Topic
Silica gel
About: Silica gel is a research topic. Over the lifetime, 22313 publications have been published within this topic receiving 325516 citations. The topic is also known as: Amorphous silica & Precipitated amorphous silica.
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TL;DR: All the reactions dealing with air or moisture sensitive compounds were carried out in a dry reaction vessel under a positive pressure of argon or nitrogen.
Abstract: General. All the reactions dealing with air or moisture sensitive compounds were carried out in a dry reaction vessel under a positive pressure of argon or nitrogen. Airand moisture-sensitive liquids and solutions were transferred via syringe or stainless steel cannula. Analytical thin-layer chromatography was performed using glass plates pre-coated with 0.25-mm 230‐400 mesh silica gel impregnated with a fluorescent indicator (254 nm). Thin layer chromatography plates were visualized by exposure to ultraviolet light (UV) and/or by immersion in an acidic staining solution of p-anisaldehyde followed by heating on a hot plate. Organic solutions were concentrated by rotary evaporation at ca. 15 Torr (evacuated with a diaphragm pump). Flash column chromatography was performed as described by Still et al., 1 employing Kanto Silica gel 60 (spherical, neutral, 140‐325 mesh). Materials. Commercial reagents were purchased from Tokyo Kasei Co., Aldrich Inc., and other commercial suppliers and were used either distilled or recrystallized before use. Zinc chloride (anhydrous, beads, -10 mesh, 99.99 %) was purchased from Aldrich and was flame-dried just before use. Anhydrous tetrahydrofuran (THF) and diethylether were purchased from Kanto Chemical Co. and distilled from sodium / benzophenone ketyl at 760 Torr under an argon atmosphere immediately before use. TMEDA and toluene were distilled from calcium hydride at 760 Torr under an argon atmosphere immediately before use. Triethylamine was distilled from calcium hydride at 760 Torr under an argon atmosphere and was subsequently stored over 4-A molecular sieves in a storage flask. The water content of the solvent was confirmed with a Karl-Fischer moisture titrator to be less than 20 ppm. The following starting materials were prepared as described in the literature: 2-phenylethynylphenol, 2 2-(1-hexynyl)phenol, 2
123 citations
TL;DR: A carbon paste electrode modified with aminopropyl-grafted silica gel (APS) was evaluated as an electrochemical sensor for copper species in aqueous medium as discussed by the authors.
Abstract: A carbon paste electrode modified with aminopropyl-grafted silica gel (APS) was evaluated as an electrochemical sensor for copper species in aqueous medium. The overall analysis involved a two-step procedure: an accumulation step at open circuit, followed by medium exchange to a pure electrolyte solution for the voltammetric quantification. During the preconcentration step, copper(II) was accumulated on the APS surface by complexation with the amine groups. In the detection step, copper(II) was desorbed in acidic medium, then cathodically electrolyzed at −0.5 V for 60 s, and detected by anodic stripping square wave voltammetry. The influence of various experimental parameters on the sensor response was investigated (i.e. pH of the detection and accumulation media, electrolysis time, carbon paste composition, silica gel porosity, accumulation time). Reproducible results were obtained, giving after optimization a linear calibration in the 5×10 −8 –2×10 −7 M concentration range, with a detection limit of 3×10 −9 M. This new sensor was applied to copper analysis in laboratory tap water.
123 citations
TL;DR: In this paper, reversed phase adsorption with octadecyl-modified silica gel was found to give quantitative recoveries of di-, tri-, tetra-and pentachlorophenol, tri- and tetrachloroguaiacol and tri-and tetrachelorocatechol from water.
123 citations
TL;DR: In this article, a method for the analysis of fatty esters employing separation by thin-layer chromatography and quantitative determination via their hydroxamic acids has been developed, which is suitable for analysis of mixtures of ordinary, epoxy, monohydroxy, and dihydroxy fatty acids.
Abstract: A method for the analysis of fatty esters employing separation by thin-layer chromatography and quantitative determinationvia their hydroxamic acids has been developed. Esters of different types are separated on silica gel plates, the spots or zones are scraped from the plates, the esters are extracted from the silica gel, and the iron hydroxamic acid complexes are formed. The latter are then measured by colorimetry. The method is suitable for analysis of mixtures of ordinary, epoxy, monohydroxy, and dihydroxy fatty esters as well as for mixtures of mono-, di-, and triglycerides. Used in conjunction with gas chromatography this method permits the fatty acid composition of seed oils containing oxygenated fatty acids to be measured in about 3 hours. The amount required for the total analysis is 1 to 10 mg. per determination, depending upon composition.
122 citations
TL;DR: In this article, a 3-aminopropyltriethoxysilane (3-AMP) modified with 3-AMP was anchored with resacetophenone to prepare a new chelating surface (or matrix).
122 citations