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Benzo(a)pyrene, Liquid-liquid partition, Microcrystalline waxes, Solid-phase microextraction, Aromatic hydrocarbons, Chromatography, Compliance control, Food additives, Gas chromatography, Hydrocarbons, Liquids, Mass spectrometry, Nobelium, Polycyclic aromatic hydrocarbons, Protective coatings, Pyrene, Solvent extraction, Spectrometry, Surface treatment, Analytical determination, Chemical specifications, Microcrystalline wax, Spectrophotometric detection, Total polycyclic aromatic hydrocarbons, Extraction, Article, Physical, chemical, mathematical & earth Sciences :: Chemistry, and Physique, chimie, mathématiques & sciences de la terre :: Chimie

Microcrystalline waxes are mixtures of solid, saturated hydrocarbons mainly branched and characterized by a carbon number over C60. They are used as food additives for the surface treatment of confectionery and some fruit varieties, in chewing gum base, protective coatings, defoaming agents, and surface finishing agents. Commission Regulation No 231/2012 established physical and chemical specifications for microcrystalline waxes to use in food, and posed a limit of 50 μg/kg for benzo(a)pyrene. Due to the low solubility of microcrystalline waxes in organic solvents and matrix interferences, analytical determination of benzo(a)pyrene represents a difficult task. The official method for indirect determination of total polycyclic aromatic hydrocarbons uses unspecific spectrophotometric detection and a quite laborious, time- and solvent-consuming extraction method. A liquid-liquid partition method followed by solid-phase microextraction was developed to isolate benzo(a)pyrene from the bulk of saturated hydrocarbons in microcrystalline waxes, with the aim to have a simple and effective method to verify compliance with the legal limit. The final determination was carried out by gas chromatography coupled to mass spectrometry. Good linearity was obtained, along with a recovery of about 80% from the liquid-liquid partitions. The repeatability of the entire method was <6% and accuracy was <3%. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Concrete, Mechanical interlocking, Repair, Roughness, Microcracking, Pull-off test, Adhesion, Surface treatment, Engineering, computing & technology :: Civil engineering, and Ingénierie, informatique & technologie :: Ingénierie civile

One of the main processes for repairing concrete structures is patch repair. Efficiency and durability of a repaired system depends on the bond between concrete substrate and repair material. By increasing the surface roughness, the surface treatment of concrete substrate can promote mechanical interlocking that is one of the basic mechanisms of adhesion. Nevertheless, some problems may arise from “co-lateral” effects of the treatment, especially due to the development of microcracks inside the substrate. In the presented paper, the effect of concrete substrate surface preparation has been characterized by roughness measurement, description of microcracking in the near-to-surface layer and a pull-off cohesion test. After repair, pull-off bond strength has been evaluated. It is concluded that selection of a suitable surface treatment technique should be preceded by the analysis of its aggressiveness in relation to the concrete substrate strength. A procedure for bond strength estimation using multiple regression approach, based on parameters describing surface quality really generated from various roughening techniques, is then proposed.

Alkanethiol, Copper, Dithiocarboxylic acid, Self-assembled monolayers, Aliphatic thiols, Alkanethiols, Cathodic desorption, Comparative studies, Contact angle goniometry, Copper surface, Dithiocarboxylic acids, Dithiols, Electrochemical studies, Lithographic patterning, Metallic substrate, Molecular organization, Organothiols, Other applications, PM-IRRAS, Polycrystalline copper, Sams, Stable films, XPS, Acids, Contact angle, Corrosion resistance, Desorption, Protective coatings, Rapid solidification, Self assembly, Stripping (removal), Substrates, Surface treatment, Self assembled monolayers, Physical, chemical, mathematical & earth Sciences :: Chemistry, and Physique, chimie, mathématiques & sciences de la terre :: Chimie

The stability of alkanethiol self-assembled monolayers (SAMs) on metallic substrates, in particular copper, is an important aspect for their application. Some technologies, such as lithographic patterning, can potentially benefit from the use of a transient easily removal protective coatings. Other applications like corrosion resistance, and thin-film lubrication request rather robust and stable films. The aim of this work consists in a comparative investigation of three organothiols (n-tetradecanethiol or RSH, 2-dodecylpropane-1,3-dithiol or R(SH)2 and n-tetradecanedithiocarboxylic or RS2H) on their ability to form SAMs on electrochemically reduced polycrystalline copper substrates and their respective stability. Characterizations of the SAMs are carried out using contact angle goniometry, XPS, PM-IRRAS and electrochemical studies (CV, LSV and cathodic desorption). R(SH)2 leads to monolayers with lower molecular organization than in the case of RSH and RS2H molecules. R(SH)2 monolayers are found the more stable when subjected to both anodic and cathodic desorption tests. © 2009 Elsevier B.V. All rights reserved.

concrete structure, repair, surface treatment, surface geometry, bond strength, Engineering, computing & technology :: Materials science & engineering, and Ingénierie, informatique & technologie :: Science des matériaux & ingénierie

The aim of this work to analyse the relationships between parameters of concrete surface geometry determined with various methods as well as their relations to adhesion in repair systems. Several types of concrete preparation techniques were selected to obtain different levels of surface roughness of concrete substrates. Four measurement techniques, corresponding to different levels of observation, have been used to characterize the surface geometry: laser profilometry, mechanical profilometry, a microscopic method and a "sand" (macroscopic) method. The correlations between parameters describing surface geometry are determined. The relationships between bond strength and selected parameters of surface geometry are also discussed. (c) 2005 Elsevier Inc. All rights reserved.