THE USE OF LIQUID CHROMATOGRAPHY-MASS SPECTROMETRY TO MONITOR THE ALLOMERIZATION REACTIONS OF CHLOROPHYLL a and PHEOPHYTIN a:m IDENTIFICATION OF THE ALLOMERS OF PHEOPHYTIN a

Abstract— This paper reports a new method for monitoring the allomerization reactions of chlorophyll a and pheo-phytin a. Complex mixtures are generated from illuminating pure compounds and monitored using both diode array high-performance liquid chromatography (DAD-HPLC) and liquid chromatography-mass spectrometry (LC-MS). LC-MS allows molecular weight and fragment ion analysis of significant HPLC peaks. Five products of the degradation of chlorophyll a can be simultaneously detected in a mixture, namely the monohydroxy allomer, the methoxylactone allomer, pheophytin a and the two corresponding allomers of the pheophytin. It is demonstrated that more than one pathway must be involved in the in vitro photodegradation of chlorophyll a as shown by the simultaneous existence of several intermediates.     

气相色谱-质谱联用法分析羰基硫的纯度

利用气相色谱-质谱联用法对羰基硫纯气进行纯度分析。采用质谱扫描直接对杂质化合物进行定性分析,确定了羰基硫纯气中的杂质气为二氧化碳、硫化氢和氮气。选择了单点外标法和归一化法定量测定了羰基硫纯气中二氧化碳、硫化氢和氮气的摩尔分数,并对其不确定度进行了评价,得到羰基硫纯气中羰基硫的摩尔分数为(0.9855±0.0040)mol/mol。     

苯基重氮盐-冠醚分子嵌合物的FAB-MS及其准分子离子生成机理的研究

苯基重氮盐质谱研究曾有报导,它同冠醚分子形成的嵌合物质谱也被测定过。本文采用快原子轰击(FAB)研究了苯基重氮盐,(R=OCH_3,CH_3,H,Br,Cl,F,NO_2)同18-冠醚-6以及二苯并-24-冠醚-8形成分子嵌合物的质谱(MS),讨论这类嵌合物准分子离子MNa~ 丰度同嵌合物内授-受键的性质之间的关系,并由分子轨道方法计算结果解释了MNa~ 的丰度同苯基重氮盐上取代基R性质的关系。     

第四级铵氢氧化物Hofmann消除反应的构象分析及反应机理

本文用DPCILO, CNDO程序分别计算了一些第四级铵离子不同构象的能量及电荷密度, 探讨Hofmann消除反应的机理, 结果表明构象规则能较好地说明Hofmann消除反应的机理, 只是“直链型”烷基的消除反应应按顺式E_2机理进行。     

高效液相色谱法检测冷冻烤鳗中恩诺沙星等药物残留

论述了高效液相色谱法检测冷冻烤鳗中恩诺沙星、环丙沙星、诺氟沙星等合成抗菌剂残留的方法。样品以乙腈为提取剂,经脱脂、浓缩、净化,用流动相溶解。高效液相色谱荧光检测器测定。各标准曲线线性范围为0.005～1.000mg·kg-1,回收率为86.2%～92.3%,检出限分别为1,2,2μg·kg-1。     

主成分回归法同时测定油品中铁钴镍钒

用主成分回归法,自编程序在计算机上处理数据,同时测定油品中铁、钴、镍、钒。以OP-5-Br-PADAP为显色体系,用调节pH值的方法消除油品中共存元素的干扰。人工合成样品的回收率在94.3％～105.0％间,油样测定结果的相对标准偏差在2.0％～4.5％间。铁、钴、镍、钒的摩尔吸光系数分别为1.1×10~5,1.0×10~5,1.0×10~5,3.6×10~4。该法快速、准确、灵敏度高。     

甲醇POSR制氢的反应网络热力学分析和有效因子的估算

在Cu/ZnO/Al2O3催化剂上对甲醇部分氧化蒸汽重整制备氢气反应的动力学过程进行了研究。在常压和473 K～1 073 K温度范围内对该反应网络中的甲醇部分氧化、甲醇蒸汽重整、甲醇分解和水煤气反应的化学平衡进行了分析。在对这些反应的催化剂Cu/ZnO/Al2O3动力学研究的基础上，根据有效因子的基本概念，考虑催化剂颗粒内的扩散限制，对每个反应沿反应器床层的有效因子进行了估算。     

Ni－B超细非晶合金的化学制备、反应机理及性质研究

本文研究了水溶液中ＮｉＣｌ２与ＫＢＨ４的反应及其产物Ｎｉ－Ｂ超细非晶合金的性质。详细探讨了反应的电化学基础和反应过程机理。发现Ｎｉ＾２＋与ＢＨ＾－４的反应独立的基本反应组成，其中不可避免地存在ＢＨ＾－４的分解即与Ｈ２Ｏ的反应，Ｎｉ－Ｂ则产生于Ｎｉ＾２＋的还原     

Ni－B超细非晶合金的化学制备、反应机理及性质研究

本文研究了水溶液中ＮｉＣｌ２与ＫＢＨ４的反应及其产物Ｎｉ－Ｂ超细非晶合金的性质，详细探讨了反应的电化学基础和反应过程及机理．发现Ｎｉ（２＋）与的反应由三个独立的基本反应组成，其中不可避免地存在的分解即与Ｈ２Ｏ的反应，Ｎｉ－Ｂ则产生于Ｎｉ（２＋）的还原（被）和离子内部的氧化还原反应．反应中，反应液的ｐＨ值可自动恒定在３．１８左右．在总包反应中，完全还原１ｍｏｌＮｉ（２＋）需要消耗１．８４ｍｏｌ，其中的分解反应约占４８％．根据反应机理可计算产物的组成，计算结果与实际测定值完全一致．电镜测定表明，反应产物呈非晶态，粒径约４００．     

用气-质联用技术检测葱、蒜、韭菜中多种农药残留量时试样预处理方法

采用气相色谱及质谱联用技术,测定葱、蒜及韭菜等蔬菜中多种农药残留量时,在粉碎试样之前,用磷酸或微波加热处理试样,可使蒜酶钝化并消除其基体干扰。试验结果显示,或用磷酸处理,或经微波加热处理,均能有效消除高背景的干扰。试样在粉碎前经磷酸预处理,在所测定的75种农药中有90％以上农药的回收率达到70％～120％之间。     

316名健康儿童血清锌、铜正常参考值调查分析

用原子吸收法对淮阴市区幼儿园316名健康儿童,进行了血清锌、铜含量的测定,建立了正常参考值范围。儿童血清锌、铜正常含量分别为0.941±0.210μg/mL、1.276±0.225μg/mL。儿童血清锌、铜在男女之间无显著性差异(P>0.05)。     

FLUORESCENCE LIFETIMES OF CHLOROPHYLL a: SOLVENT, CONCENTRATION AND OXYGEN DEPENDENCE

Fluorescence lifetimes (τ_f) of chlorophyll a (Chi a ) have been measured by the single-photon-counting technique over a wide range of concentrations (˜10^-7˜10^-4 M ) in deoxygenated pyridine, diethyl ether, toluene and methanol. At pigment concentrations ˜1 μ M , reabsorption of fluorescence induces significant artifacts on measured values of τ_f which are dependent on detection wavelength and the specific geometry of the experiment. There is a clear dependence of τ_f on the nature and degree of solvation, including both coordination of the central magnesium and hydrogen-bonding of the solvent (viz. alcohols) to the macrocycle. Quenching of the excited singlet state by molecular oxygen was measured quantitatively in ether, and a bimolecular rate constant markedly slower than the diffusion-controlled limit was obtained.     

THE CORRELATION BETWEEN THE ABSORPTION AND THE FLUORESCENCE ENERGY SPECTRA,AND THE QUANTUM YIELD OF CHLOROPHYLL a IN DIFFERENT SOLVENTS†

Abstract— The applicability of Stepanov's relation to solutions of chlorophyll a in 17 solvents was determined. The value of T* (the local temperature of the excited molecules calculated by the relation) was higher than T (the ambient temperature) in 7 solvents and lower in one. The relative quantum yield determined by comparing the fluorescence spectrum with the thermal emission spectrum was fairly constant (? 1.0) up to 690 nm in dioxane, methylene chloride and dimethylformamide. In other solvents its value at 690 nm varied between 0.2 and 067. It is suggested that existence of a solute-solute or solute-solvent interaction in some solvents could possibly cause such a drop in the quantum yield.     

REASSESSMENT OF THE DIFFERENTIAL EFFECTS OF ULTRAVIOLET AND IONIZING RADIATION ON HIV PROMOTER: THE USE OF CELL SURVIVAL AS THE BASIS FOR COMPARISONS

Abstract: Effects of different radiation treatments on the human immunodeficiency virus-1 (HIV) promoter were reassessed for exposures comparable to those encountered in clinical or cosmetic practice, using survival of the host cell as a basis for comparisons. The exposures were performed with two ultraviolet radiation sources commonly used as medical or cosmetic devices (UVASUN 2000 and FS20 lamps), a germicidal (G15T8) lamp and an X-ray machine. The UVC component of the FS20 lamp was filtered out. The emission spectra of the lamps were determined. The characteristics of these sources allowed us to discriminate among effects of UVA1 (340–400 nm), UVB + UVA2 (280–340 nm) and UVC (254 nm) radiations. Effects of irradiation were ascertained using cultures of HeLa cells stably transfected with the HIV promoter linked to a reporter—chloramphenicol acetyl transferase—gene. The exposures used caused at least two logs of cell killing. In this cytotoxicity range, UVA1 or X radiations had no effect on the HIV promoter, whereas UVB + UVA2 or UVC radiations activated the HIV promoter in a fluence-dependent manner. Survivals following exposure to UVB + UVA2 or UVC radiation were (1) at the lowest measurable HIV promoter activation, 30 and 20%, respectively, (2) at one-half maximal activation, 6 and 3%, respectively and (3) at the maximal activation, 0.5 and 0.2%, respectively. The results suggest that, among the radiations studied, UVB is the most important modality from the viewpoint of its potential effects on HIV-infected individuals, since (1) UVA1 or X radiations have no effects on the HIV promoter, (2) human exposure to UVC radiation is infrequent and (3) human UVB exposure is very common.     

RESONANCE RAMAN SPECTRA OF THE II-CATION RADICALS OF COPPER, COBALT, AND NICKEL METHYLOCTAETHYLCHLORINS: VIBRATIONAL CHARACTERISTICS OF CHLOROPHYLL MODELS

Abstract— By using excitation at 363.8 nm, resonance Raman (RR) spectra were obtained for Cu(II), Co(II), and Ni(II) complexes of methyloctaethylchlorin (MeOEC) and their ir-cation radicals. Additionally, the Raman spectra of the Cu(II) derivatives of (rarcs-octaethylchlorin (r-OEC) were included for comparison. The alkyl-substituted CuMeOEC exhibits a Raman spectrum that is nearly identical to that of the simpler (-CuOEC in both the neutral and oxidized states. Unlike the latter species, the cation radical of CuMeOEC is immune to oxidative dehydrogenation to porphyrin, and this has facilitated vibrational characterization of the ring-oxidized species. This study aims to compare the vibrational characteristics in the 1450 to 1700 cm^-t region of the metallochlorin ir-cation radicals to those of the corresponding oxidized metalloporphyrins. We focus on two modes in the1500–1520 cm^-1 and1620–1650 cm^-1 region that are analogous to the v₃ and v₁₀ vibrations, respectively, in the metalloporphyrin analogs. These vibrational modes are clearly defined in all species and exhibit a strong core-size dependency in the porphyrin complexes. The core-size study as well as the frequency changes upon oxidation support the conclusion that the v₃-like vibration in the chlorin species features substantial C_bC_b in addition to C_aC_m stretching character. The v,₀-like mode of the chlorin macrocycle, on the other hand, displays characteristics that closely resembles that of the porphyrin analog; consequently, these vibrations are of predominantly C_aC_m stretching character in both cases.     

基体改进效应石墨炉原子吸收测定易挥发性元素砷、硒、碲、银、锑和铋

石墨炉原子吸收测定易挥发性痕量元素时,往往在原子化以前的灰化阶段即挥发损失以致分析结果偏低.同时又由于允许的灰化温度较低,样品中的基体不能驱尽,因此在原子化阶段产生严重的背景吸收.为消除这类干扰,文献报道采用基体改进技术,即在待测样品溶液中或在石墨炉中加入某种化学试剂,将待测元素转变为较稳定的化合物,从而有利于提高灰化温度,防止灰化损失和消除基体干扰.我们已应用微克量钯作为基体改进剂测定废水中痕量汞和海水中铅.