Half a Century of Polystyrene—A Survey of the Chemistry and Physics of a Pioneering Material

Hermann Staudinger, the founder of polymer chemistry, would have been 100 years old this year. One of the key materials with which he elucidated the structure of high polymers was polystyrene.—Polystyrene, one of the most important thermoplastics, has now been manufactured industrially for some 50 years. Not only has it simplified our daily lives in a variety of ways, it has also been a model substance for the development and expansion of polymer chemistry and polymer physics, and it was the pioneering material for handling polymer solutions and melts. This article surveys the development and present state of knowledge of the polymerization of styrene and of the relationships between structure and properties.     

“… to make Chemistry more Applicable and Generally Beneficial”—The Transition in Scientific Perspective in Eighteenth Century Chemistry

In 1751, the Swedish chemist Johan Gottschalk Wallerius first differentiated between “pure” and “applied” chemistry, a distinction which was quickly adopted by the other branches of science. Behind this was a new scientific concept of chemistry which emphasized the importance of applying chemistry's accumulated knowledge and its capabilities of providing for the general economic benefit. It also provided chemistry with a new position within the hierarchy of the sciences as well as with a new function in society. The reasons behind and causes of the change in scientific perspective associated with this concept point to the social and institutional conditions under which this field has developed into an independent academic discipline.     

益脑宁痫片中苯巴比妥的薄层色谱-紫外分光光度测定法

用薄层色谱法和紫外分光光度法分离和测定益脑宁痫片中苯巴比妥的含量。样品用氯仿-异丙醇-25％氨水溶液(45:45:10)为展开剂在硅胶GF_(254)板上展开后,将在紫外灯(λ=254nm)下显示分离的被测组分刮下,溶于0.1mol/L NaOH溶液中,在λ=255±1nm处测其吸收度,求得苯巴比妥含量。     

A Hundred Years of Stereochemistry—The Principal Development Phases in Retrospect

The theory of the arrangement of atoms in space was initiated in 1874 by van't Hoff and Le Bel. The starting points were mainly in the fields of structural chemistry and optical activity. After early difficulties, stereochemistry gained acceptance in the last quarter of the 19th century and led to many interesting investigations and discoveries: the investigation of geometrical isomerism, the Baeyer strain theory, the stereochemistry of nitrogen, the determination of the configurations of carbohydrates, Walden inversion, and the beginning of inorganic stereochemistry all fall in this period. Theoretical verification of the principal stereochemical hypotheses and the exact determination of the steric arrangement of atoms by physical methods were achieved only in the 20th century.     

Chemistry for the Future—State of the Art and Perspectives

A particularly close relationship exists between chemistry, the science of the transformation of matter, and developments in human living conditions. Though little more than 150 years old, chemical technology has had a greater influence on our civilization than any other technological discipline. Its roots lie not in the crafts, but in scientific research. Relationships derived from the laws of nature were taken as a basis for the systematic solution of practical problems. It is to this strategy that chemistry owes its success. New opportunities arise from new discoveries. These result from basic research at universities, research institutes, and industrial laboratories. Applied research in turn transforms the discoveries into innovative solutions to problems on an industrial scale. The objectives of applied research are oriented toward the marketplace and to the needs of mankind. Our knowledge of scientific interrelationships has been growing with unabated vigor for decades, but so too has our insight into the enormous complexity of the material world. Many of the problems that civilization faces result from the fact that our knowledge is still inadequate. Intensive research and development offer the only hope for progress. Scientists must of course act responsibly with the knowledge they acquire, and they must provide the information necessary to establish public confidence in their methods and products. This is the prerequisite for broad acceptance of technological progress, and given the extent of the world's population no alternative to progress exists. The shape of that progress is also subject to influences outside the realm of science, however, including social norms and political activities. A country that is not rich in raw materials, like the Federal Republic of Germany, must pay particular attention to these factors as well if it is to maintain its innovative strength.     

August Wilhelm Hofmann—“Reigning Chemist-in-Chief”

One hundred and twenty-five years ago, on November 11th, 1867, the German Chemical Society of Berlin held its inaugural meeting. The main purpose of the Society was to unite pure and applied chemistry and to foster cooperation between academic research and the chemical industry. And, indeed, it soon became the major forum of German and even European chemistry. Its program clearly bears the hallmark of a single individual: August Wilhelm Hofmann, the Society's first president, who died 100 years ago. For his contemporaries, Hofmann represented a new type of chemistry professor. At no time since have professional chemists felt as abundantly endowed with potential for the future and with public esteem. Hofmann's portrait was monumental even then, and still today it would belong in any gallery devoted to our distinguished forebears. Anniversaries provide an opportunity to direct our attention toward the past—and thus to ourselves as well. We are, after all, heirs to that period from which the modern world derives its profile. Questions from our own time lead us to reacquaint ourselves with one of the founders of modern chemistry, but we may also benefit from a fresh look at an epoch which, beneath the surface of prosperity and progress, was as contradictory as our own, an epoch struggling to understand the role of science in the new industrial era.     

Evaluation of the lipophilicity of selected sunscreens—A chemometric analysis of thin‐layer chromatographic retention data

The lipophilicities of 22 selected sunscreens, preservatives, and vitamins used in topical skin products were measured by thin‐layer chromatography. Lipophilicity was calculated in silico from the sunscreen molecular structures and compared to the experimental octanol/water partition coefficients found in the literature. The retention of the compounds was investigated on an RP‐18 stationary phase with mobile phases consisting of water and one of six organic modifiers (dioxane, tetrahydrofuran, acetone, acetonitrile, methanol, and dimethylformamide) at different concentrations. The theoretical lipophilicities were calculated by several computational algorithms and the results of these calculations were compared using cluster analysis. The results showed that two out of the six investigated organic modifiers (dioxane and acetone) may be used to estimate the octanol/water partition coefficients of highly lipophilic compounds having lipophilicities that cannot be measured directly by the shake‐flask method.     

Rapid Preparation and Easy Quality Control Procedures for 99mTc‐Tin‐Nano Colloid: A Lymphoscintigraphic Agent

^99mTc‐Tin‐nano colloid is a radiopharmaceutical that can be useful in evaluation of the patients with breast cancer. The current method for preparation requires a lengthy boiling water bath procedure, and the recommended quality control procedure is cumbersome and time consuming. Using a microwave oven, the heating time necessary to provide a maximum labeling efficiency has been reduced to 10 second. A new mini paper chromatography (MPC) system has been developed to analyze the radiochemical purity (RCP) of the labeled preparation involving two different developing solvents. The recommended thin layer chromatography (TLC) system involving the use of an Al₂O₃ coated plate requires an average time for drying and development of 34.5 ± 0.44 min (n = 30) to complete, whereas the new MPC system has an average developing time of 2.1 ± 0.2 min (n = 20). For RCP values the MPC and TLC methods are correlated closely (r = 0.94). The combined use of the microwave oven heating method and over quick quality control system will facilitate the rapid emergency use of ^99mTc‐Tin‐nano colloid.     

蔗糖酯的薄层分析

 以硅胶G板为固定相、甲苯 乙酸乙酯 甲醇 水 (体积比为 1 0∶5∶4 5∶0 2 )为流动相 ,研究建立了蔗糖酯薄层分析方法。在蔗糖酯上行展开后 ,用脲 磷酸 水饱和正丁醇溶液显色 ,斑点呈蓝色 ,蔗糖单酯的Rf 值为 0 1 6 ,多酯的Rf 值为 0 38～ 0 93。在 70℃显色 2 0min的最佳条件下 ,蔗糖单酯的检测量为 2 5 μg～ 2 50 μg时 ,其斑点面积与其检测量有良好的线性关系。用归一法和外标法对该分析方法的准确度进行考察和认证 ,两种方法对已知单酯含量的S 1 570样品测定结果的t 检验结果分别为 |t| =0 62 7(<2 571 )和 |t|=1 1 2 3(<2 571 ) 。     

Thin‐layer chromatography—an image‐processing method for the determination of acidic catecholamine metabolites

A sensitive and convenient method for acidic catecholamine metabolites (including homovanillic acid, vanillylmandelic acid, 3,4‐dihydroxymandelic acid, and 3,4‐dihydroxyphenylacetic acid) determination was developed based on thin‐layer chromatography and image‐processing analysis. The metabolites were separated without a prederivatization step using reversed phase RP‐18W high‐performance plates. The mobile phase composition, detection, and quantification conditions were systematically investigated through several trials. The reaction with 2,2‐diphenyl‐1‐picrylhydrazyl radical allowed specific detection of acidic catecholamine metabolites with a high sensitivity and a wide linear range. The limit of detection and the limit of quantification were in the range of 13–103 and 18–120 ng/spot, respectively, in all cases. Mean recoveries determined were in the range 95–106% for all of the investigated compounds. The proposed method allowed rapid simultaneous determination of acidic catecholamine metabolites from spiked human urine sample.     

Liquid Chromatography—Its Development and Key Role in Life Science Applications

Liquid chromatographic methods cover the broadest range of applications imaginable today. Nowhere is this more evident and relevant than in the life sciences, where identification of target substances relevant in disease mechanisms is performed down to the femtomole level. On the other hand, purification of therapeutic drugs on a multi‐ton scale is performed by process LC. The complexity and abundance range of biological systems in combination with the extreme purity requirements for drug manufacturing are the challenges that can be mastered today by chromatography, after more than a century of research and development. However, significant improvement is still required for a better understanding of the scientific fundamentals of the underlying phenomena and exploiting those for an enhanced quality of live.     

Dendrimers: From Design to Application—A Progress Report

A unique combination of a clearly defined particle structure and a very highly functionalized surface is offered by the topical dendrimers. Many groups work on this unusual molecular architecture to develop new applications. The most advanced progress in this respect is an MRI contrast agent based on dendrimers (see schematic representation) that facilitate the visualization of bloodstreams.     

August Kekulé—The Architect of Chemistry Commemorating the 150th Anniversary of His Birth

Imagination, daring, and critical understanding are the sources of the impulses still felt today which chemistry received from the theoretical studies of Kekulé. “Let us learn to dream, gentlemen, then perhaps we shall discover the truth; but let us beware of publishing our dreams abroad before they have been scrutenized by our vigilant intellect … Let us always allow the fruit to hang until it is ripe. Unripe fruit brings even the grower but little profit; it damages the health of those who consume it; it endangers particularly the youth which cannot yet distinguish between ripe and unripe.” (Kekulé 1890).     

N-二氯乙酰基噁唑烷合成反应的薄层色谱法研究

用薄层色谱法监测了用二氯乙酰氯、醇胺和酮合成的除草剂的安全剂N 二氯乙酰基 口恶唑烷的反应过程。方法操作简便、快速、准确。     

Lise Meitner: Her Life and Times—On the Centenary of the Great Scientist's Birth

Cooperation between the three scientists Lise Meitner, Otto Hahn, and Fritz Strassmann in the study of the “transuranics” (1934—1938) prepared the way for the chemical identification of a first fission product of uranium by Otto Hahn and Fritz Strassmann at the end of 1938. Together with her nephew Otto Robert Frisch, she also gave the first theoretical interpretation of that experimental finding (barium instead of the expected radium) and suggested the inert gas krypton to be the second fission products, which Hahn and Strassmann subsequently identified (besides xenon) among the products. But she was kept from direct participation in the experiments conducted at the Kaiser Wilhelm Institute for Chemistry at Berlin—and therefore from the unrestricted claim to being co-discoverer of uranium fission—because she was an Austrian “Jewess”. Thus after the “annexation” of Austria by the German Reich, the Nazi racial laws also applied to her and precluded her continuing to work in Germany. She therefore emigrated illegally via Holland to Sweden in the middle of 1938. There she continued to work on problems of nuclear physics under less favorable conditions untill 1960. Work on radioactivity already started at Vienna had also brought her together with Hahn at Berlin in 1907, and she continued the work at the Kaiser Wilhelm Institute studying α-, β-, and γ-radiation and related nuclear processes. Not only because of her descent, but also because of her status of a woman in science, her fate was molded by the circumstances prevailing in Germany prior to World War II. On November 7, 1978 Lise Meitner would have celebrated her hundredth birthday, reason enough for recalling her lot as a woman scientist in Germany against the background of her times, which should stand as a warning to us. To that end contemporary documents could be quoted which till now were largely unknown.     

AB-8型大孔树脂分离提纯葛根素的研究

采用AB-8型大孔树脂对纯化葛根素的分离条件进行了研究,分别采用HPLC和薄层层析法研究了大孔树脂从葛根素粗品中分离葛根素的条件及影响因素。结果表明：采用AB-8型大孔树脂分离葛根素能够获得良好的分离效果。用大孔树脂分离葛根素具有操作简单、分离效果好等优点。