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)

以0.01 mol·L-1PMBP萃取溶液可在pH5.5左右的溶液中将稀土(Ⅲ)萃取入有机相,从而与较大量的其他金属离子,如镁、铝、铬等分离。然后用稀盐酸将有机相中的RE(Ⅲ)反萃取入水相并在水相作稀土的光度测定。第三种方式是用较小体积的有机溶液从较大体积的水相中将RE(Ⅲ)的有色络合物萃取入有机相,这样由于有色络合物存在的溶液体积的缩小使其得到富集,其吸光度也相应地增大,而且这种吸光度的增大不仅由于体积的缩小,也由于有色络合物在有机溶剂中的离解度减弱,因为有机溶剂的介电常数通常比水小。例如RE(Ⅲ)与CPAⅢ所生成的有色螯合物在正…     

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     

双波长分光光度法测定水溶液中微量铋

测定水溶液中微量铋,原子吸收分光光度法是一种快速而灵敏的方法,但一般实验室尚无条件使用。常用的是双硫腙分光光度法。双硫腙与Bi(Ⅲ)离子生成橙红色螯合物,反应非常灵敏,且螯合物能被氯仿完全萃取。用氰化物作掩蔽剂时,方法的选择性良好。但双硫腙的氯仿溶液为绿色,生成的螯合物为橙红色,试液中含有两种有色成份,它们的吸收峰又部份重叠。随着试液中Bi(Ⅲ)含量的增加,双硫腙的绿色变浅,螯合物的橙红色加深。两种有色成份的含量都是变数,因此背景吸收不能用固定量的双硫腙(空白溶液)来消除,     

废水中微量铀的偶氮胂Ⅲ萃取光度测定

偶氮胂Ⅲ萃取光度测定铀(Ⅳ) ,操作简单、选择性高,但还未见用于测定水样中微量铀。本文试验了从含二苯胍的水溶液中用氯仿丁醇混合溶剂萃取铀(Ⅵ)偶氮肿Ⅲ络合物的萃取条件、萃取络合物的组成和共存离子的干扰。用建立的方法测定了稀土水冶厂废水和个别山区井水中微量铀。并采用在萃取后的有机相中加入少量盐酸丁醇混合液,使络合物的最大吸收峰紫移5毫微米,而表观克分子吸收系数提高到5.0×10~4。方法磷酸根容许量高,相对均方差±2.4％,铀回收率为96-99％。     

TbCl_3-DyCl_3-HCl-H_2O-P507体系的萃取平衡数学模型和最优工艺的选择

本文研究了TbCl_3-DyCl_3-HCl-H_2O-P507体系的萃取平衡关系,关联了分配比模型:(1)以水相中稀土总浓度的分区模型;(2)以摩尔分数的分区模型;(3)铽和镝的模型。利用上述模型研究了铽镝二元体系的萃取行为,其与单一铽或镝相比,由于第二元素的存在导至了分配比、分离因数和有机相的稀土浓度的变化。利用水相稀土浓度的分区模型,进行了分馏萃取静态特性模拟。探索了影响分离工艺的因素、研究了萃取因数与分离效率的关系和在实际中达到材料消耗低和分离效率高的最优条件。提出了达到铽>95％和镝>99.5％的最优分离工艺。     

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)

稀土元素的4f电子层受配位场的影响,较易形成离子型螯合剂,这种与偶氮胂Ⅲ所形成的呈色螯合物的吸收光谱趋向红移。偶氮胂Ⅲ[Ar(Ⅲ)]试剂在游离状态时,它的分子结构是对称的。但由于胂酸基团的空间位阻效应,分子的左右两部分不在一个面上,它与稀土离子的螯合反应只有一个分析特征功能结构参与,即螯合反应只在分子的一侧发生,因而使分子的对称性破坏,这一现象的产生也使其色泽有所加深,而且在试剂与稀土离子的螯合物形成后产生了在可见光区内出现两个吸收峰,一个峰位于610 nm左右,是不与稀土离子反应的功能结构所引起的;另一个峰位于665 nm…     

偶氮氯膦Ⅲ双波长分光光度法测定奶粉中的Fe(Ⅲ)

在酸性介质中,Fe(Ⅲ)与偶氮氯膦Ⅲ反应生成具有明显正吸收峰和负吸收峰的螯合物,最大正吸收波长位于670nm,最大负吸收波长位于530nm,用双波长叠加测定,表观摩尔吸光系数(ε)为5.93×10~4 L/(mol·cm),线性范围为0.2~2.00mg/L,探讨了适宜的反应条件、考察了准确度、精密度及选择性。该方法用于奶粉中Fe(Ⅲ)的测定,结果令人满意。     

偶氮氯膦Ⅲ与稀土元素显色反应的量子化学研究

本文用INDO/F方法,通过大量计算得到稀土离子 La~(3+)、Ce~(3+)、Pr~(3+)、Nd~(3+)、Sm~(3+)、Gd~(3+)与偶氮氯膦Ⅲ(CPAⅢ)的络合位置和 CPAⅢ的配位原子,并对其稳定性及电子结构进行了研究,最大波长吸收峰对应的跃迁是电荷迁移光谱.计算结果与实验有很好的一致性.     

重稀土与偶氮氯膦Ⅲβ型反应动力学研究及机理的探讨

一定条件下,偶氮氯膦Ⅲ的重稀土螯合物可由α型转化成β型。连续扫描的谱图表明:α型是瞬时形成的。随着反应进行,α峰下降而β峰上升。在恒溫、Yb:R=1:1和pH=3.2时,测得非缓冲体系和缓冲体系(NaAc—HCl)的反应级数分别为2和1,表观活化能分别为71.1KJ/mol和49.8KJ/mol。对于许多缓冲体系,具有亲核基团的缓冲介质能够加速此转化过程。在此缓冲体系中,β型螯合物的生成速率随氢离子浓度的增大而减小,随缓冲介质浓度增大而增大。实验还表明:两个α型分子形成一个β型分子并释放出一个质子。据此,对缓冲体系和非缓冲体系分别拟出了合理的机理,稳态处理后的动力学速率方程满意地解释了所有实验事实。最后讨论了反应机理的可能模式。     

反胶团二壬基萘磺酸萃取镁的机理研究

为了确定反胶团二壬基萘磺酸萃取水相中Mg~(2+)的过程机理,以二壬基萘磺酸为萃取剂、磺化煤油为稀释剂所组成的反胶团有机相对水中的Mg~(2+)进行了萃取研究。考察了反胶团的皂化率、水相中镁盐阴离子种类等对萃取率的影响,同时考察了萃取温度、水相中pH值对分配比的影响,萃取饱和容量随萃取剂浓度的变化情况以及Mg~(2+)在两相中的分配情况。研究结果显示,反胶团的皂化率、水相中镁盐阴离子种类对萃取过程无明显影响;萃取分配比随萃取温度的升高而增大;在萃取体系中水相pH值低于4时,分配比随pH值的增加而增大,pH值大于4后,分配比变化幅度较小;萃取饱和容量随萃取剂浓度的增加而增大,且与萃取剂浓度呈线性关系。二壬基萘磺酸从水相介质中萃取Mg~(2+)的过程是吸热反应,其萃取过程热效应(?H)为5.135k J/mol。研究表明,反胶团二壬基萘磺酸萃取Mg~(2+)的过程为阳离子交换,这一研究结果为二壬基萘磺酸从冶金废水中萃取回收镁提供了理论基础和借鉴。     

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).     

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.     

Electrochemical Fluorination of Benzamide and Acetanilide in Anhydrous HF and in Acetonitrile

Electrochemical fluorination of benzamide in anhydrous hydrogen fluoride does not involve the amide group but occurs exclusively at the aromatic ring, yielding isomeric fluoro- and difluorobenzamides and 3,3,6,6-tetrafluoro-1,4-cyclohexadienecarboxamide. Electrochemical fluorination of benzamide in acetonitrile as solvent gives the same products, as well as benzonitrile and its fluorinated derivatives and products of hydrolysis and fluorination of acetonitrile. Electrochemical fluorination of acetanilide in anhydrous HF leads to complete tarring of the reaction mixture, while its fluorination in acetonitrile results in selective formation of m-fluoroacetanilide.     

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.