Iodine determination in biological materials Options for sample preparation and final determination

This paper describes the development of various new acid sample decomposition methods, as well as an extraction (leaching) method and compares them with the “Sch?niger Combustion” technique. The methods have been developed as sample preparation techniques for iodine determination in biological materials, especially in solid samples. ICP-MS (inductively coupled plasma mass spectrometry) and a catalytic technique are employed and discussed for the final determination of iodine concentrations. Accuracy and reliability of the different analytical methods are shown in the examples of different CRMs (certified reference materials) available for iodine. The results of an interlaboratory comparison are specifically presented for the extraction (leaching) method. Received: 11 May 1998 / Revised: 14 June 1998 / Accepted: 16 June 1998     

Bi4V2O11/石墨烯异质结光催化剂的制备及其在降解抗体污染物中应用

发展和设计高效、廉价和稳定的光催化剂用于抗生素污染物降解仍然存在巨大的挑战。 本文通过一种便捷的水热方法制备了Bi₄V₂O₁₁/石墨烯复合材料并用于可见光下抗生素污染物光催化降解。 通过自由基追踪实验,确认了光催化降解过程中活性物质为h⁺和·OH基团。 根据实验结果,提出了相应的反应机理。 石墨烯的引入可以有效地促进光生电子-空穴对的分离,从而增强光催化活性。 该复合催化剂展现出良好的活性和稳定性。 该方法以石墨烯为载体制备了光催化降解材料,为高性能光催化剂的制备提供了参考。     

Lewis碱改性氧化锆基质色谱固定相的研究进展

综述了Lewis碱改性氧化锆(或其复合氧化物)基质高效液相色谱填料的研究进展,涉及的改性剂包括氟离子、磷酸盐、有机膦酸、羧酸、酚类化合物、蛋白质和环糊精衍生物等。简要介绍了Lewis碱改性氧化锆固定相在毛细管电色谱中的应用。 引用文献51篇。     

β-环糊精键合改性介孔硅胶的表征和吸附性能评价

β-环糊精键合改性介孔硅胶的表征和吸附性能评价;酚类化合物     

强激光装置中玻璃疵病在线检测的光学系统设计

介绍了一种用于玻璃疵病在线检测的近摄工作距成像光学系统,其光组结构形式采用了光阑后置的准远心结构形式,主要光学参量为f′=14 mm;在物像距为250 mm约束条件下,物方视场达到90 mm（对角线）;F/number=3.56;光谱适应范围为400~800 nm,对应的空间分辨率为100 lp/mm时,调制传递函数大于0.29.     

荞麦花多糖的提取及含量测定

采用热水提取、乙醇沉淀的方法从荞麦花中提取出了水溶性多糖,采用硫酸-苯酚法在波长为497nm处进行了糖含量的测定,求得其校准曲线的回归方程为y=0.00508x 0.0294,相关系数为r=0.9978.平均回收率为99%-103%,RSD为0.74%.结果显示:荞麦花多糖的产率为2.5%.糖含量为41.63%.     

The rapid uncertainty prediction of the ocean-acoustic coupled model

Focusing on the rapid prediction of acoustic field uncertainty in environment with temporal and spatial sound speed perturbation, evolvement of sound speed structure over time is predicted based on the ocean-acoustic coupled model to obtain the uncertainty distribution of the vertical structure of sound speed. Further, a method combining the arbitrary polynomial chaos expansion with the empirical orthogonal function is proposed to reduce the dimensionality of uncertain parameters and to obtain the uncertainty distribution of the acoustic field. Simulations have shown that the computational complexity can be reduced by 2 orders of magnitude compared to the conventional polynomial chaos expansion while ensures the same precision.Moreover, the computational complexity is not influenced by the complexity of the sound speed profile. The acoustic field and uncertainty predicted in uncertain environment by proposed method also have been tested with the experimental data.     

3,4-Dihydroxy-7,8-dihydro-beta-ionone 3-O-beta-D-glucopyranoside and other glycosidic constituents from apple leaves

3,4-Dihydroxy-7,8-dihydro-beta-ionone 3-O-beta-D-glucopyranoside 1 has been isolated from a methanolic extract of apple (Malus domestica) leaves by XAD-2 adsorption chromatography and subsequent purification by high speed countercurrent chromatography (HSCCC) and HPLC. Under acidic conditions this glycoside gives rise to a number of volatile compounds including 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) 2, which is known as an off-flavor compound in wine. In the course of the study, six additional glycoconjugates were isolated from apple leaves, i.e. roseoside 3, 3-oxo-alpha-ionol beta-D-glucopyranoside 4, benzoic acid beta-D-glucose ester 5, kaempferol 3-O-rhamnoside 6, (+)-syringaresinol beta-D-glucopyranoside 7 and 4-hydroxy-5-(3'-methyl-2'-butenyl)-benzoic acid methylester 3-beta-D-glucopyranoside 8. The latter compound has been isolated for the first time in nature. In order to avoid the 'kerosene-off-flavor' caused by TDN, the methanolic extract has been subjected to yeast fermentation. This treatment reduced the amount of TDN formed and resulted in an improved flavor impression of the methanolic extract.     

A partially mechanized system for the combustion of organic samples in a stream of oxygen with quantitative recovery of the trace elements

Summary A partially mechanized apparatus made of quartz (Trace-0-Mat) is described that permits the complete mineralization of up to 1 g of organic or biological solid samples. The combustion takes place in pure oxygen in a very small burning chamber (ca. 75 cm³) to subsequently determine metallic and nonmetallic trace elements (1 ng/g) with high reliability. The controllable incineration is started with an IR-radiator system. All volatile trace elements (e.g. Hg, Se, Te, As, Sb, I) are condensed together with the products of the combustion process in a cooling system filled with liquid nitrogen that is mounted on top of the burning chamber. Subsequent refluxing with a suitable acid in a quartz test tube mounted below the burning chamber collects both the volatilized elements from the cooled areas and nonvolatile elements in the ashing residue. The volume of the acid is about 2 ml.The recoveries of the elements following the decomposition process that takes 50–60 min for one sample was checked using 7 NBS-Standard Reference Materials for the elements B, Cr, Cu, Fe, Mn, Zn (ICP-emission spectrometry), Cd, Pb (ETA-AAS), Hg (AAS-cold vapor technique), As (AAS-hydride method) and Se (XRF). Very good agreement with the certified values was observed. This furnished evidence that this new and very general decomposition method is not only poor in blanks but also avoids substantially losses of the elements to be determined by volatilization, adsorption or even baking in the quartz surface. The easy handling of the apparatus offers the best premises for a reliable determination of trace elements in the g/g and ng/g range in most non-volatile organic matrices.

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Teilmechanisiertes System zur Verbrennung organischer Proben im Sauerstoffstrom mit quantitativer Wiedergewinnung der Spurenelemente

Zusammenfassung Ein teilmechanisiertes aus Quarz bestehendes System (Trace-0-Mat) wird beschrieben, das die vollständige Mineralisation fester organischer oder biologischer Proben bis zu Mengen von 1 g gestattet. Die Verbrennung findet dabei in reinem Sauerstoff in einer sehr kleinen Verbrennungskammer (etwa 75 cm³) statt, so daß anschließend die metallischen und nichtmetallischen Spurenelemente mit hoher Zuverlässigkeit bestimmt werden können. Die steuerbare Veraschung wird durch ein System von IR-Strahlern gestartet. Alle flüchtigen Spurenelemente (z. B. Hg, Se, Te, As, Sb, I) werden zusammen mit den Verbrennungsprodukten in einem Kühlsystem kondensiert, das mit flüssigem Stickstoff gefüllt und über der Verbrennungskammer angeordnet ist. Die sich an den gekühlten Flächen befindlichen flüchtigen sowie die in der Asche vorhandenen nichtflüchtigen Elemente werden durch Rückflußbehandlung mit einer kleinen Säuremenge (2 ml) gelöst und in einem Quarzglas unterhalb der Verbrennungskammer gesammelt.Die Wiederfindung der Elemente nach dem Aufschlußprozeß (50–60 min) wurde mit Hilfe von 7 NBS-Referenzmaterialien für folgende Elemente geprüft: B, Cr, Cu, Fe, Mn, Zn (ICP-Emissionsspektrometrie), Cd, Pb (ETA-AAS), Hg (AAS-Kaltdampftechnik), As (AAS-Hydridmethode) und Se (Röntgenfluorescenz). Es ergab sich sehr gute Übereinstimmung mit den zertifizierten Werten. Diese neue und sehr allgemein anwendbare Aufschlußmethode weist nicht nur geringe Blindwerte auf, sondern vermeidet auch wesentliche Verluste der zu bestimmenden Elemente durch Verflüchtigung, Adsorption oder Zusammenbacken an der Quarzoberfläche. Durch die einfache Handhabung der Apparatur ist eine zuverlässige Bestimmung von Spurenelementen im g/g- und ng/g-Bereich für die meisten nichtflüchtigen organischen Matrices gewährleistet.