DBC-偶氮氯膦固相光度法测定稀土元素铈,铕,钇

在2 mol/L HCl介质中,Ce(Ⅲ),Eu(Ⅲ),Y(Ⅲ)与DBC-偶氮氯膦形成的络合物吸附到201×7型强碱性苯乙烯阴离子树脂上。最大吸收波长Ce(Ⅲ)络合物为648 nm,Eu(Ⅲ)络合物为650 nm,Y(Ⅲ)络合物为650 nm。Ce(Ⅲ)络合物表观摩尔吸光系数为6ε48 nm=9.6×104L.mol-1.cm-1,Eu(Ⅲ)络合物表观摩尔吸光系数为6ε50 nm=1.51×105L.mol-1.cm-1,Y(Ⅲ)络合物表观摩尔吸光系数为6ε50 nm=5.6×104L.mol-1.cm-1。固相光度法测定Ce(Ⅲ),Eu(Ⅲ),Y(Ⅲ)质量浓度在0~0.48μg/mL范围内与吸光度值呈良好线性关系。该法可用于分子筛中Ce的测定。     

阴离子交换色谱-积分脉冲安培检测法分离测定烟草料液中的山梨醇和糖

采用阴离子交换色谱-积分脉冲安培检测法分离测定了烟草料液中山梨醇、葡萄糖、果糖、蔗糖和麦芽糖,研究了山梨醇和糖在阴离子交换色谱中的保留行为。采用优化的水和氢氧化钠二元梯度淋洗条件,CarboPac PA10阴离子交换色谱柱进行分离,积分脉冲安培检测器检测一次进样测定烟草料液样品中的山梨醇、葡萄糖、果糖、蔗糖和麦芽糖。各组分在测试条件下线性关系良好,线性范围为0.005～20 mg/L,检测限为0.2～1.0 μg/L,加标回收率为95.1%~102.4%,相对标准偏差为1.2%～1.9%。     

纤维素酶降解-离子色谱法测定魔芋中的亚硝酸盐

建立了以纤维素酶降解魔芋葡甘聚糖释放阴离子,然后采用离子色谱测定亚硝酸盐含量的方法。考察了纤维素酶降解葡甘聚糖的最佳条件,结果表明:在50 ℃、pH 5.5条件下酶解24 h,可以释放出被包埋的亚硝酸盐。NO-2的检出限为0.039 mg/L,回收率为96.7%～97.8%。运用本法对施用稀土微肥后魔芋中亚硝酸盐的含量进行测定,发现施用稀土微肥能够在一定程度上降低魔芋中亚硝酸盐的含量。     

树脂分离光度法测定金、钯、铂

用 Amberlyst A-26大孔阴离子交换树脂分离金(Ⅲ)、铂(Ⅳ)和钯(Ⅱ).在 HAc-NaAc缓冲液中,用易溶于水的显色剂N-烯丙基-N′-(对氨基苯磺酸钠)硫脲(ASATu)和N-间甲苯基-N′-(对氨基苯磺酸钠)硫脲(MMPT)测定.前者测定金(Ⅲ),后者同时测定铂(Ⅳ)和钯(Ⅱ).该法用于催化剂和阳极泥...     

氧化银沉淀-离子色谱法测定海水中的痕量亚硝酸根和硝酸根

海水中痕量亚硝酸根、硝酸根的含量是评价海水的富营养化的重要指标,采用离子色谱法可对它们进行同时测定。但海水中大量的Cl^-和SO4^2-会干扰海水中微量NO2^-和NO3^-的测定。目前,在用离子色谱法分析阴离子时排除Cl^-干扰的有效方法是银柱法,但银柱价格较贵,成本较高,使得银柱法的使用在国内受到限制。本实验以固体Ag2O和Ba（OH）,为沉淀剂,采用氧化银沉淀法排除Cl^-和SO4^2-的干扰。用此方法对海水处理后,再用离子色谱法检测NO2^-和NO3^-,不仅结果令人满意,检测费用也大大低于银柱法。     

氧瓶分解—离子色谱法测定胱氨酸标准物质中的硫

介绍了用氧瓶分解－离子色谱测定胱氨酸标准物质中硫元素含量的方法。以美国进口胱氨酸标准物质为样品,用氧瓶燃烧分解,以碱性吸收液吸收,使硫元素转化为硫酸根阴离子,然后进行离子色谱分析。分析数据与标准物质标称值进行了比较,结果令人满意。     

微波消解-电感耦合等离子体发射光谱(ICP-OES)法测生物质中的碱金属和碱土金属

为研究并解决测试生物质样品中碱金属和碱土金属含量的干扰,采用微波消解-电感耦合等离子体发射光谱(ICP-OES)法对生物质中的碱金属和碱土金属钾、钙、钠、镁元素进行测定,考察了样品消解后不同的酸体系,共存元素干扰对钾、钠、钙、镁含量测定的干扰研究。经过研究表明,接近分析标准曲线酸浓度的样品干扰小,铅、铟、钛、锰元素对钠元素测定造成干扰,砷、铜、镉对钙元素测定干扰,铝对钾元素测定有干扰,镁测定不受共存元素干扰影响,运用干扰系数法可以减少共存元素对测定元素的误差。各待测元素标准曲线相关系数大于0.9996,检出限为0.0014~0.023 mg/L,玉米芯各元素的相对标准偏差为0.98%~1.9%,加标回收率为80.2%~106%;西瓜皮的各元素相对标准偏差为0.91%~2.3%,加标回收率为85.3%~106%。方法用于测定国家标准物质GBW07603,各元素结果均在标准值参考范围内。方法用于测定生物质中碱金属和碱土金属的结果,用t检验法与离子色谱测定值进行比对,结果无显著性差异。     

以氯醌酸二价阴离子为桥联配体的Fe(Ⅲ)-Fe(Ⅲ)和Mn(Ⅱ)-Mn(Ⅱ)双核配合物的合成与磁性

基于铁和锰的双核配合物在生物氧化还原过程中的重要作用及在化学的氧化还原过程中可能做为催化剂的应用前景,本文合成了两个新的以氯醌酸二价阴离子为桥联配体的Fe(Ⅲ)双核和Mn(Ⅱ)双核配合物:[Fe_2(phen)_4(μ-CA)](ClO_4)_4·2H_2O(1)和[Mn_2(phen)_4(μ-CA)](ClO_4)_2·3H_2O(2)(phen=1,10菲咯啉;CA=氯醌酸二价阴离子)。经元素分析、IR、电子光谱及磁性等测定,对两配合物进行了表征。     

模糊聚类-偏最小二乘算法应用于分光光度法同时测定铁、镍、钒、铜、钴

对铁(Ⅲ)、镍(Ⅱ)、钒(Ⅴ)、铜(Ⅱ)及钴(Ⅱ)五种金属离子分别与5-Br-PADAP在OP存在下且在pH 3.5的乙酸盐缓冲溶液中的显色反应进行了研究。结果表明,每一离子与5-Br-PADAP螯合物的吸收光谱严重重叠,使各元素的光度测定受到相互严重干扰。将模糊聚类-偏最小二乘算法应用于此反应体系的计算,使光谱重叠及光度分析计算中的校正模型的优化问题得到有效的解决。在最佳反应条件下并应用模糊聚类-PLS算法,可实现上述5种元素的同时光度测定。用5个模拟样进行回收率试验,5个元素的回收率结果在93.3%~105.5%之间。将此方法应用于原油样品中5种元素的测定,所得结果与AAS法所测得结果相符。     

反相高效液相色谱法测定化妆品中L-抗坏血酸磷酸镁含量

L-抗坏血酸磷酸镁(AS-PM)用在化妆品中作增白剂和抗辐射剂。AS-PM是极性分子,通常使用一个阴离子交换柱进行色谱分离,本文用四氢呋喃。磷酸盐缓冲溶液溶解稀释化妆品样品后,在氨丙基柱上以乙腈一磷酸盐缓冲溶液为流动相测定其中的AS-PM。     

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.     

钙与人体及临床

钙是宏量元素，是人体中含量较高的元素之一，体内99％的钙构成骨骼和牙齿以及维持骨骼结构，1％的钙调节人体重要生理功能。钙的含量过高或过低都与许多疾病有关，只有保持一种平衡状态，才能使机体处于正常环境。     

Structure Formation and Molecular Mobility in Water and in Aqueous Solutions

The study of the structure of water and of aqueous solutions has recently received new impetus from the efforts at commercial desalineation of sea water and from developments in molecular biology. The current view that, apart from single molecules, water contains only one type of structural element, namely “flickering” network structures with tetrahedrally hydrogen-bonded water molecules (two-states model) is proving inadequate in the interpretation of new experimental data and in the calculation of thermodynamic functions. After a critical discussion of the basis of this model and of the concept of hydrogen bonds, a second kind of structural element, i.e. a third state, is suggested: small aggregates of molecules containing mainly non-tetrahedral hydrogen bonds as well as some tetrahedral ones, and packed more densely than allowed by the lattice-like structure. These aggregates – dimers to hexamers – can be regarded as the primary products of disruption of the network structures, and displace the latter as structural components in water with increasing temperature or concentration of solutes. This “combined” model allows a consistent interpretation of the properties of water and of the various effects of dissolved substances.     

Advances in amperometric and conductometric detection in capillary and chip-based electrophoresis

Amperometric and conductometric detection are currently the two major electrochemical detection modes in capillary and chip electrophoresis. The ease of miniaturization and integration of electrochemical detection elements offers a high potential for the development of portable analytical devices based on electromigrative separations. The challenges and basic concepts of both detection principles in the context of capillary/chip electrophoresis are shortly introduced and milestones of the methodical developments are summarized from a historical perspective. Recent advances and applications are discussed with more detail. Particular attention is paid to new trends in this area of research such as measurements in short capillaries and the enormous progress and increased popularity of contactless conductivity detection. Correspondence: Frank-Michael Matysik, Institute of Analytical Chemistry, University of Leipzig, Linnéstr. 3, D-04103 Leipzig, Germany     

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.     

Carbon chains and rings in the laboratory and in space

Seventy-seven reactive organic molecules of astrophysical interest have been identified in a supersonic molecular beam, 73 in the radio band by Fourier-transform microwave spectroscopy, four in the optical by laser cavity ringdown spectroscopy. Most are linear carbon chains, but six consist of carbon chains attached to the compact, highly polar C3 ring, and two are rhomboidal cyclic configurations of SiC3. The laboratory astrophysics of the radio molecules is complete for the time being, in the sense that essentially all the rotational transitions of current interest to radio astronomy (including hyperfine structure when present) can now be calculated to a small fraction of 1 km s(-1) in equivalent radial velocity; six of the radio molecules have already been detected in space on the basis of the present data. The FTM spectrometer employed in this work is far from fundamental limits of sensitivity, so many more molecules can probably be found by refinements of present techniques. The density of reactive molecules in our supersonic beam is generally high by the standards of laser spectroscopy, and many of the radio molecules probably have detectable optical transitions which we are attempting to find, largely motivated by the long-standing problem of the diffuse interstellar bands. Our most interesting result to date is the detection of a fairly strong molecular band at 443 nm in a benzene discharge, in exact coincidence with the strongest and best known interstellar band. Isotopic shifts measured with partially and totally deuterated benzene suggest that the carrier of the laboratory band is a hydrocarbon molecule with the elemental formula CnH5, with n most likely in the range 3-6.     

Femtosecond electron-transfer reactions in mono- and polynucleotides and in DNA

Quenching of redox active, intercalating dyes by guanine bases in DNA can occur on a femtosecond time scale both in DNA and in nucleotide complexes. Notwithstanding the ultrafast rate coefficients, we find that a classical, nonadiabatic Marcus model for electron transfer explains the experimental observations, which allows us to estimate the electronic coupling (330 cm(-1)) and reorganization (8070 cm(-1)) energies involved for thionine-[poly(dG-dC)](2) complexes. Making the simplifying assumption that other charged, pi-stacked DNA intercalators also have approximately these same values, the electron-transfer rate coefficients as a function of the driving force, DeltaG, are derived for similar molecules. The rate of electron transfer is found to be independent of the speed of molecular reorientation. Electron transfer to the thionine singlet excited state from DNA obtained from calf thymus, salmon testes, and the bacterium, micrococcus luteus (lysodeikticus) containing different fractions of G-C pairs, has also been studied. Using a Monte Carlo model for electron transfer in DNA and allowing for reaction of the dye with the nearest 10 bases in the chain, the distance dependence scaling parameter, beta, is found to be 0.8 +/- 0.1 A(-1). The model also predicts the redox potential for guanine dimers, and we find this to be close to the value for isolated guanine bases. Additionally, we find that the pyrimidine bases are barriers to efficient electron transfer within the superexchange limit, and we also infer from this model that the electrons do not cross between strands on the picosecond time scale; that is, the electronic coupling occurs predominantly through the pi-stack and is not increased substantially by the presence of hydrogen bonding within the duplex. We conclude that long-range electron transfer in DNA is not exceptionally fast as would be expected if DNA behaved as a "molecular wire" but nor is it as slow as is seen in proteins, which do not benefit from pi-stacking.