NMR Crystallography Reveals Carbonate Induced Al-Ordering in ZnAl Layered Double Hydroxide

Layered double hydroxides (LDHs) serve a score of applications in catalysis, drug delivery, and environmental remediation. Smarter crystallography, combining X-ray diffraction and NMR spectroscopy revealed how interplay between carbonate and pH determines the LDH structure and Al ordering in ZnAl LDH. Carbonate intercalated ZnAl LDHs were synthesized at different pH (pH 8.5, pH 10.0, pH 12.5) with a Zn/Al ratio of 2, without subsequent hydrothermal treatment to avoid extensive recrystallisation. In ideal configuration, all Al cations should be part of the LDH and be coordinated with 6 Zn atoms, but NMR revealed two different Al local environments were present in all samples in a ratio dependent on synthesis pH. NMR-crystallography, integrating NMR spectroscopy and X-ray diffraction, succeeded to identify them as Al residing in the highly ordered crystalline phase, next to Al in disordered material. With increasing synthesis pH, crystallinity increased, and the side phase fraction decreased. Using ¹H−¹³C, ¹³C−²⁷Al HETCOR NMR in combination with ²⁷Al MQMAS, ²⁷Al-DQ-SQ measurements and Rietveld refinement on high-resolution PXRD data, the extreme anion exchange selectivity of these LDHs for CO₃²⁻ over HCO₃⁻ was linked to strict Al and CO₃²⁻ordering in the crystalline LDH. Even upon equilibration of the LDH in pure NaHCO₃ solutions, only CO₃²⁻ was adsorbed by the LDH. This reveals the structure directing role of bivalent cations such as CO₃²⁻ during crystallization of [M²⁺₄M³⁺₂(OH)₂]²⁺[A²⁻]₁⋅yH₂O LDH phases.     

高效阴离子交换色谱-脉冲安培检测法测定烤烟中的水溶性葡萄糖、果糖和蔗糖

用高效阴离子交换色谱-脉冲安培检测法（HPAEC-PAD）测定了烤烟中的水溶性葡萄糖、果糖和蔗糖。采用水浸取及膜过滤法处理烤烟样品,以Dionex CarboPac PA-1阴离子交换柱为色谱柱,0.2 mol/L NaOH水溶液为淋洗液进行分离测定。葡萄糖、果糖和蔗糖的含量与其峰面积的线性关系良好,回收率均在97%以上。方法简便易行,灵敏度高,重现性良好,可以实现对烟草中单糖的快速分离和测定。     

离子交换色谱-积分脉冲安培检测法测定食品中糖

采用离子交换色谱-积分脉冲安培检测法分离测定了鸡精、酱油、沙拉中的葡萄糖、果糖、蔗糖、乳糖和麦芽糖,研究了5种糖在阴离子交换色谱中的保留行为。采用水和0.2 mol.L-1氢氧化钠为淋洗液梯度洗脱,流速为0.5 mL.min-1,CarboPacTMPA 10为分离柱,金电极为工作电极,Ag/AgCl电极为参比电极,积分脉冲安培检测法一次进样测定鸡精、酱油、沙拉中的5种糖的含量。各组分在测试条件下分离效果较好。5种糖类在0.5~10.0 mg.L-1质量浓度范围内与其峰面积呈线性关系。5种糖的检出限(3S/N)为0.8~2.5μg.L-1,该方法用于食品中糖类的测定,5种糖的回收率为91.1%~104.5%。     

Development of Poly(Vinyl Alcohol)-Based Polymers as Proton Exchange Membranes and Challenges in Fuel Cell Application: A Review

Abstract

Poly(vinyl alcohol) (PVA) is a biodegradable, water-soluble membrane that has low methanol permeation and reactive chemical functionalities. Modification of these features makes PVA an attractive proton exchange membrane (PEM) alternative to Nafion^TM. However, the pristine PVA membrane is a poorer proton conductor than the Nafion^TM membrane due to the absence of negatively charged ions. Hence, modification of PVA matrixes whilst complying with the requirements of projected applications has been examined extensively. Generally, three modification methods of PVA membranes have been highlighted in previous reports, and these are (1) grafting copolymerization, (2) physical and chemical crosslinking, and (3) blending of polymers. The use of each modification method in different applications is reviewed in this study. Although the three modification methods can improve PVA membranes, the mixed method of modification provides another attractive approach. This review covers recent studies on PVA-based PEM in different fuel cell applications, including (1) proton-exchange membrane fuel cells and (2) direct-methanol fuel cells. The challenges involved in the use of PVA-based PEM are also presented, and several approaches are proposed for further study.     

采用隔离池的毛细管电泳-间接紫外吸收法测定茶叶中的氨基酸

改进的毛细管电泳-间接紫外吸收法采用了自制隔离池,以对氨基苯甲酸(PAB)为背景电解质,对茶叶中的氨基酸进行了测定。PAB能够提高分离效率,降低检出限。隔离池的使用避免了PAB的电极反应,降低了基线噪声,维持了两缓冲液池间的电流导通。研究了背景电解质的浓度、pH值以及电渗流改性剂的种类和浓度对氨基酸分离的影响。在优化的实验条件下,16种氨基酸在14 min内达到了基线分离,峰面积的相对标准偏差小于5%(n=5),检出限为1.7~4.5 μmol/L,回收率为83.0%~106%。该法快速、便捷和灵敏,已成功应用于茶叶中11种游离氨基酸的检测。     

阴离子交换-积分脉冲安培检测法分离测定氨基酸注射液中的氨基酸和葡萄糖

 用阴离子交换 积分脉冲安培检测法测定了氨基酸注射液中 1 7种氨基酸和葡萄糖。研究了氨基酸和葡萄糖在阴离子交换中的保留行为。采用了优化的水、NaOH和NaAc三元梯度淋洗条件。在优化的梯度淋洗条件和积分脉冲安培检测条件下 ,氨基酸和葡萄糖的检出限为 0 3pmol～ 1 0 3pmol,线性范围约为 2个数量级。样品加标回收率为 88 3 %～ 1 0 4 6 %。方法简单、灵敏、准确。     

Investigation of the Variation of Unit Cell Dimensions of Crystalline Polymers with High‐Resolution FT‐IR Spectroscopy

Summary: High‐resolution FT‐IR spectroscopy has been used for the first time to characterize the variation of the unit cell dimensions of high‐density polyethylene (HDPE). In combination with the unit cell parameters of HDPE measured at different temperatures by Swan using wide‐angle X‐ray diffraction, the relationship between the rocking band shift (730 cm⁻¹) and the change of the unit cell volume of HDPE has been established.

High‐resolution variable‐temperature FT‐IR spectra of HDPE rocking bands with decreasing temperature.     

Determination of rice type by 1H NMR spectroscopy in combination with different chemometric tools

A 400‐MHz ¹H nuclear magnetic resonance (NMR) spectroscopy and multivariate data analysis were used in the context of food surveillance to discriminate 46 authentic rice samples according to type. It was found that the optimal sample preparation consists of preparing aqueous rice extracts at pH 1.9. For the first time, the chemometric method independent component analysis (ICA) was applied to differentiate clusters of rice from the same type (Basmati, non‐Basmati long‐grain rice, and round‐grain rice) and, to a certain extent, their geographical origin. ICA was found to be superior to classical principal component analysis (PCA) regarding the verification of rice authenticity. The chemical shifts of the principal saccharides and acetic acid were found to be mostly responsible for the observed clustering. Among classification methods (linear discriminant analysis, factorial discriminant analysis, partial least squares discriminant analysis (PLS‐DA), soft independent modeling of class analogy, and ICA), PLS‐DA and ICA gave the best values of specificity (0.96 for both methods) and sensitivity (0.94 for PLS‐DA and 1.0 for ICA). Hence, NMR spectroscopy combined with chemometrics could be used as a screening method in the official control of rice samples. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis,characterization and in vitro cytotoxicity of palladium(II) complexes with mixed ligands. X‐ray diffraction study of C31H36ClNPPdS2

Pd(II) complexes with organophosphines and dithiocarbamates derivatives of α‐amino acids were synthesized by reacting N,N‐dicyclohexyldithiocarbamate (DCHDTC, compounds 1 – 3 ) and N‐methylcyclohexyldithiocarbamate (MCHDTC, compounds 4 – 6 ) with (R₃P)₂PdCl₂ (R = Ph, o‐tolyl, Ph₂Cl) in a 1:1 molar ratio. The complexes were characterized by elemental analyses, FT‐IR, multinuclear (¹H, ¹³C and ³¹P) NMR and single X‐ray crystallography, showing that the dithiocarbamate acts as a bidentate ligand and binds to Pd(II) via two sulfur atoms, resulting in a square planar geometry around Pd(II). The cytotoxicity of compounds 2, 3 and 4 was determined in vitro against six human tumour cell lines, MCF7, EVSA‐T, WIDR, IGROV, M19 MEL, A498 and H226. Compounds 3 and 4 showed a moderate to low cytotoxicity, whereas compound 2 exhibited a very low cytotoxicity. The results of antifungal assays showed that compounds 1 – 6 possess antifungal activity against Fusarium moniliformes, Fusarium saolani, Mucor sp., Aspergillus niger and Aspergillus fumigatus. The anti‐inflammatory screening results of 1–6 are quite similar to those observed for the standard drug Declofenac at 10 mg kg^?1, which inhibited the odema by 74% after 4 h. Copyright © 2007 John Wiley & Sons, Ltd.     

毛细管电泳-激光诱导荧光法测定人血浆中的富马酸比索洛尔

建立了毛细管电泳-激光诱导荧光检测(CE-LIFD)技术测定人血浆中富马酸比索洛尔含量的新方法。选用荧光素异硫氰酸酯(FITC)为衍生化试剂,当缓冲溶液为25mmol/LNa2B4O7(pH9.2)、分离电压25kV、柱温20℃、电动进样(10kV×8s)、以峰面积内标法定量、于激发波长/发射波长=488/520nm柱上检测时,富马酸比索洛尔得到较好分离。在选定的电泳条件下,对其线性范围(20～1000μg/L)、检出限(10μg/L)、重现性(日内和日间精密度分别小于4.44%和5.59%)和回收率(96.19%～101.80%)进行了测定。结果表明:迁移时间的重现性<1.58%;峰面积之比的重现性<6%。     

核磁共振研究二茂铁硒铂配合物构象交换热焓

The intramolecular conformational exchange thermodynamics of cis-PtCl[1,1'bis(undecenylseleno)ferrocene](B11SeFcPt) in CDCl3 solution was studied by one dimensional proton NMR． The chemical equilibrium constants were obtained directly from the integration of the 1H NMR spectra and the enthalpy as a function of temperature for the conformational exchange of B11SeFcPt was calculated from the equilibrium constant.     

2H NMR characterization of phenylene ring flip motion in poly(p-phenylene vinylene) films

Solid-state ²H quadrupole echo nuclear magnetic resonance (NMR) spectra and measurements of ²H spin lattice relaxation times have been obtained for films of poly(p-phenylene vinylene) deuterated in phenylene ring positions (PPV-d₄). NMR line shapes show that all the phenylene rings of PPV undergo 180° rotational jumps about the 1,4 ring axis (“ring flips”) at 225°C. The temperature dependence of the ²H line shapes show that the jump motion is thermally activated, with a median activation energy, E_a = 15 kcal/mol, and a distribution of activation energies of less than ±2 kcal/mol. The jump rate was also determined from the magnitude of the anisotropic T₂ relaxation associated with ²H line shapes and from the curvature of inversion recovery intensity data. The experimental activation energy for jumps is comparable to the intramolecular potential barrier for rotation about phenylene vinylene bonds. ²H NMR provides a method for determining the phenylene-vinylene rotational barrier in pristine PPV, and may potentially be used to study conjugation in conducting films.     

高效液相色谱-荧光检测法测定土壤中的多环芳烃

多环芳烃(简称PAHs)是一类具有致癌、致畸以及能够诱导有机体突变的环境有机污染物。可靠的PAHs检测方法是研究其环境行为的重要保证。由于高效液相色谱-荧光检测法具有不需要高温、对某些PAHs有较高的分辨率和高灵敏度、柱后流出组分便于收集进行光谱鉴定等优点,近年来被广泛应用于PAHs的检测。实验在对美国环保局(USEPA)优先监测的15种PAHs污染物在土壤中的含量进行测定时,重点优化了梯度洗脱程序和检测波长程序。优化后的方法对15种PAHs的最低检出限为0.12～1.57 μg/kg,回收率为73%～126%,相对标准偏差为0.53%～3.57%。结果表明,该方法用于测定土壤中PAHs的含量,具有检出限低、灵敏度高和重复性好等优点,是一个较为可靠的检测方法。     

Determination of Linoleic Acid Oxylipins in Chinese Baijiu Using Ultra-Performance Liquid Chromatography with Quadruple-Time-of-Flight Mass Spectrometry (UPLC-QTOF-MS) and Nuclear Magnetic Resonance (NMR)

Linoleic acid oxylipins may adversely affect the quality of food products. To investigate the presence of linoleic acid oxylipins in Chinese Baijiu (distilled spirits), nine representative samples were analyzed using ultra-performance liquid chromatography coupled with quadruple-time-of-flight mass spectrometry (UPLC-TOF-MS) in the negative electrospray ionization (ESI) mode. For the first time, 12 oxylipins were identified in Baijiu via UPLC-TOF-MS and nuclear magnetic resonance spectroscopy (NMR). Moreover, a rapid and accurate internal standard (IS) quantification method was developed to determine these oxylipins in Baijiu by UPLC coupled with triple-quadrupole mass spectrometry. The method demonstrated acceptable precision, accuracy, and recovery, and was successfully applied to analyze the nine Baijiu samples. The afforded results indicated that in the soy sauce and strong aroma-type Baijiu samples, linoleic acid oxylipin was present in concentrations ranging from 1.27 to 104.90?μg/L; these values were significantly higher than those observed in the light aroma samples (P?<?0.01). This study proposes a quantitation method to monitor and control the linoleic acid oxylipin contents in Baijiu and provides new insights into the lipid metabolites of this distilled spirit.     

Conformation Changes of Enkephalin in Coordination with Pb2+ Investigated by Gas Phase Hydrogen/Deuterium Exchange Mass Spectrometry Combined with Theoretical Calculations

In this study, the effects of lead ions(Pb²⁺) on the conformations of leucine encephalin(LE) and methionine encephalin(ME) in gas phase were studied using hydrogen/deuterium exchange mass spectrometry(HDX-MS) and quantum chemistry theoretical calculations at the molecular level. The HDX-MS result revealed that the complexes with the monovalent compounds [LE+Pb–H]⁺ and [ME+Pb–H]⁺had a 1:1 stoichiometric ratio, and different HDX reactivates were observed in a follow of [ME+H]⁺>[LE+H]⁺>[LE+Pb–H]⁺> [ME+Pb–H]⁺. Combining the collision-induced dissociation energies of the complexes and their HDX results, it was found that the more stable the complex, the harder it was for HDX. In addition, the favo-rable conformations of the complexes were obtained by theoretical calculations, revealing that the similar coordination type with diffe-rent bond lengths was obtained. Then, the proton affinity(PA) values of the optimized complexes were calculated to interpret the HDX observations, indicating that the higher the PA values, the more difficult it was for HDX. Overall, the experiments and theoretical calculations revealed that Pb²⁺ could induce conformational changes of LE and ME, and generate ME into a more rigid conformation than LE. The results will prompt further fundamental investigations on the conformational properties of LE/ME in coordination with Pb²⁺.     

固相萃取-高效阴离子交换色谱-积分脉冲安培法检测人体尿液中的异黄蝶呤

建立了固相萃取-高效阴离子交换色谱-积分脉冲安培法(SPE-HPAEC-IPAD)测定人体尿液中异黄蝶呤的分析方法。尿液经ENVI-18与732型阳离子交换柱串联萃取后,除去了大量干扰物质。采用IonPac AS21分析柱(250 mm×2 mm),以0.025 mol/L NaOH溶液为淋洗液,流速为0.40 mL/min,在优化的安培检测波形条件下,异黄蝶呤的质量浓度在0.005～0.200 mg/L范围内与峰面积呈良好的线性关系,相关系数为0.998 4,检出限为0.003 mg/L。健康人及癌症病人尿液在2 mg/L和5 mg/L两个添加水平的平均回收率在95.4%～96.8%之间,相对标准偏差小于5%。此方法环保、快速、准确,可用于健康人与癌症病人尿液中异黄蝶呤的测定。     

阴离子交换色谱-脉冲安培法检测味精中的硫化物

建立了阴离子交换色谱柱分离、脉冲安培检测器测定味精中微量硫化物的方法。味精样品经2 g/L氢氧化钠溶液直接溶解并过滤后直接进样,硫离子与高浓度谷氨酸等阴离子在IonPac AS7阴离子色谱柱(250 mm×4 mm)上可实现较好的分离。以100 mmol/L氢氧化钠-500 mmol/L醋酸钠-0.5%乙二胺为淋洗液等度淋洗,6 min内可完成一次样品测定。脉冲安培检测器检测硫离子的检出限(25 μL进样,信噪比为3)为0.3 μg/L,并具有较宽的线性范围(0.001～1 mg/L),样品加标回收率为94.2%～99.0%。应用该方法检测99%味精、增鲜味精和加盐味精样品中的硫化物,结果表明该方法具有简便快捷、高选择性、高灵敏度等优点。     

Study on the reactivity of In2O3 in mixtures with ammonium-zeolites

In ground mixtures of In₂O₃ and NH₄Y, incorporation of In⁺ cations into the zeolitic phase occurs upon thermal treatment by partial reductive solid-state ion exchange associated with oxidation of ammonium ions or released ammonia to N₂ and NH₂OH. Cationic InO⁺ species, created in zeolites by reductive solid-state ion exchange of In₂O₃/NH₄-zeolite mixtures in hydrogen atmosphere and subsequent oxidation of the In⁺ lattice cations by oxygen, do not undergo autoreduction up to 970 K. Reductive solid-state ion exchange easily proceeds in carbon monoxide atmosphere at temperatures between 620 and 770 K. The significance of these observations for the use of indium-containing zeolites as catalysts is discussed.