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: In this paper, a red-shifted structureless absorption band characteristic of a ground-state charge transfer (CT) complex formed between polycyclic aromatic hydrocarbons (PAH) and methyl viologen dication (MV ++ ) is observed.
Abstract: Porous silica surfaces are shown to slowly catalyze the oxidation of adsorbed polycyclic aromatic hydrocarbons (PAH) to the corresponding radical cation via Lewis acid sites present on the surface. When a good electron acceptor such as methyl viologen dication (MV ++ ) is co-adsorbed on silica surface, a red-shifted structureless absorption band characteristic of a ground-state charge transfer (CT) complex formed between the PAH and MV ++ is observed. Oxygen efficiently competes with MV ++ for the trapped electrons on the active sites of silica surface causing a significant decrease in the concentration of ground-state CT complex. The rate of this electron transfer process is enhanced dramatically at the solid/liquid interface when solution of PAH in a non-polar solvent is added to dry silica containing adsorbed MV ++ . Room temperature electron paramagnetic resonance (EPR) spectra of PAHs adsorbed on silica show a broad unresolved signal ( g =2.0031–2.0045) due to PAH ⋅+ radical cation which disappears in the presence of air but can be restored upon evacuation of the sample. The EPR measurements of mixed samples containing PAH and MV ++ co-adsorbed on silica show a composite signal with hyperfine structure that may be due to presence of two paramagnetic species corresponding to MV ⋅+ and possibly PAH radical cation.
109 citations
TL;DR: The BPA-imprinted polymers were used as the sorbent in solid-phase extraction to determine BPA in water samples with satisfactory recovery higher than 99% and the MIP-SPE-HPLC method showed higher selectivity to BPA than the traditional SPE- HPLC method.
109 citations
TL;DR: In this article, a Horseradish peroxidase (HRP) was immobilised on silica gel modified with titanium oxide, which was employed to prepare modified carbon paste electrode.
109 citations
TL;DR: Sulforaphane, a cancer chemopreventive agent identified from broccoli, was degraded in an aqueous solution at 50 and 100 degrees C and the major thermal degradation compound was determined as N, N'-di(4-methylsulfinyl)butyl thiourea.
Abstract: Sulforaphane, a cancer chemopreventive agent identified from broccoli, was degraded in an aqueous solution at 50 and 100 °C. The reaction mixtures were extracted with methylene chloride and analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). Dimethyl disulfide, S-methyl methylthiosulfinate, S-methyl methylthiosulfonate, methyl (methylthio)methyl disulfide, 1,2,4-trithiolane, 4-isothiocyanato-1-(methylthio)-1-butene, and 3-butenyl isothiocyanate were identified as volatile decomposition products. After methylene chloride extraction, the aqueous layer was dried and silica gel column chromatography was used to separate and purify the nonvolatile decomposition products. The major thermal degradation compound was determined by 1H NMR, 13C NMR, and FAB-MS as N,N‘-di(4-methylsulfinyl)butyl thiourea. A possible mechanism for the formation of these products is proposed.‘ ‘‘ Keywords: Sulforaphane; isothiocyante; thermal decomposition; N,N‘-di(methylsulfinyl)butyl thiourea
109 citations
TL;DR: Scale-up production of ethyl butyrate was examined in a packed column with recycling of n-hexane containing substrates and increased substrate concentrations were stimulatory up to a point after which inhibition and enzyme destabilization in repeated runs occurred.
Abstract: Candidacylindracea lipase adsorbed to silica gel produced a variety of flavor esters when hydrated and shaken in n-heptane containing substrates. Scale-up production of ethyl butyrate was examined in a packed column with recycling of n-hexane containing substrates. Increased substrate concentrations were stimulatory up to a point after which inhibition and enzyme destabilization in repeated runs occurred.
109 citations