Determination of ni,zn and al in bronzes and brasses after determining cu-pb-sn-sb by controlled-potential electrolysis

A method is given, which allows nickel, zinc and aluminium to be determined in the solution remaining after the determination of copper, lead, tin and antimony by controlled-potential electrolysis. Nickel is precipitated by dimethylglyoxime, zinc is deposited by controlled-potential electrolysis and aluminium is precipitated first by oxine and then by ammonium benzoate.     

丙烷在金属铁表面还原NO的实验研究

在程序控温电加热水平陶瓷管反应器、N2气氛和模拟烟气气氛以及300~1 100℃时,对丙烷在金属铁表面还原NO的特性进行了实验研究,并且与相同条件下甲烷在金属铁表面脱硝的效率进行了对比。结果表明,丙烷在金属铁表面能够高效地还原NO。N2气氛中在500~900℃,丙烷在金属铁表面的脱硝效率高于相同含量的甲烷脱硝效率,900℃以上丙烷在金属铁表面的脱硝效率超过95%,并且与甲烷的脱硝效率差别很小。模拟烟气条件下,当过量空气系数SR1小于1.0时,温度超过900℃后丙烷在金属铁表面还原NO的效率能够达到90%以上,且有、无燃尽的情况下,NO的还原率相差不大。在相同的条件下,丙烷在金属铁表面的脱硝效率高于相同条件下甲烷的脱硝效率。SO2对丙烷在金属铁表面还原NO的效率影响很小,可以忽略。     

Oxidation of quinazoline and quinoxaline by xanthine oxidase and aldehyde oxidase

Quinazoline is oxidized by xanthine oxidase initially (and rapidly) to 4-hydroxyquinazoline which subsequently is oxidized more slowly to 2,4-dihydroxyquinazoline. Both oxidative reactions are inhibited strongly by allopurinol. Quinazoline is oxidized by aldehyde oxidase to 4-hydroxyquinazoline but within a short time (3–5 minutes) the reaction ceases; the proposal that cessation of reaction is due to product inhibition is rendered untenable by our observation that 4-hydroxyquinazoline is rapidly oxidized by aldehyde oxidase to 2,4-dihydroxyquinazoline. Preincubation of aldehyde oxidase with quinazoline results in complete inhibition of the ability of the enzyme to oxidize 4-hydroxyquinazoline and the standard substrate N-methylnicotinamide. It appears therefore that quinazoline is able to react with aldehyde oxidase and inactivate it. Quinoxaline and 2-hydroxyquinoxaline are not oxidized by xanthine oxidase but are converted by aldehyde oxidase to 2,3-dihydroxyquinoxaline; all oxidations mediated by aldehyde oxidase are inhibited completely by menadione.     

Au36(SPh)23 nanomolecules

A new core size protected completely by an aromatic thiol, Au(36)(SPh)(23), is synthesized and characterized by MALDI-TOF mass spectrometry and UV-visible spectroscopy. The synthesis involving core size changes is studied by MS, and the complete ligand coverage by aromatic thiol group is shown by NMR.     

有机化合物血卟啉及其衍生物被物理因素--超声激活机理研究

利用1,3-二苯基异苯并呋喃(DPBF)作为单线态氧捕获剂,研究了超声激活血卟啉的机理,通过用紫外-可见分光光度计测量了超声辐照配制好的血卟啉和DPBF溶液后的DPBF相对消耗量,表明了单线态氧的存在量．实验结果显示了DPBF的消耗量随超声照射时间和强度的增加而增加．从而支持了超声激活血卟啉产生单线态氧的说法．并提出了采用各向同性集光球把声致发光和声场分开的方法,进一步研究了是超声空化产生的荧光,还是高温热点激活血卟啉产生单线态氧．与白光对比结果表明,声致发光虽能使照相底版感光,但不足以激活血卟啉产生单线态氧．     

Chemisorption of hydrogen sulfide on lead sulfide

The hydrogen sulfide chemisorption on lead sulfide at 22–100°C is studied by static testing in a vacuum and by pulsed chromatography. It is established that H₂S is sorbed in reversible and irreversible forms and that the process is accompanied by the sample charging. Irreversibly sorbed hydrogen sulfide is removed by heating the sample in a vacuum or in an inert-gas stream at temperatures exceeding the adsorption temperature by 30–50°C.     

Analysis of sterols in vegetable oils using off-line SFC/capillary GC-MS

Summary The analysis of sterols in vegetable oils by off-line SFC followed by capillary GC-MS is described. The fractionation of the sterols from the complex oil matrix is achieved by SFC on aminopropyl silicagel in less than 8 minutes. Injection and collection of the sterol fraction is fully automated and time controlled. The sterols are analysed without derivatisation by capillary GC-MS. Identification is performed by full scan electron ionisation and quantitation is carried out by extracted ion chromatography at m/e 107, with cholesterol as internal standard. The analyses of the sterols from the sunflower oil and two olive oils illustrate the possibilities of the method.     

Synthesis of the glivocarcin-M aglycone

The synthesis of the agylcone of the antibiotic Gilvocardin-M by a sequential Meerwein Diels-Alder route is reported. The D-ring of the agylcone is attached by a halogen atom directed Meerwein arylation reaction and the A-ring is attached by a halogen atom directed Diels-Alder reaction. In the key step the directing chlorine atom is removed by a new thiophenylation reduction sequence.     

Spectrophotometric determination of tin in steel

A new spectrophotometric method for the determination of traces of tin in steel is presented. The tin is isolated by an acid sulfide separation and a double carbamate-chloroform extraction and then determined by a phenylfluorone method in which the selectivity is increased by the use of peroxide and oxalate as masking agents and the sensitivity is increased by extracting the colored tin compound into a small volume of MIBK for the spectrophotometric analysis.     

TiO2-Al2O3复合载体的比较研究

对用混胶法和共沉淀法分别制备的ＴｉＯ２－Ａｌ２Ｏ３复合载体（ＴｉＯ２含量为０．０８ｇ／ｇγ－Ａｌ２Ｏ３）进行了对比研究，采用的表征方法有ＸＲＤ，ＸＲＳ，ＬＲＳ等，得出的结论如下：两种载体均保持了γ－Ａｌ２Ｏ３的骨架结构，但ＴｉＯ２的分散状态不尽相同，混胶样品中ＴｉＯ２主要以表面富集的形式分散在γ－Ａｌ２Ｏ３表面，这有利于集二者的优点于一体，共沉淀样品中ＴｉＯ２趋于整个体相均匀分散，这有利于相互作用     

Problems encountered with the routine application of HPLC to the analysis of carbamate pesticides

Summary This paper describes the determination of all carbamate pesticides mentioned in the Austrian regulations for pesticides and of some other carbamates commonly used in the EEC. Clean-up procedure is carried out by ethyl acetate extraction. Purification is by a liquid-liquid extraction step followed by use of a florisil column. Final detection of the carbamates is carried out by HPLC on silica gel and GLC respectively The method works well for all carbamates under consideration. Only benzimidazolamine-2, the decomposition product of benomyl and carbendazime cannot be determined by the method described. Therefore determination of benomyl, carbendazime and benzimidazolamine-2 was by hydrolysis of benomyl and carbendazime to benzimidazolamine-2, which is then determined by reversed-phase chromatography.     

Fractal models of the shrinkage compensation mechanism for unsaturated polyesters

The shrinkage compensation mechanism in sheet molding compounds is governed by the morphology resulting from phase separation and microvoids formation. The observed microvoid morphology is quantified by using fractal geometry, in 2D and 3D spaces. The correlation between the morphologies of the matrix with phase separation and those of the microvoids is demonstrated by simulation. The pressure effect is studied. The fact that the shrinkage compensation has a pressure dependent optimum is explained by a model for the compensated volume. Thus, the “fractal pillar effect” is a model that represents properly speaking the compromise between pressure and volume creation shown by such a smart material.     

A computer program system — new chemics — for structure elucidation of organic compounds by spectral and other structural information

Computer-assisted structure elucidation is improved by the introduction of substructures selected by the user, in addition to analyses of the spectral data of an unknown organic compound. The substructure is called a 'macrocomponent' in the system. The macrocomponent which is input at will is authenticated by comparison with the set of components assembled by the automated analyses of the spectra before it is used for structure construction. It is shown that the introduction of the macrocomponent enhances the correctness and practicality of structure elucidation by computer.     

Determination of uranium,zirconium, magnesium and iron in bismuth alloys

Uranium in bismuth alloys is determined by a procedure where E.D.T.A. is added to complex bismuth and other metals and uranium oxinate is extracted by chloroform and determined spectrophotometrically. Zirconium is determined spectrophotometrically using alizarin S as reagent under carefully controlled conditions of acidity and time of colour formation. Magnesium is determined indirectly by measuring the absorption of oxine spectrophotometrically after precipitating the magnesium oxinate complex and redissolving. Bismuth is first separated by extraction of its iodide complex with methyl isobutyl ketone, and other interfering metals by extraction of their oxinate complexes at pH 6.5. Iron is determined as its thiocyanate complex after extraction with methyl isobutyl ketone, bismuth thiocyanate remaining in the aqueous phase.     

Monitoring of Fluorescent-Labelled Main Progesterone Metabolite in Marmoset Monkeys

Abstract

5α-pregnane-3α, 7α-diol-20-one, the main progesterone derivative in marmoset monkeys, shows a very low absorption in UV-light. Labelling of this metabolite prior to HPLC and subsequent monitoring by an UV-detector is essential. We used dansyl-hydrazine for the formation of a fluorescent derivative. The optimum conditions for the reaction of dansyl-hydrazone with hydroxypregnanolone were controlled by HPTLC, chromatographic separation is carried out by HPLC and HPTLC and is described in this paper. When the quantitation of the dansylhydrazones is carried out by HPTLC, the fluorescence intensity of the derivative can be increased by a factor up to 5 by dipping the HPTLC plate into a mixture of paraffin/n-hexane or after treatment with triethanolamin/isopropanol (1:4; by vol). Hydroxypregnanolone from marmoset urine is detected for the first time by liquid chromatography. The derivative is of practical use to determine ovulation and pregnancy in the marmoset monkey. Quantitation by HPLC and thin-layer chromatography is possible in the range of 10 to 1000 ng. The concentrations in marmoset urine during the luteal phase is in the range of 50 to 400 ng/mg creatinine.     

Chronocoulometric study of the electrochemistry of Prussian blue

During the electrochemical oxidation of Prussian blue (PB) to Prussian yellow (PY), an electrocatalytic oxygen production proceeds at the electrode when aqueous electrolyte solutions are used. The formed oxygen is scavenged by the PY, probably by absorption, and it is consumed during the electrochemical reduction of PY to PB by a heterogeneous chemical reaction of PB with oxygen to PY and hydrogen peroxide. Because of this catalytic regeneration of PY, it is impossible to determine the amount of low-spin iron by chronocoulometry using a potential program in which PB is first oxidized to PY and then the charge is measured to reduce PY to PB. The latter charge is biased by the electrocatalytic PY regeneration.     

几种建筑材料的氡射气系数研究

通过天然γ能谱测量方法测定建材样品中的镭含量,计算理论上衰变产生的氡密度,以及用硫化锌闪烁法测定由样品释放到空气中的氡密度的方法来计算氡的射气系数。通过改变样品的颗粒度大小,以及改变样品的灼烧温度等条件,来研究氡射气系数的变化规律。结果表明,土坯砖射气系数在8.5%~29.4%,红砖射气系数在0.031%~3.5%之间,瓷砖射气系数在0.74%~4.5%之间;建筑材料的氡射气系数随着其自身颗粒度的增大而减小,随加工(灼烧)温度升高而减小。     

Mechanism of action of a fire retardant chloroparaffin

The mechanism by which a typical fire retardant chloroparaffin imparts fire retardant characteristics to high density polyethylene, polypropylene and polystyrene is studied by comparing the oxygen indices of these mixtures measured before and after dehydrochlorination. It is shown that flame poisoning by HCl evolved from the chloroparaffin is negligible in polystyrene and high density polyethylene, whereas it is noticeable in polypropylene. The results obtained are related to previous data on the thermal degradation of these mixtures. It is concluded that the chloroparaffin acts mainly by modifying the mechanism of pyrolysis of these polymers in the burning process. Only in the case of polypropylene is there an appreciable contribution by flame poisoning.     

Back-electron transfer suppresses the periodic length dependence of DNA-mediated charge transport across adenine tracts

DNA-mediated charge transport (CT) is exquisitely sensitive to the integrity of the bridging pi-stack and is characterized by a shallow distance dependence. These properties are obscured by poor coupling between the donor/acceptor pair and the DNA bridge, or by convolution with other processes. Previously, we found a surprising periodic length dependence for the rate of DNA-mediated CT across adenine tracts monitored by 2-aminopurine fluorescence. Here we report a similar periodicity by monitoring N 2-cyclopropylguanosine decomposition by rhodium and anthraquinone photooxidants. Furthermore, we find that this periodicity is attenuated by consequent back-electron transfer (BET), as observed by direct comparison between sequences that allow and suppress BET. Thus, the periodicity can be controlled by engineering the extent of BET across the bridge. The periodic length dependence is not consistent with a periodicity predicted by molecular wire theory but is consistent with a model where multiples of four to five base pairs form an ideal CT-active length of a bridging adenine domain.     

Sol-Gel Carrier Systems for Controlled Drug Delivery

Embedding of the well-known coronary therapeuticum nifedipine into a modified silica matrix by the sol-gel technique allows its releasing behavior to be controlled to a high degree. The liberation rate is proportional to temperature and is increased by the addition of penetration agents such as sorbitol, but is inversely proportional to particle size and is decreased by modification of the silica matrix with methyl-triethoxysilane or polyethylene-glycol. It is presumed that the drug is dispersed in the gel matrix and that diffusion occurs through solvent-filled capillary channels. The liberation rate is governed by the relationship between the rates of dissolution and diffusion.