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）

上节中已提到了CPAⅢ与RE(Ⅲ)离子所生成的螯合物具有比偶氮胂Ⅲ的螯合物更好的光度分析特性,可归纳为以下几点:(1)可在较高一些的微度条件下反应;(2)所生成的螯合物有较高的稳定性;(3)所生成的螯合物的吸收峰向长波方向移动,其色泽的深度和强度明显增加,且与CPAⅢ试剂色泽之间     

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)

稀土(Ⅲ)与CPAⅢ生成的α型螯合物的可萃取性也是一种很有实用意义的特征。在pH 1.1~1.5的酸度条件下反应生成的α型螯合物可用正丁醇萃取。螯合物在有机相中吸光度可稳定至少24 h。与在水溶液的显色反应比较,螯合物在有机相中呈出3项特点:①稳定性好;②在水溶液中各单一稀土(Ⅲ)离子的螯合物的吸收峰波长略有差异,而在正丁醇中吸收峰的波长无差异,均为668 nm;③在正丁醇介质中,各单一稀土(Ⅲ)螯合物的摩尔吸光系数的值比在水溶液中的值高3倍左右;其值从镧至镝随原子序数增大而增加,而从镝至镥却随原子序数增大而减小(表6-21)。由于CPAⅢ…     

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）

2.3.2 EDTA与稀土离子的螯合物的稳定性根据软硬酸碱的概念,稀土离子属硬酸,EDTA分子中的羧基属硬碱,其所含的氨基属中间碱,因此它们之间可形成稳定或较稳定的螯合物,在螯合反应中,三价稀土离子与EDTA分子中的氧原子和氮原子相键合,生成多个五员环结构。螯合物的组成比都是1∶1。由于在日常分析中都用EDTA的二钠盐(Na2H2Y·2H2O)配制滴定剂溶液,溶解度较酸式的EDTA大,在22℃时,每100 mL水中可溶解11.1 g固体,此溶液的浓度约为0.3 mol·L-1,酸度约为pH4.7。因此,在写反应式时也可用H2Y2-代表EDTA,它与稀土离子的反应式可写作:R…     

偶氮胂Ⅲ螯合形成树脂分离富集岩石中微量稀土元素

近年来有人用螯合形成树脂分离富集重金属离子。国外曾报导过偶氮胂Ⅲ螯合形成树脂,但未用于稀土元素的分离富集。本文用偶氮胂Ⅲ水溶液与D_(296)大孔强碱性阴离子树脂经简便搅拌而制得偶氮胂Ⅲ(Ars-Ⅲ)螯合形成树脂。研究了该树脂分离富集微量稀土元素的条件。在抗坏血酸及EDTA-Zn存在下,树脂能较好地分离干扰元素,柱上分离时间1小时左右。岩石样经本法分离富集后,用偶氮胂Ⅲ分光光度法测稀土总量,结果满意。     

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)

表6-21稀土(Ⅲ)与CPAⅢ的α型螯合物的光吸收特性在强酸性溶液中因质子化而可能出现以下两种形式上:式中R为-AsO目前,在成熟的分析方法中常用的试剂有偶氮氯膦-pN,偶氮氯膦-mN,偶氮氯膦-mA等几种。具有不对称结构的变色酸双偶氮类显色剂的优良分析性能与其分子结构有关。此类试剂在分子结构上的不对称性,使分子两端电子云分布不均匀且易于极化;在试剂分子中引入了电负性较大的助色基团,导致产生强烈的诱导效应,例如在偶氮氯膦型试剂的分子中,-PO3H2为较强的成盐基团,在-PO3H2基团的间位上,也就是在偶氮基的对位上引入了电负性较强的氯…     

稀土-偶氮胂Ⅲ-铜-邻菲罗啉混合多核配合物显色反应的研究

在弱酸性介质中,稀土与偶氮胂Ⅲ所形成的阴离子配合物,可以与金属-邻菲罗啉配阳离子通过静电引力形成缔合型的混合多核配合物。本文详细地研究了镧-偶氮胂Ⅲ-铜-邻菲罗啉配合物的形成条件以及有关反应机理。配合物的最大吸收峰位于663nm,相应的摩尔吸光系数ε_(663)=1.22×10~5 L·mol~(-1)·cm~(-1)。配合物中各组分的摩尔比La:R:Cu:Phen=1:1:1:3,相应的分子式为[La·R][Cu(phen)_3]。反应曾应用于以铜为主的合成试样中稀土的测定,取得了比较满意的结果。     

偶氮胂Ⅲ螯合形成树脂的特性

作者曾将偶氮胂Ⅲ(Ars-Ⅲ)通过其结构中的磺酸基负载到D296大孔强碱性阴离子交换树脂(简称D296树脂)上,制成偶氮胂Ⅲ螯合形成树脂(简称Ars-Ⅲ树脂),并研究了该树脂分离富集稀土元素的条件。本文则试验了Ars-Ⅲ树脂的特性,分别考察了pH对D296树脂吸着Ars-Ⅲ的影响,D296树脂吸着Ars-Ⅲ的平衡速率;作了Ars-Ⅲ树脂吸着稀土元素与D296树脂吸着Ars-Ⅲ-RE螯合物的对照试验:探讨了Ars-Ⅲ树脂的稳定性、吸附容量、Ars-Ⅲ树脂吸着非稀土元素的能力及Ars-Ⅲ试剂用量的影响。     

DCS-偶氮胂与稀土元素显色反应的应用研究—牧草中微量稀土的测定

本文研究了DCS-偶氮胂与稀土元素的显色反应。DCS-偶氮胂具有高的灵敏度(对稀土总量ε=1.00～1.30×105)和好的选择性。试剂和配合物定,它们的最大吸收峰分别在530nm和630nm处。RE_xO_y在0—3μg/25ml范围内符合比尔定律,结合PMBP萃取法,可用于测定牧草中微量稀土。本方法简单、快速、准确,结果满意。     

稀土螯合物发光体LB膜的研究(I)

稀土有机配合物的发光研究近年来取得了可喜的近展.铕(Ⅲ)、铽(Ⅲ)、钐(Ⅲ)与β-二酮(β-dik),三正辛基氧化膦(TOPO)所形成的螯合物,以及它们的硝酸盐与邻菲咯啉(Phen)所形成的螯合物都是高光效的发光体,有广阔的应用前景,在某些方面已获得应用.如能把这些具有发光功能的稀土螯合物组装成有序的分子组合体,则很可能在分子光学技术,光电子技术等领域发挥重要作用.如何组装?本文用LB 膜技术,通过交替成膜或混     

牡蛎源类蛋白反应修饰肽的分离纯化及肽锌螯合物的结构表征

以牡蛎为原料制备了类蛋白反应修饰肽,利用Sephadex G-15凝胶层析柱和反向高效液相色谱(RP-HPLC)等分离技术得到1条锌离子螯合活性为161 mg/g的多肽(M_w=835),多肽序列为EVPPEEH.以测得的肽序列为模板合成多肽,将纯肽与锌离子进行螯合反应制备肽锌螯合物.螯合物的红外光谱和圆二色光谱表征结果表明,锌离子主要与多肽链上的羰基氧发生相互作用.与多肽的空间结构相比,螯合物的无规则卷曲结构减少,β转角增加而β折叠减少.由肽锌螯合物的分子模拟和二级质谱结果可知,多肽与锌离子螯合后有2种空间构象:一种通过六配位的方式螯合1个锌离子,其中主要的螯合位点为多肽Val-2和Pro-3或者Glu-5和Glu-6之间的羰基氧;另一种是通过四配位的方式螯合1个锌离子,主要的螯合位点为多肽Glu-5和Glu-6之间的羰基氧.     

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...     

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).     

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.     

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.     

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.     

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.