光度法连续测定铝合金中的铜铁

本文介绍了在同一溶液中用二环已酮草酰双腙(BCO)光度法测定铜和磺基水扬酸(SaL)光度法测定铁的分析方法,铜和铁显色后的吸收峰分别是(?)=600nm,(?)=430nm,互不干扰,实现了连续测定.方法的精确度高,且稳定性和重现性好.其灵敏度分别为ε_(cu)=1.6×10~4.ε_(Fe)=9×10~3.1 试验部分1.1 试剂与仪器721A型分光光度计H_2O_2:30%柠檬酸铵、磺基水杨酸:50?O:0.025%,称取0.25g BCO溶于热乙醇100ml中,冷却后以水稀释至1L.铜和铁混合标准溶液:分别移取含铜、铁均为0.500mg.ml~(-1)的标液各25ml于250ml量瓶中,以水稀释至刻度,摇匀.此溶液中含铜和铁各50μg·ml~(-1).     

微量元素与帕金森病

帕金森病是世界公认的第二大神经系统疾病,我国目前的患病人数已超过245万,已成为影响我国人口健康水平的重大社会问题。帕金森病的病因至今不清。该文在分析该病流行状况、危险因素的基础上,探讨了微量元素与帕金森病的相关关系,以及微量元素组学研究用于该病预警和早期诊断的可能性。     

火焰原子吸收光谱法测定苦黄注射液及其中药材中五种金属元素

用硝酸和过氧化氢消化样品，通过基体改进剂，使用火焰原子吸收光谱法测定苦黄注射液及其中药材大黄、茵陈、柴胡、苦参中铜、铁、锌、钾和钠的含量。方法的回收率在92．6％～112．1％之间，相对标准偏差小于4％。     

重铬酸钾滴定法测定废杂铜中的铁含量

研究了废杂铜中铁含量的测定方法.试料采用盐酸、硝酸、高氯酸溶解,加入过量氨水生成氢氧化铁沉淀与铜、铬等干扰元素分离,沉淀用热盐酸溶解后,用氯化亚锡还原至溶液呈浅黄色,重铬酸钾滴定法测定铁含量.探讨了溶样方式、氯化铵用量、氨水过量的体积、硫磷混酸用量对测定结果的影响.对4个废杂铜样品中的铁含量进行测定,测定结果的相对标准...     

流动注射在线柱预富集-电感耦合等离子体原子发射光谱测定痕量金属元素

本文报道了流动注射在线柱预富集ICP光谱测定痕量金属的方法,以meso-四(4-磺基苯)卟啉为柱前衍生试剂,硅胶作固定相和盐酸作洗脱液,对痕量金属离子Cu、Mn、Ni、Fe、Pb、Cd进行在线预富集检测。在给定实验条件下,方法的富集倍数为9.3～11.3,检出限和测定的相对标准偏差(n=6)分别在0.32～26.8ng/ml和1.3％～3.0％范围内。方法用于小牛肝和西红柿叶样品分析,结果与参考值吻合。     

火焰原子吸收光谱法测定天佛参口服液及其原料药中五种金属元素

样品经硝酸和过氧化氢消化,用火焰原子吸收光谱法测定其中铜、铁、锌、钾和钠5种金属元素的含量。为克服共存组分的干扰,测定铁（Ⅲ）须在盐酸（2＋98）溶液中进行,测定锌（Ⅱ）则应在正丁醇-水（6＋94）溶液中进行,测定铜（Ⅱ）、钾（Ⅰ）及钠（Ⅰ）则在硝酸（2＋98）溶液中进行。上述各溶液的总体积均为250mL。应用此法分析...     

碘量法连续测定选矿废水中的铜铁

针对选矿废水中的铜离子和铁离子,在滴定铜离子含量的基础上,向滴定液中继续加入三氯化铝溶液作为解蔽剂将铁离子解蔽,此时溶液呈深棕色,以硫代硫酸钠标准溶液继续滴定铁,溶液深棕色消失转为奶白色即为滴定终点,避免了单独滴定铜铁含量的麻烦,且在滴定铁离子含量时无需除铜。经实验验证,对选矿废水中铁含量进行滴定与重铬酸钾滴定铁含量的结果一致,相对误差小于2.03%,加标回收率在95.8%~101.9%,相对标准偏差(RSD,n=10)在0.48%~1.5%。方法精密度高,重现性好,简便快捷,可以满足选矿废水中铜、铁含量的测定要求。     

火焰原子吸收法测定癌细胞中的钙、镁、铜等金属元素

采用火焰原子吸收法直接测定一系列(食道、胃)癌细胞及其近旁的正常细胞中的钙、镁、铜等金属含量。结果表明,钙的变异系数为1．83％-4．19％,回收率为99．8％-104．0％;镁的变异系数为0．02％～1．18％,回收率为97．2％-98．5％;铜的变异系数为3．80％-6．68％,回收率为90．5％～99．7％;均得到较满意的结果,具有一定的参考价值。     

Application of Synchrotron Radiation in Neuromicrobiology: Role of Iron in Parkinson's Disease

In order to understand the role of iron (Fe) in the oxidative stress underlying the pathogenesis of Parkinson's disease (PD) and parkinsonism–dementia complex (PDC), we investigate distributions and chemical states of Fe within a single neuron of the two disease cases, using synchrotron radiation (SR) micro beam. In the X-ray fluorescence (XRF) spectroscopic study, an excessive accumulation of Fe can be seen in the melanized neurons and free-neuromelanin (MN) aggregates in the substantia nigra tissue of both PD and PDC midbrains. X-ray absorption near-edge structure (XANES) analyses of PD revealed that the chemical state of Fe in the melanized neurons and free-MN aggregates shifted toward Fe³⁺ with a pre-edge peak at Fe K-edge due to a 1s 3d transition, indicating a breaking of the inversion symmetry around the Fe site. In PDC, however, the melanized neurons and free-MN aggregates showed mixed states of Fe²⁺ and Fe³⁺ without any pre-edge peak in the spectra. This tendency was also observed in the control case. These results suggest that the changes in distributions and chemical states of Fe may endogenously play a crucial role in the oxidative damage of the melanized neurons in PD, but through a different mechanism other than PDC.     

Extinction correction and synchrotron radiation

The primary extinction factor y_p is defined as the ratio of the integrated reflection from a coherently diffracting domain to the integrated kinematical reflection from the same domain. When y_p is larger than 0.5 it may be approximated by y_p = exp{−(αδ)2}, where α is about 0.5 andδ the average size of the coherent domain when measured in units of the extinction length A,δ = D/λ. Transfer equations are applied to symmetrical Laue diffraction, and the reflectivity per unit length, Σ(ε) is solved from the measured reflecting ratio as a function of the rocking angleε =θ− θ_B. Measurements with conventional x-ray sources are made on single crystal slabs of Be and Si using AgKΒ, MoKα₁ and CuKα radiation. The primary extinction factor y_p(ε) is solved from a point-by-point comparison of two measurements where the extinction length λ is changed by varying the polarization and/or wavelength of the x-ray beam. The results show that primary and secondary extinction are strongly correlated, and that the customary assumption of independent size and orientation distributions of crystal mosaics is unjustified. The structure factors for Be and Si show close agreement with other recent measurements and calculations. The limitations of the method are discussed in length, particularly the effects of beam divergences and incoherence of the rays in the crystal. It is concluded that under typical experimental conditions the requirements of the theory are met. Practical limitations arising from the use of characteristic wavelengths and unpolarized radiation prohibit the use of the full potential of the method. The properties of a synchrotron radiation source are compared with a conventional x-ray source, and it is demonstrated that the experimental limitations can be removed by the use of synchrotron radiation. A diffraction experiment with synchrotron radiation is outlined, as well as generalization of the method to small spherical crystals.     

Histidine‐Rich Oligopeptides To Lessen Copper‐Mediated Amyloid‐β Toxicity

Brain copper imbalance plays an important role in amyloid‐β aggregation, tau hyperphosphorylation, and neurotoxicity observed in Alzheimer's disease (AD). Therefore, the administration of biocompatible metal‐binding agents may offer a potential therapeutic solution to target mislocalized copper ions and restore metallostasis. Histidine‐containing peptides and proteins are excellent metal binders and are found in many natural systems. The design of short peptides showing optimal binding properties represents a promising approach to capture and redistribute mislocalized metal ions, mainly due to their biocompatibility, ease of synthesis, and the possibility of fine‐tuning their metal‐binding affinities in order to suppress unwanted competitive binding with copper‐containing proteins. In the present study, three peptides, namely HWH , HK^CH , and HAH , have been designed with the objective of reducing copper toxicity in AD. These tripeptides form highly stable albumin‐like complexes, showing higher affinity for Cu^II than that of Aβ(1‐40). Furthermore, HWH , HK^CH , and HAH act as very efficient inhibitors of copper‐mediated reactive oxygen species (ROS) generation and prevent the copper‐induced overproduction of toxic oligomers in the initial steps of amyloid aggregation in the presence of Cu^II ions. These tripeptides, and more generally small peptides including the sequence His‐Xaa‐His at the N‐terminus, may therefore be considered as promising motifs for the future development of new and efficient anti‐Alzheimer drugs.     

Dissociative photoionization of Al2(Ch3)6 and Al2(Ch3)3Cl3 in the range 40–100 eV

Dissociation processes of the organoaluminum compounds Al₂(CH₃)₆ and Al₂(CH₃)₃Cl₃ have been studied in the range of valence and Al:2p core-level ionization by means of photoelectron–photoion and photoion–photoion coincidence techniques. The double-ionization threshold and the Al:2p core-ionization threshold of Al₂(CH₃)₆ are estimated to be about 30 and 80 eV

1 1 eV = 96.4853 kJ mol^?1.

respectively. The relative yields of the H⁺?Al⁺ and H⁺?CH_m,⁺ (m′ = 0–3) ion pairs are enhanced around the Al:2p core-ionization threshold of Al₂(CH₃)₆. The photoion–photoion coincidence intensities of Al₂(CH₃)₃Cl₃ are negligibly small throughout the energy range studied. The ratio of the relative yield of AlC₂H₆⁺ to that of Al⁺ increases smoothly through the Al:2p core-ionization and/or excitation region of Al₂(CH₃)₃Cl₃. The variation of the fragmentation pattern with photon energy is discussed in conjunction with the relevant electronic states.     

同步辐射在稀土发光材料研究中的应用

介绍了同步辐射用于稀土发材料研究的基本概况，主要包括以下方面：（1）利用同步辐射极宽的光谱分布研究稀土发光的激发谱（35－300nm)和选择激发下的发射谱。（2）利用同步辐射快脉冲光（ps级）研究选择激发下的发光衰减规律，荧光寿命；（3）利用高强度同步辐射X射线研究材料的晶体结构与成分，特别是微结构。以CeF3闪烁体为例说明发射光谱及其衰减规律对激发光波长的强烈依赖：以BaF2:Gd,Eu对例说明获得高效率稀土发光的新途径一“量子剪裁”，以纳米Y2O3：Eu为例，说明发光的尺寸效应与发光中心微结构的关系。     

微量元素铁与蛋白质酪氨酸硝化

蛋白质酪氨酸硝化是一氧化氮依赖的氧化应激的生物标志。蛋白质硝化将会直接影响蛋白质的催化活性、细胞信号传递和细胞骨架结构,导致相关病症的发生发展。本文介绍了铁在不同酪氨酸硝化途径中的作用,结果提示体内的微量铁对蛋白质硝化起着重要作用。