Determination of trace metals in industrial boron carbide by solid sampling optical emission spectrometry. Optimization of DC arc excitation (current, atmosphere and chemical modifier)

Graphite arc emission spectrometry has become possible as a result of the invention of novel types of optical spectrometers with Echelle-optics and semiconductor array detectors, and by the application of electronically controlled, high current arc generators. An optimization of the excitation parameters to boron carbide analysis is reported here, measuring background corrected line intensities that were integrated for the time of total evaporation of 5 mg boron carbide sample with or without added chemical modifiers. The following set of experimental conditions were compared with respect of analytical sensitivity and precision: (A) no modifier, Ar + O₂ (20%), 16 A; (B) sample + graphite powder (1 + 1), Ar + O₂ (20%), 16 A; (C) sample + CaF₂ (1 + 1), Ar, 25 A; (D) sample + CaF₂ + graphite powder (1 + 1 + 1), Ar, 25 A. The graphite powder modifier resulted in improved precision in general, and the CaF₂ was effective as a plasma ionization buffer and fluorinating agent. The best compromise was found under conditions B, when oxygen was present in the discharge atmosphere. This is likely due to the stepwise conversion of the boron carbide matrix to the more volatile boron oxide. Under conditions B, detection limits in the ranges of 0.3–9 μg g⁻¹ for Al, Ca, Cr, Cu, Fe, Mg, Mn and Si and that of 18–38 μg g⁻¹ for Ti, W, and Zr were attained. Average RSDs of 10.2 and 9.7% were found, respectively, without and with internal referencing to boron.     

New Dolabellane Derivatives from the Brown Alga Dictyota pardalis

Reinvestigation of the brown alga Dictyota pardalis f. pseudohamata CRIBB led to the crystallization of 1 and to the isolation of the two new dolabellane derivatives 2 and 3 . X-Ray analysis of 1 and 2 , together with detailed 1D-and 2D-NMR studies on 2 and 3 , allowed their structures to be elucidated as (1R*,3S*,7S*,11R*,4Z)-dolabella-4,8(17), 12(18)-triene-3,7-diol ( 1 ), (1R*,3S*,4S*,7S*,8S*,11R*,14R*,12E)-3,4:7,8-diepoxydolabe11-12-ene-14, 18-diol ( 2 ), and (1R*,3S*,4S*,7S*,8S*,11R*,14R*)-3,4:7,8-diepoxy-l,4,8,12,12-pentamethylbicyclo[9. 3. 0]tetra-decan-14-ol( 3 ).     

Veronicosid,ein neues Iridoidglucosid aus Veronica officinalisL.(Scrophulariaceae)

Veronicoside, a new iridoid glucoside from Veronica officinalis L. (Scrophulariaceae) A new iridoid glucoside, Veronicoside ( 1 ) has been isolated from Veronica officinalis L. The structure of 1 has been determined by chromatographic and spectroscopic analysis as 6-benzoylcatalpol.     

Untersuchung von AIIIB-Halbleitereinkristallen mittels Rutherford-Rückstreuung energiereicher Protonen

Axial blocking in various binary (GaAs, GaP, InSb, GaN) and ternary ((Ga, Al)P; (Ga, Al)As; (Ga, Al)Sb; (Ga, In)As) single crystals and epitaxial layers of the A^IIIB^V-type has been investigated by means of Rutherford backscattering with 0.5 MeV- and 1 MeV-protons. The angular distributions of the latter has been measured with solid-state detectors and with photographic plates. The observed “zero-depth” values of the blocking dips are in fair agreement with theoretical predictions by Barrett. Some applications of proton blocking and channeling to A^IIIB^V-compounds by backscattering are briefly described and some measuring examples are given.     

Rational Design of Macromolecular Structures: Focusing on the Embryonic Stages of Polymerization

Acetate-terminated oligomers of fluoral, chloral and bromal, prepared with the lithium alkoxides of tert-butanol and (-)-borneol, were analyzed by gas chromatography, polarimetry, NMR and mass spectroscopies, and by single crystal x-ray diffraction methods. The configurational and conformational properties of the “embryonic” adducts were found to depend strongly on the relative size of the trihalomethyl side group in these systems. The results of our efforts, summarized here, help to shed new light on the origins of helical geometry and crystalline order in polymers of the perhaloacetaldehydes.     

Oriental Lacquer. 10. The South East Asian Lacquer

Abstract

The family Anacardiaceae consists of 76 genera and about 600 species. A comparison of the species of Anacardiaceae is discussed with special emphasis on the importance of the exudates, the so-called sap, for their importance as lacquer to produce lacquer ware. Many exudates are poisonous. The individual chemical compounds which constitute the active ingredients of the oleoresin part of the sap and their function are described based on space-filling molecular models. Emphasis is also given to the organic components of lacquer trees of the South East Asian region, which is compared to other species of the Anacardiaceae family.     

Raman micro‐spectroscopy for quantitative thickness measurement of nanometer thin polymer films

The sensitivity of far‐field Raman micro‐spectroscopy was investigated to determine quantitatively the actual thickness of organic thin films. It is shown that the thickness of organic films can be quantitatively determined down to 3 nm with an error margin of 20% and down to 1.5 nm with an error margin of 100%. Raman imaging of thin‐film surfaces with a far‐field optical microscope establishes the distribution of a polymer with a lateral resolution of ~400 nm and the homogeneity of the film. Raman images are presented for spin‐coated thin films of polysulfone (PSU) with average thicknesses between 3 and 50 nm. In films with an average thickness of 43 nm, the variation in thickness was around 5% for PSU. In films with an average thickness of 3 nm for PSU, the detected thickness variation was 100%. Raman imaging was performed in minutes for a surface area of 900 µm². The results illustrate the ability of far‐field Raman microscopy as a sensitive method to quantitatively determine the thickness of thin films down to the nanometer range. Copyright © 2015 John Wiley & Sons, Ltd.