Search results for "silica gel"
showing 10 items of 91 documents
Contributions to the analysis of organic xenobiotics in fish
1995
For the residue-analysis of fish samples, a method has been developed to separate the medium polar triazines and acetamides together with lipophilic xenobiotics (organochlorine pesticides, PCBs and octachlorostyrene) from fish tissue. The detection limits of the analytes are mostly within the ppt-range (ng/kg fillet) and vary between 40 and 1050 ng/kg fillet of fish. Their recoveries range from 75 to 108%, spiked at 1.5 μg/kg. The substances are extracted with a mixture of petroleum ether/ethylacetate (2:1) using a soxhlet apparatus. Subsequently, the lipids in the sample extracts are reduced to 0.4% by gel chromatography. A 5 g silica gel clean-up separates the analytes according to their …
Separation of plasma membrane proteins of cultured human fibroblasts by affinity chromatography on bonded microparticulate silicas.
1984
Abstract Adsorbents for high-performance affinity chromatography were prepared by bonding proteins and reactive Procion triazine dyes to 3-isothiocyanatopropyl- and 3-aminopropylsilicas. The materials prepared were used successfully in the separation of hydrophobic plasma membrane proteins of cultured human fibroblasts. The data obtained show that the reaction of 3-isothiocyanatopropyltriethoxysilane (ITCPS) with the surface hydroxyl groups of silica yields a new and convenient route to preparing an “activated carrier” that is capable of coupling with potential affinity ligands containing amino functional groups. The reaction and bonding procedures of 3-isothiocyanatopropyltriethoxysilane a…
Development and optimization of gas chromatography coupled to high resolution mass spectrometry based method for the sensitive determination of Dechl…
2017
An analytical method has been developed for the trace determination of 10 dechlorane-related compounds (DRCs) in food products by gas chromatography - high resolution mass spectrometry (GC-HRMS). The highest sensitivity of this instrumental analysis method was achieved by selection of the GC column type, optimization of the heated zones within the instrument, and adjusting the electron impact energy. The efficiency of solid phase extraction as clean-up procedure was also optimized. Two different types of cartridges - neutral silica gel and Florisil®, as well as seven organic solvents or their mixtures - n-hexane, cyclohexane, acetone, toluene, n-hexane/ethyl acetate, n-hexane/acetone, and n…
Effect of silica-type sol–gel carrier’s structure and morphology on a supported Ziegler–Natta catalyst for ethylene polymerization
2006
Abstract Silica xerogels with different structures and morphology, synthesized using a sol–gel procedure, were used as a carrier of vanadium catalysts (VOCl 3 /AlEt 2 Cl) for ethylene polymerization. Two techniques of catalyst synthesis were applied: slurry impregnation and gas-phase adsorption and the relevant polymerization methods were then employed. The effect of the carrier structure and morphology on the vanadium loading in the catalysts, the catalyst’s activity and kinetic stability were investigated.
Separation of pesticides, related compounds, polychlorobiphenyls and other pollutants into four groups by silica‐gel microcolumn chromatography (appl…
1991
Multi‐residue analyses of pesticides and related compounds generally require clean‐up procedures for the elimination of interfering substances. An analytical procedure for use in the recovery and determination of pesticides and other pollutants in water samples is described, in which the purification of the extracts is improved by the separation of pesticides into four groups. The separation of pesticides by silica‐gel microcolumn chromatography is explained in detail. Copyright © 1991 John Wiley & Sons, Ltd
Efficient Removal of Methyl Red Dye by Using Bark of Hopbush
2022
Methyl red (MR) dye, one of the azo dyes, is mutagenic and its persistence has negative effects on the environment and people’s health. The current work is the first to demonstrate that methyl red dye can be removed effectively and sustainably, utilizing biomass derived from the bark of the Dodonaea viscosa (Hopbush) plant. The Hopbush bark shows effective adsorption of MR, upto 73%, under optimized conditions in an aqueous medium. The experimental conditions were optimized by examining the effect of time, initial dye concentration, pH and ionic strength on the adsorption process in an aqueous medium. Maximum (i.e., 73%) adsorption of MR removal (500 ppm) was observed in highly acidic…
HPTLC and GC-MS for separation and identification of eugenol in plants
2007
Samples of clove, nutmeg, and cinnamon have been extracted by maceration with ethanol for 24 h and with aqueous ethanol 48 h. Rhizomes of herb bennet ( Geum urbanum ) and calamus ( Aconum calamus ) and roots of valerian ( Valeriana officinalis ) have been subjected to aqueous hydrolysis then extraction with dichloromethane. The active principles from the samples were separated on silica gel HPTLC plates, with pure (standard) and dental (pharmaceutical) eugenol, using n -heptane-ethyl acetate 60+40 ( v / v ) as mobile phase. After development the components were visualized in UV light at λ = 254 nm. The presence of eugenol was confirmed by GC-MS.
Palladium Supported on Cross-Linked Imidazolium Network on Silica as Highly Sustainable Catalysts for the Suzuki Reaction under Flow Conditions
2013
Highly cross-linked imidazolium-based materials, obtained by radical oligomerization of bis-vinylimidazolium salts in the presence of 3-mercaptopropyl-modified silica gel, were used as supports for palladium catalysts. Thanks to the high imidazolium loading these materials were able to support a high amount of the metal (10 wt%). Such materials were characterized by several techniques (13C magic angle spinning nuclear magnetic resonance, the Brunauer-Emmett-Teller technique, X-ray photoelectron spectroscopy, and transmission electron microscopy). The palladium catalysts displayed good activity allowing the synthesis of several biphenyl compounds in high yields working with only 0.1 mol% of …
Cryopreservation of Italian cultivars of hazelnut
2021
The present study was performed to optimise the cryopreservation protocol in Italian cultivars of Corylus avellana L. Lateral buds excised from in vitro grown plantlets of ‘Tonda Gentile Romana’ (TGR) and ‘Montebello’ (MB) were cryopreserved by the encapsulation-dehydration technique. The effect of dehydration of beads with sucrose (0.5, 0.75 or 1 M) for 1 or 3 days, of desiccation with silica gel for 6 or 8 h and of application of two cytokinins (N6-benzyladenine or meta-Topolin) in the regrowth phase was evaluated. The highest regrowth was obtained dehydrating alginate beads with 0.75 M sucrose applied for 1 day and with desiccation for 8 h with silica gel in both cultivars. On the other …
Factors affecting copper(II) binding to multiarmed cyclam-grafted mesoporous silica in aqueous solution
2009
Single- as well as multi-anchored cyclam-functionalized silica samples have been prepared by grafting amorphous silica gel (K60) and mesostructured silica (SBA-15) with silylated cyclam precursors bearing one, two, or four triethoxysilyl groups, respectively ascribed to cyclam-mono, cyclam-di, and cyclam-tetra. Their reactivity toward copper(II) has been thoroughly investigated in aqueous solution and discussed with respect to the number of arms tethering the ligand to the silica surface and the structural ordering of the adsorbent in terms of capacity, long-term stability, and speed of access to the binding sites. Less-than-complete metal ion uptake was always observed, even in excess of c…