核磁共振定量法测定恩曲他滨绝对含量

分别采用氢核磁共振定量法和氟核磁共振定量法测定恩曲他滨绝对含量。氢核磁共振定量法以恩曲他滨δ8.32~8.40处质子峰和对苯二甲酸二甲酯δ8.12处为定量峰,在恒温27℃,采样时间4.01 s,弛豫延迟时间10 s,扫描次数为64条件下采集氢谱。氟核磁共振定量法以4'-溴-2'-氟-乙酰苯胺为内标,在恒温27℃,谱宽为29 296.87 Hz,中心频率为-54 667.50 Hz下采集氟谱。结果显示,氢核磁共振定量法和氟核磁共振定量法测定结果基本与质量平衡法结果一致。因此,核磁共振法测定恩曲他滨绝对含量具有专属性高、准确、快速等优势。     

草甘膦水剂中草甘膦的定量检测

论述了草甘膦水剂中草甘膦的定量检测方法,采用了核磁共振的分析方法和内标定量.该方法对样品的前处理没有特殊要求,可以达到快速、准确的定量目的.     

近十年定量核磁共振法应用研究进展

介绍了近十年国内外各类定量核磁共振法在各领域的研究进展。定量核磁共振法(qNMR)作为一种选择性强、准确快捷的定量分析方法，广泛应用于有机化合物的纯度定值。核磁共振法主要分为一维谱(¹H、¹³C、¹⁹F、³¹P-NMR)、二维谱、液相色谱-核磁共振联用法(LC-NMR)、固体NMR等类型。其中，¹H谱是最常用的定量核磁共振方法，广泛应用于各领域；其他一维谱中的分析物信号通常较少或没有杂质干扰，近年也常用于食品、药学等领域。二维谱和LC-NMR联用技术则可以对复杂样品进行定量分析。固体qNMR针对固体样品前处理简便，但相较于液体qNMR研究较少。     

核磁共振定量技术测定原薯蓣皂苷对照品的含量

目的:1H核磁共振定量技术测定原薯蓣皂苷的含量。方法:采用Bruker AVANCEII 500MHz超导脉冲傅里叶变换核磁共振波谱仪,以氘代吡啶为溶剂、TMS为内标,测定原薯蓣皂苷的核磁共振氢谱,通过样品定量峰与内标物质响应峰面积及质子当量重量,计算原薯蓣皂苷的含量。结果:以化学位移为δH5.84处的氢信号作为定量峰,其含量测定的重复性、精密度、稳定性、耐用性的RSD值均小于2%。测得3批原薯蓣皂苷样品的绝对含量分别为98.56%、98.43%、98.63%。结论:在没有对照品的情况下,核磁共振内标法可用于原薯蓣皂苷的含量测定。     

核磁共振测井背景介绍与发射时序分析

核磁共振测井是一种有效的石油探测新技术。与常规电、声、核辐射等测井方法相比,核磁共振测井信号来自地层孔隙流体,包含十分丰富的地层信息,可用于定量确定自由流体、束缚水、渗透率以及孔径分布等重要参数,而且,其孔隙度测量不受岩石骨架矿物成分的影响。本文主要介绍了核磁共振测井的相关背景,并对其发射时序进行简要介绍与分析。     

核磁共振氢谱法测定注射用微球专用溶剂中硅油的含量

目的：建立测定注射用微球专用溶剂中硅油含量的定量核磁共振氢谱(qHNMR)法。方法：采用Bruker Avance NEO 600型核磁共振波谱仪测定核磁共振氢谱(¹H NMR),脉冲序列zg30,弛豫延迟时间15 s,采样次数16,测定温度25℃,以咖啡因为内标,不加四甲基硅烷(TMS)的氘代氯仿为溶剂,对注射用微球专用溶剂中的硅油进行定量研究,以硅油定量峰与内标定量峰面积之比对其含量(μg)绘制标准曲线,计算注射用微球专用溶剂中硅油含量。结果：硅油含量在6～100μg范围内线性关系良好,r=0.999 9,低、中、高浓度的平均回收率为97.8%(n=9),重复性RSD为9.8%。结论：该方法操作简单快捷、灵敏度高、结果准确,可用于注射用微球专用溶剂中硅油含量的测定。     

Py-GCMS和NMR联用在涂料乳化剂未知组分剖析中的应用

介绍了热裂解气相色谱-质谱(Py-GCMS)、核磁共振谱(NMR)在未知结构的涂料乳化剂配方剖析中的应用。其中,核磁共振包含多种方法,分别是氢谱(1H NMR)、碳谱(13C NMR)、二维核磁共振谱(2D NMR)、扩散排序技术(DOSY NMR)以及定量核磁共振(QNMR)。通过以上方法的联用,对未知乳化剂各成分进行了定性和定量分析,得到了配方中主体成分和溶剂的种类及含量,为未知混合物配方的剖析提供了一种新思路。     

现代仪器分析在聚氨酯中的应用（连载六）：核磁共振在聚氨酯结构研究中的应用（一）

聚氨酯是一种发展迅速、性能优异的高分子材料。在合成过程中，所用原料种类繁多，工艺各异，得到的聚合物结构复杂，性能各不相同，因此鉴定其结构，对研究结构与性能的关系以及开发新产品都是至关重要的。核磁共振正是此类研究不可缺少的一种手段。核磁共振对于聚合物构型与构象的分析，对于立体异构体的鉴定，对于共聚物的组成定性、定量以及序列结构测定有独特的长处，许多信息是其他方法难以提供的。本文仅对核磁共振基本原理，核磁共振在聚氨酯工业中对所用原料、预聚体到各类产品的结构研究，如在组成成分定性、定量、端基分析。序列…     

用~(13)C-和~1H-核磁共振谱进行赤平煤吡啶抽出物的结构分析

赤平煤吡啶抽出物的石油醚可溶份用氧化铝柱色谱分成5个级分(A—E),每个级分用~(13)C-和1H-核磁共振谱进行分析。此外,由~1H-核磁共振谱和定量的~(13)C-核磁共振谱、元素分析和平均分子量的结果计算出级分B-E的平均结构参数。定量的~(13)C-核磁共振谱是由乙酰丙酮酸铬松弛试剂和门控去偶联用进行测定。     

定量核磁共振技术的测试流程

随着核磁共振技术的发展,定量核磁共振技术(Quantitative Nuclear Magnetic Resonance,QNMR)广泛应用于制药、食品、生命科学、化工等领域,已成为一种重要的分析方法。结合日常工作,文章综述了QNMR的原理、内标峰和内标物的选择、实验参数设置以及实施方法,为迅速、顺利地开展QNMR实验提供参考。     

Effect of carbonation on the hydro-mechanical properties of Portland cements

We evaluate experimentally the effect of carbonation on the hydro-mechanical properties of Portland cement. Samples were carbonated at 90 °C and 28 MPa under wet supercritical CO₂. Two types of carbonation features were achieved, either the samples were homogeneously carbonated or they displayed sharp carbonation fronts. Using a tri-axial apparatus, the static elastic moduli and the mechanical strength were measured at in-situ pressure conditions (28 MPa) and showed a degradation of the mechanical properties of the samples where a carbonation front prevailed. Water and gas permeabilities were measured and showed that the samples with a carbonation front exhibit a stress sensitive permeability. P and S elastic wave velocities were measured to evaluate dynamic (ultrasonic range, 1 MHz) elastic moduli. The use of an effective medium theory approach enabled us to characterize the density and distribution of cracks within the samples. This approach outlines that the samples which developed a carbonation front were damaged.     

Influence of the nature of aggregates on the behaviour of concrete subjected to elevated temperature

An experimental study is carried out on concretes composed of three different types of aggregates: semi crushed silico-calcareous, crushed calcareous and rolled siliceous. For each aggregate type, two water/cement ratios (W/C), 0.6 and 0.3 are studied. Aggregates and concrete specimens were subjected to 300, 600 and 750 °C heating–cooling cycles. We analyse the evolution of thermal, physical and mechanical properties of concrete in terms of behaviour and physical characteristic evolutions of aggregates with temperature. The study of thermal behaviour of aggregates showed the importance of initial moisture state for the flints. The crystallisation and microstructure of quartz play an important role in the thermal stability of siliceous aggregates. The residual mechanical behaviour of concrete varies depending on the aggregate and the influence of aggregates is also dependent on paste composition. This study allowed to better understand the influence of chemical and mineralogical characteristics of aggregates on the thermomechanical behaviour of concrete.     

Assessment of the long-term stability of cementitious barriers of radioactive waste repositories by using digital-image-based microstructure generation and reactive transport modelling

Cement-based grout plays a significant role in the design and performance of nuclear waste repositories: used correctly, it can enhance their safety. However, the high water-to-binder ratios, which are required to meet the desired workability and injection ability at early age, lead to high porosity that may affect the durability of this material and undermine its long-term geochemical performance.In this paper, a new methodology is presented in order to help the process of mix design which best meets the compromise between these two conflicting requirements. It involves the combined use of the computer programs CEMHYD3D for the generation of digital-image-based microstructures and CrunchFlow, for the reactive transport calculations affecting the materials so simulated. This approach is exemplified with two grout types, namely, the so-called Standard mix 5/5, used in the upper parts of the structure, and the “low-pH” P308B, to be injected at higher depths.The results of the digital reconstruction of the mineralogical composition of the hardened paste are entirely logical, as the microstructures display high degrees of hydration, large porosities and low or nil contents of aluminium compounds.Diffusion of solutes in the pore solution was considered to be the dominant transport process. A single scenario was studied for both mix designs and their performances were compared. The reactive transport model adequately reproduces the process of decalcification of the C-S-H and the precipitation of calcite, which is corroborated by empirical observations. It was found that the evolution of the deterioration process is sensitive to the chemical composition of groundwater, its effects being more severe when grout is set under continuous exposure to poorly mineralized groundwater. Results obtained appear to indicate that a correct conceptualization of the problem was accomplished and support the assumption that, in absence of more reliable empirical data, it might constitute a useful tool to estimate the durability of cement-based structures.     

New method for determination of absorption capacity of internal curing agents

Accurate assessment of absorption capacity (k) of internal curing agents is necessary to properly proportion cement-based mixtures and to measure their effectiveness in mitigating autogenous shrinkage. Standard methods for quantifying absorption capacity, such as those for coarse and fine aggregate, are not appropriate for the highly absorptive, finely divided materials often used for internal curing. Here, it is demonstrated that the absorption capacity of internal curing materials may be determined from early age heat evolution data measured through isothermal calorimetry. An example application, using pulp fibers as internal curing agents, is used to demonstrate the utility of the method.     

Effects of mixing state of composite powders on sintering behavior of cathode for solid oxide fuel cells

For efficient development of high-performance composite electrodes for solid oxide fuel cells (SOFCs), it is crucial to precisely tailor the microstructural features of the electrodes, such as their grain size, phase connectivity, and pore structure. Herein, we report the effects of the mixing state of component powders of a composite cathode composed of Sr-doped LaMnO₃ (LSM) and yttria-stabilized zirconia (YSZ) on its sintering behavior. LSM-YSZ composite powders were synthesized by a particle-dispersed glycine-nitrate process using YSZ particles as inclusions in the LSM precursor solution. The dispersion state of the YSZ particles in the solution was varied from a well-dispersed state to a highly flocculated state through adjustment of the amount of adsorbed polyethylene glycol. The dispersion state of the component powders was found to strongly impact the densification behavior of the composite, which was explained by the formation of a continuous network of the “slow-sintering” inclusion particles. A highly porous structure with phase connectivity and sufficient triple phase boundaries could be achieved by enhancing the mixing homogeneity and optimizing the mixing scale. The proposed concept provides new insights into the microstructural evolution of composites in constrained sintering, and it could potentially enable development of the ideal electrode structure for SOFCs.     

Modelling of ageing effects on crack-bridging behaviour of AR-glass multifilament yarns embedded in cement-based matrix

This article focus on modelling of ageing effects on crack-bridging behaviour of AR-glass multifilament yarns embedded in cement-based matrix. In the first step, age-dependent changes in the crack-bridging behaviour of AR-glass multifilament yarns were investigated at the meso and micro levels. Two cementitious matrices were considered where the binder contained Portland cement clinker and ground granulated blast furnace slag cement, respectively. Mechanical characteristics of the bond between matrix and multifilament yarns after accelerated ageing were measured by means of double-sided yarn pullout tests. In these tests the multifilament yarns bridged a single crack in the matrix arising in a notched area of the specimen. Losses in performance with increasing age differed widely depending on matrix material composition. The essential cause of such losses was discovered to be the microscopic densification of the fibre-to-matrix interface. This led to increased bond intensity and restricted slip-ability of the filaments. Subsequently, these micro-structural phenomena were related to the mesoscopic material behaviour by means of a phenomenological bond model. This cross-linkage model describes the crack-bridging effect of the entire multifilament yarn at the single filament level. According to the model, each filament possesses a specific deformation length depending on its position in the cross-section of the yarn. This deformation length depends on bond characteristics between single filament and cementitious matrix, which vary with age. Characteristic values of the model were computed from load-crack width curves obtained from the yarn pullout tests. The changes in the microstructure were represented by the characteristic values of the model.     

Influence of chemical degradation on mechanical behavior of a petroleum cement paste

Cement paste used in the Oil Industry is generally subjected to chemical degradation due to flow of acid fluids in various situations. The present study focuses on the evolution of thermo-hydro-mechanical (THM) behavior with chemical degradation of petroleum cement paste. Triaxial compression tests with different confining pressures (0, 3, 10 and 20 MPa) are carried out on a standard oil cement paste in sound state and completely degraded state by ammonium nitrate solution under a temperature of 90 °C. The results obtained show that the material in its initial state exhibits a small elastic phase and a strong capacity of compaction. The mechanical behavior depends on the load induced pore water pressure. Because of the increase in porosity caused by chemical degradation, the mechanical strength (cohesion and friction angle) and Young's modulus decrease. The dependence of mechanical strength and Young's modulus on confining pressure is smaller in the chemically degraded cement paste than in the sound one. In fine, the mechanical behavior of the whole material becomes more ductile. As a result, such effects of chemical degradation should be taken into account when modeling such cement paste materials exposed to such chemical degradations.     

Effect of fibre morphology on flocculation of fibre–cement suspensions

The objective of the present research was to evaluate the effect of fibre morphology (e.g., length, width, fibrillation, broken ends, content of fines and number of fibres per gram) on flocculation and drainage properties of fibre–cement suspensions and on physical properties of the fibre–cement composites. Mechanical refining was used to change the morphological properties of Eucalyptus and Pinus pulps. Results show that the mechanical refining increased the size of the formed flocs and decreased the concentration of free small particles (with dimensions between 1 and 20 µm) as a consequence of the increased fibrillation and content of fines, which increased the capacity of the fibres to capture the mineral particles. High levels of refining were necessary for Pinus pulp to obtain cement retention values similar to those obtained by unrefined Eucalyptus pulp. This is due to the higher number of fibres per gram in Eucalyptus pulp than in Pinus pulp. Pulp refining improved the packing of the particles and, although decreased the drainage rate, it contributed to a less porous structure, which improved the microstructure of the composite.     

Effect of maturation time on the fresh and hardened properties of an air lime mortar

The restoration and maintenance of old renders is one of the key aspects of correct rehabilitation practice. The ideal course of action is to replace the damaged material by a material with compatible characteristics. This work aims to analyze the effect of the maturation process on hardened state characteristics of hydrated powder lime mortars. The rheological characterization shows an air lime mortar thickening behaviour with the length of the test. The different mixes were subjected to a maturation process consisting on keeping them in the fresh state, covered with water, isolated from CO₂, during seven days. The specimens and applications were prepared both with the non-matured and the matured mortars. Maturation seems to influence the hardened state characteristics causing a decrease in the capillary values, and an increase on the mechanical strength, which are more evident for mortars with higher binder contents.     

Resistivity of cementitious materials measured in diaphragm migration cells: The effect of the experimental set-up

Experimental measurements and numerical analysis were carried out to study the effect of the cell geometry in resistivity determinations. The resistance of the diaphragm in cement paste and mortar samples was determined using impedance spectroscopy. Numerical simulations were performed using finite element method (FEM). Several surface ratios (geometrical diaphragm surface to electrolyte-diaphragm surface, S/S′) were investigated. The thickness of the diaphragm, L, was also considered.The experimental results show a significant decrease of the apparent resistivity when the ratio S/S′ increases. Similar trend was observed for increasing values of the L/S′ ratio. The numerical simulations can explain the experimental findings and also allow to formulate a general rule for the design of migration and diffusion experiments in porous materials.