PVC塑料包装中化学物总迁移的研究

食品包装安全是食品安全的一个重要环节.食品容器、包装等接触材料与食品长期接触会发生"迁移",分为总迁移(overall migration)和特定迁移(specific migration)[1].其中,特定迁移是指某一特定物质在食品包装或容器与食品接触过程中发生的迁移;总迁移是从塑料材料或制品样品到试验媒介的组分总体迁移量.就物质而言,有可知物与未知物,就过程而言,有包装向食品的迁移,也有食品向包装的渗透、吸收等.进行总迁移实验有助于更全面了解一种材料与食品接触会发生的总体变化,对特定迁移的研究起有辅助与补充作用.欧盟对于食品模拟物、样品及前处理[2]、迁移测试方法[3]都有相应规定[4],本实验采用整体浸泡法,研究了PVC材料中化学物在不同食品模拟物中的总迁移.1 实验部分1.1 实验试剂和器材     

Isomerization of the hydrochlorides of some alkaloids of the matrine series

Conclusions The conversions of sophoridane into allomatridine and matridine, of isosophoridane into allomatridine, and of isosophoridine into sophoridine have been effected. A mechanism has been proposed for the thermal isomerization of the hydrochlorides of the quinolizidine alkaloids.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 2, pp. 96–99, 1969     

Basic Behavior of Epoxides in the Presence of Halide Ions

Epoxides behave as bases in the presence of catalytic quantities of halide ions. They convert halogenated hydrocarbons into olefins, suitable phosphonium salts into ylides, and haloforms into dihalocarbenes. Kinetic studies with the aid of JR and NMR spectroscopy show that the species that functions as the proton acceptor is neither the epoxide ion nor the halide ion, but the 2-haloethoxide ion.     

Encapsulation of Microbial Cells into Silica Gel

This work deals with changes in microbial phenol degradation and cell proliferation caused by immobilization into silica gel. Mixed microbial culture and the yeast Candida tropicalis were immobilized in silica layers and pieces prepared by mixing of prepolymerized tetraethoxysilane with cell suspension. The phenol degradation rate of cells entrapped in silica gel was compared with those immobilized into an organic polymer-polyurethane. The phenol degradation efficiency decreased in the following order: free cell suspension > cells entrapped into polyurethane foam > cells entrapped into prepolymerized TEOS. Inside the silica there was no growth observed by optical microscope. The immobilization of bacterium Pseudomonas species 2 into silica gel, cells which co-metabolize PCBs with biphenyl, did not result in substantial change of intermediate concentration.     

Application of the Sublattice Method to Analysis of the Chemical Bond in the Peroxides of Alkali Metals

Self-consistent calculations of the valence electron density and the sublattice and difference densities of alkali metal peroxides were carried out. It was established that the oxygen atoms in potassium, sodium, and rubidium peroxides are grouped into pairs, linked into chains by common valence density contours. In lithium peroxide the oxygen pairs are linked into chains through the lithium atoms.     

Transformations of cycloalkanes under the action of organoaluminum compounds and transition metal complexes in the presence of polychloromethanes

A catalytic system comprising an organoaluminum compound, polychloromethane, and a transition metal complex transforms cyclohexane into dimethyldecalins, cyclooctane into dimethyl- and ethylcyclohexanes, and endo-tricyclo[5.2.1.0^2,6]decane into its exo-isomer under mild conditions.     

Single enantiomer epoxides by bromomandelation of prochiral alkenes

A combination of mandelic acid and N-bromosuccinimide efficiently converts prochiral alkenes into a readily separable 1:1 mixture of the bromomandelates. The diastereomerically pure bromomandelates are then converted into a variety of enantiomerically pure products. Terminal alkenes are converted into enantiomerically pure epoxides. Cyclohexene is converted into enantiomerically pure cis-2-azidocyclohexanol and cis-2-phenylthiocyclohexanol.     

Chemoenzymatic Synthesis of Advanced Intermediates for Formal Total Syntheses of Tetrodotoxin

Advanced intermediates for the syntheses of tetrodotoxin reported by the groups of Fukuyama, Alonso, and Sato were prepared. Key steps include the toluene dioxygenase mediated dihydroxylation of either iodobenzene or benzyl acetate. The resulting diene diols were transformed into Fukuyama's intermediate in six steps, into Alonso's intermediate in nine steps, and into Sato's intermediate in ten steps.     

Reactivity of a Stable Phosphinonitrene towards Small Molecules

The room‐temperature stable phosphinonitrene 1 undergoes a thermal rearrangement into heterocycle 2 through a process involving a nitrene insertion into a CH bond. In the presence of acetonitrile, a nitrene–acetonitrile adduct has been isolated; then it first rearranges into a ketenimine and subsequently into a rare example of diazaphosphete. Compound 1 also splits water, carbon dioxide, carbon disulfide, and elemental sulfur, although it reacts with white phosphorus, leading to a P₅N cluster formally resulting from the insertion of the PN moiety into a P?P edge of the P₄ tetrahedron.     

Transformations of gossypol in low-molecular-mass alcohols

It has been shown that the transformations of gossypol into anhydro derivatives on its storage in methanol, ethanol, and propanol take place the faster the lower the molecular mass of the alcohol and the higher the temperature of the process. It has been established that when alcoholic solutions of gossypol in methanol are heated it is converted completely into dianhydrogossypol, in propanol into monoanhydrogossypol, and in ethanol into a mixture of equal amounts of mono- and dianhydro derivatives.     

Role of acidity on the electrochemistry of Prussian Blue at plain and Nation filmcoated electrodes

Prussian Blue (PB) coated on plain platinum (Pt) shows a redox wave at 0.44V vs SCE in addition to the two usual redox waves at 0.82 and 0.12 V vs SCE when the electrodes were dipped in acidic KC1 solution. PB incorporated into Nation film-coated on Pt electrode exhibited the same behaviour even in the presence of neutral KG solution. In acidic KC1, the additional redox wave observed for PB incorporated into Nation film shifted positively to 0.39V vs SCE and the peak separation was reduced to 30mV. The observed additional redox wave for PB coated on plain Pt electrode and incorporated into Nafion film-coated Pt electrodes was assigned to the partial reduction of PB occurring due to the insertion of protons into the film. The effect of various cations on the electrochemistry of PB incorporated into Nafion film-coated electrode was also studied.     

Unexpected remarkable stability of primary ozonides derived from alkenyl stannanes. One-pot synthesis of 1,2-diols from alkynes

Primary ozonides derived from alkenyl stannanes display an unusual stability and can be transformed into 1,2-diols by treatment with dimethyl sulfide and borane-methyl sulfide complex. This observation has been incorporated into the development of a novel one-pot strategy for the conversion of alkynes into 1,2-diols.     

双刚性共轭嵌段共聚物体系的自组装

棒杆-棒杆(rod-rod)共轭嵌段共聚物体系是近几年发展起来的一类新型共轭聚合物材料,由于其特有的电学活性以及通过自组装实现纳米尺度结构可控等特性正逐渐成为人们研究的热点.构筑单元的刚性棒状结构使得rod-rod共轭嵌段共聚物体系倾向于自组装形成囊泡或层状结构等低曲率聚集体.本文总结了近年来关于rod-rod共轭嵌段共聚物体系自组装行为的研究,分别介绍了溶液中以及薄膜状态下双刚性共轭嵌段共聚物体系的自组装行为,在此基础上进一步讨论了rod-rod共轭嵌段共聚物薄膜结构与性能的关系.     

Spectral study of the conversion of porphyrins during interaction with molecular negative ions

In the interaction of ethioporphyrin and of several of its metal derivatives with negative ions of pyridine and anthracene in tetrahydrofuran solutions, an electron transfer takes place which results in the conversion of the pyridine and anthracene ions into neutral molecules, whereas the molecules of the pigment are first transformed into monovalent anions and subsequently into the di-, tri-, tetra-, and sometimes even into the hexavalent anions. In the first stage of this interaction, ferriethioporphyrin is reduced to ferro-ethioporphyrin, whereas the unmetallized pigment and its copper complex are transformed into the disodium derivative of ethioporphyrin. When the temperature is lowered, the rate of the electron transfer from pyridine ions to zinc-ethioporphyrin is decreased, and illumination leads to a substantial rate increase. The photochemical sensitivity of this system is possibly linked to the formation of stable complexes between pigment molecules and pyridine ions.     

颗粒流体系统的非线性行为

该文讨论颖粒流体系统的研究现状和可能的发展方向。认为非线性行为是实现颖粒流体系统定量化的难点所在,它可分为来源于颖粒流体相互作用的内在非线性和来源于外界影响和非理想物性的次生非线性。内在非线性引起系统内的自组织现象、分支现象和混沌运动,次生非线性则使得内在非线性的分析更加复杂。提出了认识非线性行为的两种可能途径:(1)把系统进行多方面的分解,即运动分解为极值和动态,能耗分解为可逆和耗散,过程分解为有序和无序,结构分解为不同尺度;(2)将该系统处理为尺度差别很大的两种介质的相互作用并进行计算机图形仿真。     

The dynamics of the accumulation of the alkaloids of the genus Ungernia

Summary A study ofU. victoris, U. tadshicorum, andU. trisphaera with respect to the vegetation periods and growth sites has shown that the maximum accumulation of alkaloids takes place in the early vegetation period and that naturally dried leaves do not contain alkaloids. The alkaloid content also depends on the growth site.In the period of the vigorous development of the epigeal part, some alkaloids are possibly converted into one another (hippeastrine into lycorine, galanthamine into narwedine, and narwedine into galanthamine).Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 60–64, January, 1971.     

Modification of films of heat-resistant polyimides by adding hydrosilicate and carbon nanoparticles of various geometries

The possibility of modifying the properties of poly(4,4′-oxydiphenylene)pyromellitimide films by introducing into prepolymer solutions nanoparticles of various compositions and structures [hydrosilicate nanoparticles in the form of layered structures (montmorillonite) and nanotubes; carbon nanofibers] was examined. New intercalating agents, tetranuclear aromatic diamines, were suggested for pretreatment of montmorillonite prior to introduction into heat-resistant polymers. The mechanical characteristics of the nanocomposites with hydrosilicate nanotubes can be optimized by chemical pretreatment of the nanotubes prior to introduction into the polymer matrix. Introduction of the above-named nanoparticles into the polymer matrix appreciably increases the elastic modulus of the material. The largest increase in the elastic modulus is observed with hydrosilicate nanotubes of the chrysotile structure, coated with an aromatic modifier.     

The Photochemistry of Diazomethane the Reactions of Methylene with Methanol and Ethanol

In the photolysis of diazomethane-methanol. mixture, the reaction of methylene with methanol gives dimethyl ether and ethanol as products. The ratio of dimethyl ether to ethanol is found to be independent to pressure and to. the composition of diazomethane-methanol mixture. Methylene insertion into O—H bond is about 11 times faster than that into C—H bonds of methanol. The ratio decreases with increase of temperature. In the diazomethane-ethanol system, ethylmethyl ether, propanol-1 and propanol-2 are found as the products of insertion reaction of methylene into ethanol. The ratios of ethylmethyl ether to propanol-1 and to propanol-2 are both found to be almost constant and independent to pressure and to the composition of diazomethane-ethanol mixture. A small temperature effect on the ratios are observed. The rate of insertion of methylene into O—H bond is about 7.3 and 14.2 times faster than those into primary and secondary C—H bonds of ethanol, respectively.     

不同进气方式对热等离子体应用于CH4-CO2重整的影响

采用大功率双阳极热等离子体装置, 对CH4-CO2重整制合成气进行实验研究. 实验采用两种不同的原料气输入方式: 一种是使原料气(CH4和CO2的混合气体)作为等离子体放电气体全部通入第1阳极与第2阳极间的放电区, 直接参与放电; 另一种是保持前述状态, 再附加另一部分原料气通入从等离子体发生器喷出的等离子体射流区. 实验表明: 第1种方式下, CH4和CO2同时具有很高的单程转化率和反应选择性, 但能量转化效率较低; 第2种方式下, 尽管CH4和CO2单程转化率和选择性有所降低, 但由于进料量增加, 所得合成气摩尔量较大, 因此能量转化效率高于第1种进气方式所得结果. 实验还发现, 保持放电电流恒定的情况下, 等离子体放电电压随通入第1阳极与第2阳极间放电区的原料气流量增加而增加, 与通入等离子体射流区的流量无关, 同时实验未发现等离子体发生器阴极和阳极被氧化或出现碳沉积现象.     

微波条件下双酚A向食品模拟物的迁移研究

采用气相色谱-质谱联用法研究了微波条件对食品接触材料中双酚A在水、乙酸（3%,体积分数）、乙醇（10%,体积分数）、橄榄油4种食品模拟物中迁移行为的影响。在微波加热下,食品快速升温并能将热量传递给外部包装,从而加速包装材料中双酚A向食品的迁移。研究了不同微波温度、时间和功率下双酚A在4种食品模拟物中的迁移规律,结果表明：微波对双酚A迁移有显著影响,迁移量随着微波温度、时间和功率的增加而增加。在相同加热温度和时间条件下,微波加热方式中双酚A在4种食品模拟物种的迁移量均高于水浴加热。