In assisted realization of p-type C-doped ZnO: A first-principles study

C mono-doped and C–In co-doped ZnO are investigated by the first-principles calculations. It is found that the C mono-doped ZnO is p-type with hole carriers locating nearby valence band maximum. Furthermore, a shallower C acceptor energy level appears in the band gap after incorporating In into C-doped ZnO system. Meantime, compared with C mono-doped ZnO, C–In co-doped ZnO has a lower formation energy, correspondingly a higher chemical stability, and thus to enhance the incorporation efficiency of C. These results suggest that C–In co-doping method provided an efficient technique for realizing p-type ZnO.     

Simultaneous determination of natural and synthetic estrogens by EKC using a novel microemulsion

A novel microemulsion based on sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was developed for the simultaneous determination of natural and synthetic estrogens by microemulsion EKC (MEEKC). The microemulsion system consisted of 1.4% w/w AOT, 1.0% w/w octane, 7.0% w/w 1-butanol and 90.6% w/w 20 mM sodium salt of 3-(cyclohexylamino)-2-hydroxy-1-propanesulfonic acid (CAPSO) and 10 mM phosphate buffer at pH 12.5. A baseline resolution in the separation of estrone, 17beta-estradiol, estriol, estradiol 17-hemisuccinate, etinilestradiol, estradiol 3-benzoate, and estradiol 17-valerate was achieved in comparison to the traditional MEEKC system with SDS in less than 15 min. The optimized electrophoretic conditions included the use of an uncoated-silica capillary of 60 cm of total length and 75 microm id, an applied voltage of 25 kV, a temperature of 25 degrees C and 214 UV-detection. Parameters of validation such as specificity, linearity, accuracy, LOD, LOQ and robustness were evaluated according to international guidelines. Due to its simplicity, accuracy, and reliability, the proposed method can be an advantageous alternative to the traditional methodologies for the analysis of natural and synthetic estrogens in different pharmaceutical forms.     

Statistical mechanics of bilayer membranes in troubled aqueous media

We consider a bilayer membrane surrounded by small impurities, assumed to be attractive or repulsive. The purpose is a quantitative study of the effects of these impurities on the statistical properties of the supported membrane. Using the replica trick combined with a variational method, we compute the membrane mean-roughness and the height correlation function for almost-flat membranes, as functions of the primitive elastic constants of the membrane and some parameter that is proportional to the volume fraction of impurities and their interaction strength. As results, the attractive impurities increase the shape fluctuations due to the membrane undulations, while repulsive ones suppress these fluctuations. Second, we compute the equilibrium diameter of (spherical) vesicles surrounded by small random particles starting from the curvature equation. Third, the study is extended to a lamellar phase composed of two parallel fluid membranes, which are separated by a finite distance. This lamellar phase undergoes an unbinding transition. We demonstrate that the attractive impurities increase the unbinding critical temperature, while repulsive ones decrease this temperature. Finally, we say that the presence of small impurities in an aqueous medium may be a mechanism to suppress or to produce an unbinding transition, even the temperature and polarizability of the aqueous medium are fixed, in lamellar phases formed by parallel lipid bilayers.     

杂质对KDP晶体光学质量的影响

 研究了几类可能出现在KDP晶体的生长溶液中的有机物杂质和无机阴离子杂质基团对KDP晶体散射、透过率、光损伤阈值等光学质量的影响，结果表明，不同种类的杂质的影响并不相同，造成这一结果的根本原因在于杂质离子的结构及其与晶体表面原子成键能力的不同。     

Isolation and identification of two unknown impurities from the raw material of clindamycin hydrochloride

Clindamycin hydrochloride belongs to the antibiotic family of lincomycin. It has the same antibacterial spectrum as lincomycin, but the antibacterial activity is four to eight times stronger than that of lincomycin. There have been some adverse reactions in clinical use of clindamycin hydrochloride and its finished drug products. The impurities in drugs are directly related to their safety. In this study, two unknown impurities were isolated from the raw material of clindamycin hydrochloride through various chromatographic methods. Their structures were identified as clindamycin isomer (impurity 1) and dehydroclindamycin (impurity 2) by mass spectrometry and NMR spectroscopy. Both of them were found for the first time. The two impurities exhibit a similar but lower antibacterial activity compared with clindamycin hydrochloride.     

QbD-mediated RP-UPLC method development invoking an FMEA-based risk assessment to estimate nintedanib degradation products and their pathways

QbD is considered an important, fundamental, and integral part of dosage form development. Despite its significance in drug formulations, the knowledge, reference, and guidance for using QbD in analytical science have not been thoroughly documented in the literature. The present study is aimed at bridging the gap between its generated data and the unexplored terrain in formulation science. This study is novel because, for the first time, an exclusive shorter run time UHPLC method for estimating degradation products was developed through the QbD approach, validated, and proved stability indicative. Five degradation impurities were separated and well characterized. Further, the degradation pathway of the anticancer drug nintedanib (NIN) was explored for the first time in the soft gel formulation using tandem quadrupole MS abetted mass identification, and ESI/MS/MS aided structure elucidation was performed. By carefully demonstrating the step-by-step procedure for QbD-based optimization, parameters such as the analytical target profile (ATP) and critical quality attributes (CQAs) were assessed. The risk assessment was performed using failure mode effect analysis (FMEA). Critical method attributes and critical method parameters were identified based on the magnitude of the calculated risk priority number (RPN) value. Designed experiments using 4-factor two-level factorial design monitored three critical quality attributes to arrive at a method operable design space (MODS). The effect of individual method attributes was also analyzed using half-normal and Pareto charts. Control strategies design and RPN values were recalculated based on the DOE output. This RPN value is eventually identified to be significantly smaller and satisfactory within the allowable limit.     

电感耦合等离子体质谱法测定高纯氧化钕中稀土杂质的研究

本文报导了高纯氧化钕中Ｙ、Ｌａ、Ｃｅ、Ｐｒ、Ｓｍ、Ｅｕ、Ｇｄ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ等１１中稀土杂质的电感耦合等离子体质谱测定方法。选择了仪器最佳操作参数，研究了质谱干扰和基体效应，采用Ｔ１内标可基本克服基体效应。方法检出限为０．０１９－０．０９５ｎｇ／ｍＬ，加标回收率为８１．８％－１０３．３％。     

Influence of polyethylenimine on the precipitation process of lead sulfate crystals

Crystals of lead sulfate were precipitated in a solution of polyethylenimine (PEI) using a double-jet crystallizer. PEI controlled both the nucleation rate and the growth rate, and enabled to produce fine monodispersed crystals. This effect is considered to be due to a complexation between PEI and lead ion. The on-line measurement of the variation in the lead ion concentration indicated PEI lost its effect when a certain amount of reactants was supplied. And the duration in which PEI could control the precipitation rate and the amount of PEI had a strong correlation. In addition, it was suggested that their relationship could be utilized in order to produce monodispersed particles.     

Interactive effect of impurities on giant magnetoresistance of Co–Fe/Cu multilayers

Giant magnetoresistance of Co–Fe–B/Cu multilayers fabricated in the sputtering atmosphere, where the amount of oxygen impurity is varied, is discussed in connection with their interfacial roughness. The magnetoresistance (MR) ratio of Co–Fe/Cu multilayers is enhanced by up to 33% when the oxygen content is varied between 10 and 100 ppm of processing Ar gas. The enhancement of the MR ratio was due to the flattening effect of impurity oxygen on the multilayer interfaces: the root mean square roughness of the multilayer was decreased from 7.5 to 5 Å. With increasing boron content in Co–Fe layers, however, the enhancing effect of MR ratio by oxygen diminished and nearly vanished for 12 at%-B–(Co–Fe) case. The strong affinity of boron for oxygen is suggested as a probable mechanism.     

Development of a capillary electrophoresis method for the assay of ramipril and its impurities: an issue of cis-trans isomerization

The development of a rapid and selective capillary electrophoresis method for the quantitation of ramipril and its eight main impurities in pharmaceutical dosage form is described. Ramipril and three of its impurities contain a proline-similar moiety which causes in solution the presence of interconverting cis-trans isomers with respect to the amide bond. The interplay between electrophoretic migration and isomerization may yield the presence of an undesired interconversion zone between the two isomer peaks in the electropherogram, depending on the experimental conditions. Different capillary electrophoresis operative modes and pseudostationary phases were evaluated, both in normal and reverse polarity, in order to find the essential analytical parameters which could make it possible to overcome this issue and thus accurately quantify the analytes. The best results were obtained by using microemulsion electrokinetic chromatography in reverse polarity, where all the compounds which undergo cis-trans interconversion migrate as a single narrow peak. Experimental design led to identification of the following optimised conditions: background electrolyte, microemulsion made by 88.95% of 90 mM phosphate pH 2.5, 1.05% of n-heptane and 10.00% of SDS/n-butanol in 1:2 ratio; voltage, -26 kV; temperature, 17°C. Applying these conditions, the baseline separation of the analytes was obtained in about 10 min. Validation of the method following ICH guidelines was carried out and the procedure was applied to a real sample of ramipril tablets.