications. The extensibility of conventional force fields is traditionally managed in the parameterization procedure, which becomes impractical as the coverage of the force field increases above a threshold. A hierarchical atom‐type definition (HAD) scheme is proposed to make extensible atom type definitions, which ensures that the force field developed based on the definitions are extensible. To demonstrate how HAD works and to prepare a foundation for future developments, two general force fields based on AMBER and DFF functional forms are parameterized for common organic molecules. The force field parameters are derived from the same set of quantum mechanical data and experimental liquid data using an automated parameterization tool, and validated by calculating molecular and liquid properties. The hydration free energies are calculated successfully by introducing a polarization scaling factor to the dispersion term between the solvent and solute molecules. © 2015 Wiley Periodicals, Inc.     

Metal atom oxidation lasers

Stimulated emission in the infrared was observed when fine wires, metallic films and graphite smears were exploded into oxidizing gases. Laser action was attributed to the following diatomic molecules: LiF, CF, CO, MgF, TiF, TiO, FeF, NiF, CuF, PtF, AuF, UF, and UO.     

达格列净呋喃环杂质的合成

以5-溴-2-氯-4′-乙氧基二苯甲烷为原料，与2,3-二-O-叔丁基二甲基硅基-5,6-O-异亚丙基-D-葡糖醛酸-1,4-内酯缩合后，再经还原、脱保护、酯化及水解反应合成了达格列净呋喃环杂质--(1S)-1,4-脱水-1-(4-氯-3-(4-乙氧基苄基)苯基)-D-葡萄糖，总收率29.0%，纯度98.5%，其结构经¹H NMR，¹³C NMR， DEPT135，¹H-¹H COSY， HSQC， HMBC和MS(ESI)确证。