Relating glass formation to eutectic composition in Cu100-xZrx alloy by molecular dynamics simulation

The relationship between eutectic compositions and glass-forming ability (GFA) in Cu_100-xZr_x (x = 8–83) system is studied by molecular dynamic (MD) simulation based on the embedded atom method (EAM). Local maxima of GFA occur in Cu₅₆Zr₄₄, Cu₄₇Zr₅₃ and Cu₃₁Zr₆₉ alloys, close to eutectic points in Cu-Zr binary phase diagram. The structural parameters indicate that the heterogeneous Cu-Zr pairs exhibit stronger and more stable interaction than that of homogeneous pairs. The small peak with a negative amplitude ahead of the main peak in S_CuZr(Q) also implies the preference of Cu-Zr pairs. The avoidance of Cu-Cu neighbours and Zr-Zr neighbours, which correspond to the prepeak prior to the main peak of S_CuCu(Q) and S_ZrZr(Q), leads to structural order on intermediate length scales. Perfect and defect icosahedra constitute medium range order (MRO) clusters by sharing atoms, which promotes the glass formation.     

Detection of 22 antiepileptic drugs by ultra-performance liquid chromatography coupled with tandem mass spectrometry applicable to routine therapeutic drug monitoring

The purpose of this study was to develop an ultra‐performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) method of 22 antiepileptics for routine therapeutic monitoring. The antiepileptics used in the analyses were carbamazepine, carbamazepine‐10,11‐epoxide, clobazam, N‐desmethylclobazam, clonazepam, diazepam, N‐desmethyldiazepam, ethosuximide, felbamate, gabapentin, lamotrigine, levetiracetam, N‐desmethylmesuximide, nitrazepam, phenobarbital, phenytoin, primidone, tiagabine, topiramate, valproic acid, vigabatrin and zonisamide. After protein precipitation of 50 μL plasma with methanol, the supernatant was diluted with water or was evaporated to dryness and reconstituted with mobile phase in the case of benzodiazepines. Separation was achieved on an Acquity UPLC BEH C₁₈ column with a gradient mobile phase of 10 mm ammonium acetate containing 0.1% formic acid and methanol at a flow rate of 0.4 mL/min. An Acquity TQD instrument in multiple reaction monitoring mode with ion mode switching was used for detection. All antiepileptics were detected and quantified within 10 min, with no endogenous interference. All the calibration curves showed good linearity in the therapeutic range (r² < 0.99). The precision and accuracy values for intra‐ and inter‐assays were within ±15% except for phenobarbital and tiagabine. A good correlation was observed between the concentration of clinical samples measured by the new method described here and the conventional methods. The values of carbamazepine and phenytoin by UPLC‐MS/MS were lower than those detected by the immunoassays, which might be caused by the cross‐reaction of antibodies with their metabolites. In conclusion, we developed a simple and selective UPLC‐MS/MS method suitable for routine therapeutic monitoring of antiepileptics. Copyright © 2012 John Wiley & Sons, Ltd.     

HCl处理后局部有序Y沸石的二次晶化

将商品 Y 型沸石用 HCl 处理后, 运用 X 射线粉末衍射, 透射电镜和扫描电镜、红外光谱及 27Al 和 29Si 魔角旋转核磁共振对其进行了表征. 结果表明, 酸处理后 Y 沸石接近无定形, 其长程有序性遭到破坏, 但还保留部分局部结构. 以不同浓度酸处理后的 Y 沸石为前驱体, 在 150 oC, 0.3 mol/L NaOH 条件下采用蒸汽辅助干胶转化法进行二次晶化, 可以获得丝光沸石, 其相纯度与前驱体的 Si/Al 密切相关. 随 Si/Al 比不同, 所得丝光沸石形貌由纳米针状堆积逐渐向微米单块状变化, 且其比表面积可达 400 m2/g 以上, 微孔孔容在 0.19 cm3/g.     

Development of a candidate certified reference material of cypermethrin in green tea

This paper presents the preparation of a candidate certified reference material (CRM) of cypermethrin in green tea, GLHK-11-01a according to the requirements of ISO Guide 34 and 35. Certification of the material was performed using a newly developed isotope dilution mass spectrometry (IDMS) approach, with gas chromatography high resolution mass spectrometry (GC–HRMS) and gas chromatography–tandem mass spectrometry (GC–MS/MS). Statistical analysis (one-way ANOVA) showed excellent agreement of the analytical data sets generated from the two mass spectrometric detections. The characterization methods have also been satisfactorily applied in an Asia-Pacific Metrology Program (APMP) interlaboratory comparison study. Both the GC–HRIDMS and GC–IDMS/MS methods proved to be sufficiently reliable and accurate for certification purpose. The certified value of cypermethrin in dry mass fraction was 148 μg kg⁻¹ and the associated expanded uncertainty was 14 μg kg⁻¹. The uncertainty budget was evaluated from sample in homogeneity, long-term and short-term stability and variability in the characterization procedure. GLHK-11-01a is primarily developed to support the local and wider testing community on need basis in quality assurance work and in seeking accreditation.     

Chlorodesmethyldiazepam Fluorimetric Determination in Pharmaceutical Formulations and in Aqueous Media

Abstract

A direct fluorimetric method for the determination of chlorodesmethyldiazepam was proposed. The fluorescence process was pH dependent. The dynamic range for the method was 1.6–12 µg ml^–1. A linear relationship between the fluorescence intensity and the concentration of chlorodesmethyldiazepam solution was obtained with r ² of 0.9958. The detection limit for the method was found to be 0.224 µg ml^–1. The method has successfully applied to the determination of chlorodesmethyldiazepam in pure, authentic, and aqueous samples.     

Characterization of Geological Certified Reference Materials by Inductively Coupled Plasma-Mass Spectrometry

A rapid, safe, and efficient microwave-assisted acid digestion method is reported to determine thirty-six elements in three international geological reference materials and two in-house reference materials using high resolution inductively coupled plasma mass spectrometry. This method was also employed to determine the radiogenic isotopic composition of Sr and Nd in two geological reference materials by multicollector inductively coupled plasma mass spectrometry. In order to ascertain the most suitable preparation method, four microwave-assisted digestion procedures were compared. The presence of insoluble fluorides on the recoveries of Ba, Rb, Sr and rare earth elements was resolved through sequential evaporation at 80 degrees Celsius followed by microwave digestion. Digestion methods without using HClO₄ or H₃BO₃ and using only H₃BO₃ were unsuitable due to lower recoveries and higher procedural blanks, respectively. Digestion methods that involved the use of HCl-HNO₃-HF and HCl-HNO₃-HF-HClO₄ were most suitable, resulting in better recoveries of the elements. However, the HCl-HNO₃-HF method was preferred compared to HCl-HNO₃-HF-HClO₄ because the former avoids the use of HClO₄ and thus was used in measurements of the radiogenic isotopes of Sr and Nd. The optimized method was used to verify the reference values for the isotopic compositions of Sr and Nd in geological standard reference materials.     

透光率计滤光片标准物质的研制

以中性灰玻璃及特种石英玻璃为材料,采用切割、研磨、抛光等工艺,制备了校准透光率计用系列滤光片标准物质,标准物质的均匀性不确定度为0.08%,校准周期内的稳定性不确定度为0.19%,扩展不确定度为0.5%(k=2)。该标准物质可广泛用于校准透光率计,具有携带方便、性能稳定等优点。     

Determination of Trace Elements in Biological Standard Reference Materials by Graphite Furnace Atomic Absorption Spectrometry with Solid and Slurry Sampling

Compared to conventional dissolution methods, solid and slurry sampling methods offer advantages which include speed, improved sensitivity, a reduced risk of contamination, and a reduced risk of analyte loss. Most successful graphite furnace atomic absorption spectrometry (GFAAS) results have been obtained by the use of modern furnace technology, which includes Zeeman background correction, platform atomization, and matrix modifiers. In this work, solid and slurry sampling were investigated for the determination of Ag, Cu, Fe, Mn, Pb, and Zn in biological National Institute of Standards and Technology (NIST) standard reference materials (SRMs) with the use of vintage (1980) GFAAS instrumentation, aqueous calibration, and deuterium arc background correction. Although reasonable accuracy was obtained with solid sampling, the relative standard deviation was between 13 and 53%, which was probably caused by the inability of the furnace to reproducibly vaporize the sample and the inability of deuterium arc background correction to account for the high background signals. Good accuracy and precision (3–13%) were obtained with slurry sampling, with the exception of the determination of copper in citrus leaves. This low result (three times below the certified value) and high precision (RSD = 31%) were probably caused by irreproducible atomization of the sample matrix.     

The contact in the BCS–BEC crossover for finite range interacting ultracold Fermi gases

Using mean-field theory for the Bardeen–Cooper–Schriefer (BCS) to the Bose–Einstein condensate (BEC) crossover we investigate the ground state thermodynamic properties of an interacting homogeneous Fermi gas. The interatomic interactions modelled through a finite range potential allows us to calculate the thermodynamic behaviour as a function of the potential parameters in the whole crossover region. We concentrate in studying the Contact variable, the thermodynamic conjugate of the inverse of the s-wave scattering length. Our analysis leads to predict a quantum phase transition – like in the case of large potential range. This finding is a direct consequence of the k-dependent energy gap.