新显色剂对乙酯基偶氮氯膦的合成及其与钇的β反应研究和应用

本文报道了新显色剂对乙酯基偶氮氯膦的合成及其与稀土元素显色反应的研究。试剂在pH3.5的HAc-NaAc介质中能与钇生成β型络合物。吸收峰位于726nm波长处。摩尔吸光系数ε=4.48×10~4L·mol~(-1)·cm~(-1)。6～14μg/25ml钇量符合比耳定律。用光度法直接测定了纯锌中的微量钇,结果令人满意。     

金属材料分析方法的选择和施行 第六讲 金属材料中稀土元素的测定(续)

了解稀土元素在镁合金中的作用及其加入量对试验、提高或改进镁合金中稀土元素的测定方法是有利的。从以上的叙述可知稀土元素可以单一稀土（钇、铈或钕等）的形式或以混合稀土的形式加入于镁合金中；含量低至w（RE）0．15％，高至4％（我国镁合金）和10％（美国标准）。因此镁合金中稀土的测定方法应能适应合金的实际情况。     

金属材料分析方法的选择和施行 第六讲 金属材料中稀土元素的测定（续）

2金属材料中稀土元素的测定2.1重量测定法重量测定法常应用于稀土元素含量较高的合金的分析。可用稀土-硅-镁中间合金作为例子说明稀土总量的重量测定法在这种合金的分析中的应用。稀土硅镁之间合金的主成分是硅、稀土、铁和镁,同时还含少量或微量的钙、锰、钛、铝、磷等元素。此外,由于稀土矿源不同,可能会含有某些特殊元素。例如包头稀土矿还给合金带入一定量的钍。表1中列举了几种稀土-硅-镁合金标准物质的组份,供参考。根据这一合金的组成,在最终进行稀土元素的沉淀、灼烧及称量之前必须先使稀土与共存的干扰测定的元素分离,然后选择一…     

如何找出各稀土元素与显色剂所生成的配合物的共吸收点作为稀土总量的测定波长，从而解决制作工作曲线时稀土标准溶液的配制问题？

在相同的反应条件下，两种或多种金属离子与同一种显色试剂所生成的配合物，在吸收光谱上出现的共吸收点(或称等吸收点)，在常规光度法中被用作测定这些金属离子总量的检测波长，在双波长光度法中则可选用此波长作为参比波长。在测定金属材料中的稀土总量时，利用各稀土元素与同一显色剂所生成的配合物的共吸收点作为测定稀土总量的测定波长，     

简讯

双波长标准加入吸光光度法同时测定锌汞国防科技大学研究了一种利用化学计量学原理改善分析方法选择性的计算分析方法——双波长标准加入吸光光度法(简称双标法)。双波长吸光光度法用于多组分相互干扰体系的测定,主要有等吸收点法和系数倍率法等。这两种方法通常是测量信号下降以消除共存物干扰,改善选择性,但在一定程度上     

读者园地

问 :如何找出各稀土元素与显色剂所生成的配合物的共吸收点作为稀土总量的测定波长 ,从而解决制作工作曲线时稀土标准溶液的配制问题 ?山东读者———张立答 :在相同的反应条件下 ,两种或多种金属离子与同一种显色试剂所生成的配合物 ,在吸收光谱上出现的共吸收点 (或称等吸收点 ) ,在常规光度法中被用作测定这些金属离子总量的检测波长 ,在双波长光度法中则可选用此波长作为参比波长。在测定金属材料中的稀土总量时 ,利用各稀土元素与同一显色剂所生成的配合物的共吸收点作为测定稀土总量的测定波长 ,也是解决工作曲线的通用基准的一种有效…     

强制流动液相色谱分离-分光光度测定合金钢和高温合金中痕量稀土、钇和锆

稀土和钇等元素对高温合金的性能有良好的改善,检测高温合金中痕量稀土和钇是很有实际意义的。目前用分光光度法测定成份复杂合金中稀土和钇时,缺乏灵敏度高、选择性好的显色剂。因此,在测定前需要进行分离。本文探讨了用强制流动液相色谱进行离子交换,盐酸-乙醇作淋洗剂,使稀土、钇、锆与高温合金中其他元素分离,在所拟定的条件下还可使样品中钇与少量稀土相分离。实验方法     

可变误差多面体法测定铝合金中钇及稀土总量

本文把计算机和分光光度法结合起来,根据DBC-偶氮氯膦与稀土元素形成有色配合物的吸光系数之间的差异,把十五个稀土元素分为六个组分(加上显色剂共七个组分),利用可变误差多面体法对数据进行处理,以期解决铝合金中钇及稀土总量的测定问题。实验结果令人满意。     

ICP-光电手动扫描快速测定合金中钇钆镧铈

由于稀土元素的化学性质极其相似,测定合金中稀土元素的含量是一项重要而且复杂的分析任务。目前国内外最常用的有重量法、容量法、比色法、发射光谱法、原子吸收法。ICP-AES法已广泛用于测定合金成份与合金中的杂质元素。本文用ICP-光电手动扫描装置以及小型可编程序计算器处理数据。试样溶解后,用纯溶液标样直接快速测定钛合金、钨合金、钼合金、铜合金中的稀土元素。测定合金中的镧(1.8%)、铈(0.3%)、钇(0.1%)、钆(0.3%)的变异系数分别为1.13%,1.04%,2.17%,1.92%。通过实际试样的配合分析,证明本方法简单、快速、准确可靠。     

对马尿酸偶氮氯膦直接光度法测定钢铁中稀土总量的研究

对马尿酸偶氮氯膦是武汉大学最近合成的稀土新显色剂,其结构式为: 我们对该试剂与稀土元素显色反应条件和用于测定钢铁中稀土总量进行了研究。该试剂在0.02～0.5N各种酸介质中,均能与稀土元素立即反应生成兰色稳定络合物。络合物的最大吸收波长位于680nm左右。各稀土元素(La～Lu、Y)的络合物的摩尔吸光系数为(7.27～10.22)×10~4·1·mol~(-1)。cm~(-1)。该试剂的主要特点在于它与稀土元素反应具有显色酸度高、灵敏度较高。选择性和稳定性较好,允许共存元素量也较高。控制适当条件,它与铈和钇所形成的络合物的吸光度是一致的。所以它是一种目前测定稀土总量较为理想的试剂。即使有较大量EDTA、酒石酸以     

Generation and detection of levuglandins and isolevuglandins in vitro and in vivo

Levuglandins (LGs) and isolevuglandins (isoLGs), formed by rearrangement of endoperoxide intermediates generated through the cyclooxygenase and free radical induced oxidation of polyunsaturated fatty acids (PUFAs), are extraordinarily reactive, forming covalent adducts incorporating protein lysyl ε-amino groups. Because they accumulate, these adducts provide a dosimeter of oxidative injury. This review provides an updated and comprehensive overview of the generation of LG/isoLG in vitro and in vivo and the detection methods for the adducts of LG/isoLG and biological molecules in vivo.     

Enthalpies of solution of purine and adenine in water and in dimethylsulfoxide

Journal of Solution Chemistry - Enthalpies of solution of purine and adenine in water and in demethylsulfoxide were measured calorimetrically in the temperature range 25–40°C. ΔH s...     

Coassembly of Nanorods and Nanospheres in Suspensions and in Stratified Films

The entropically driven coassembly of nanorods (cellulose nanocrystals, CNCs) and nanospheres (dye‐labeled spherical latex nanoparticles, NPs) was studied in aqueous suspensions and in solid films. In mixed CNC‐latex suspensions, phase separation into an isotropic latex‐NP‐rich and a chiral nematic CNC‐rich phase took place; the latter contained a significant amount of latex NPs. Drying the mixed suspension resulted in CNC‐latex films with planar disordered layers of latex NPs, which alternated with chiral nematic CNC‐rich regions. In addition, fluorescent latex NPs were embedded in the chiral nematic domains. The stratified morphology of the films, together with a random distribution of latex NPs in the anisotropic phase, led to the films having close‐to‐uniform fluorescence, birefringence, and circular dichroism properties.     

Determination of diazepam and nordazepam in milk and plasma in the presence of oxazepam and temazepam

For studies on the excretion of drugs into milk a sensitive high-performance liquid chromatographic assay was developed to quantitate diazepam and nordazepam in the milk and plasma of humans and rabbits in the presence of their major metabolites, oxazepam and temazepam. Flurazepam was used as an internal standard. The assay involves extractions with diethyl ether and an additional acid clean-up step. Chromatographic separation was achieved by a LiChrospher 60 RP-select B (5 microns) column and KH2PO4- acetonitrile (69:31, v/v) adjusted to pH 2.80 as a mobile phase. The same extraction and chromatographic conditions were suited to both types of samples, milk and plasma. The limits of determination using ultraviolet detection at 241 nm was for diazepam 20 ng/ml and for nordazepam 15 ng/ml. The absolute recoveries of diazepam, nordazepam and flurazepam in human milk were 84, 86 and 92% and in human plasma 97, 89 and 94%, respectively. The within- and between-day accuracy and precision for diazepam and nordazepam in milk and plasma at all concentrations tested (20-1500 ng/ml) were better than 8%. The high fat content which occurs in rabbit milk presented no limitation for the extraction of lipophilic diazepam: the method was successfully used to monitor milk and plasma concentrations of diazepam and nordazepam in lactating New Zealand White rabbits during 26-h infusions of diazepam (1.4 mg/h).     

Structure of dimethoxyamine in the crystalline and gaseous phases and in solution

Conclusions It has been established by the methods of x-ray diffraction analysis and electron diffraction analysis and measurements of the dipole moments and the birefringence that in the crystalline and gaseous phases, as well as in solution, N,N-dimethoxyamine has a gauche-gauche conformation, which is stipulated by a stabilizing nO-N-O* orbital interaction. The geometric parameters of the molecule have been determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2235–2242, October, 1986.     

Comparison and correlation of in vitro, in vivo and in silico evaluations of alpha, beta and gamma cyclodextrin complexes of curcumin

In the present study investigated the effect of curcumin (CUR) alpha (α), beta (β) and gamma (γ) cyclodextrin (CD) complexes on its solubility and bioavailability. CUR the active principle of turmeric is a natural antioxidant agent with potent anti-inflammatory activity along with chemotherapeutic and chemopreventive properties. Poor solubility and poor oral bioavailability are the main reasons which preclude CUR use in therapy. Extent of complexation was β-CD complex (82 %) > γ-CD (71 %) > α-CD (65 %). Pulverization method resulted in significant enhancement of CUR (0.002 mg/ml) solubility with CUR α-CD complex (0.364 mg/ml) > CUR β-CD complex (0.186 mg/ml) > CUR γ-CD complex (0.068 mg/ml). Gibbs-free energy and in silico molecular docking studies favour formation of α-CD complex > β-CD complex > γ-CD complex. With reference to CUR, relative bioavailability of CUR α-CD, CUR β-CD and CUR γ-CD complexes were 460, 365 and 99 % respectively. CUR–CD complexes exhibited increased bioavailability with an increase in t_½, tmax, Cmax, AUC, Ka, and MRT; and a decrease in Ke, clearance and Vd values. AUC increase was CUR α-CD complex > CUR β-CD complex > CUR γ-CD complex. Significant difference (p < 0.05) was observed between CUR α-CD complex and CUR γ-CD complex by one-way ANOVA and Dunnett’s post hoc test for multiple comparison analysis. Correlation observed between in vitro, in vivo and in silico methods indicates potential of in silico and in vitro methods in CD selection.     

Homo- and hetero-complexes of exchangeable apolipoproteins in solution and in lipid-bound form

The self-association state of human plasma apolipoprotein E (apoE) in solution and in complexes with dimyristoylphosphatidylcholine (DMPC) varying in stoichiometry was studied in sub-micromolar concentration range by gel filtration, fluorescence anisotropy, fluorescence quenching and energy transfer measurements with apolipoprotein labeled with lysine-specific fluorescent dyes. Together, these results confirm the equilibrium scheme for various apoE structures in solution: oligomer (in aged preparations) <==> 'closed' tetramer <==> 'open' tetramer ('molten globule' state) <==> native or partially denatured monomer <==> fully denatured monomer. Within DMPC:apoE discoidal complex (125:1) the apolipoprotein association state seems to be intermediate between that in solution and in larger vesicular complex (1000:1); for both complexes, the degree of exposure of fluorescein chromophores into water phase decreased. Hetero-associates of apoA-I and apoC-III-1 in solution and in the complexes with DMPC appear to behave similarly to apoE. When extrapolated to native HDL particles, 'molten globule' state seems to be a structure responsible for the interaction of exchangeable apolipoproteins with phospholipid. For a first time, the location of various apolipoprotein molecules on disc periphery was confirmed. The lysine residue(s) seems to locate closely to reacting residue(s) within apolipoprotein molecules in associates, however, with different package constraints for discoidal versus vesicular complexes with phospholipid.     

Fluorimetric quantification of clodronate and alendronate in aqueous samples and in serum

The bisphosphonates clodronate and alendronate are drugs in the therapy of osteoporosis or Paget's disease. They are highly hydrophilic and therefore of low oral bioavailability. Determination methods for bisphosphonates are often laborious and expensive equipment is needed. The presented quantification method based on kinetic measurement of the fluorescence decrease of an Al³⁺-morin complex can be used to determine the bisphosphonate content in aqueous and plasma samples. The intra- and inter-assay accuracies were found to be within 98.8% and 102.3% of the target samples for clodronate and within 97.2% and 105.0% of the target samples for alendronate. The LOQ was defined as 15.6 ng/ml for clodronate and 62.5 ng/ml for alendronate. In serum samples, intra- and inter-assay accuracy was found to be within 99.0% and 101.6% of the target samples for clodronate and within 97.8% and 102.6% of the target samples for alendronate. In serum samples, the LOQ was defined as 1.55 mg/ml for clodronate and 0.39 mg/ml for alendronate. Though less sensitive in serum, the presented method could support research on the development of drug delivery systems in vitro and in vivo for the investigated and other structurally related bisphosphonates.