Low-Temperature Sorption–Luminescence Determination of Copper in Natural Water Using Silica Gel Chemically Modified with Mercapto Groups

Silica gel with mercaptopropyl groups chemically bonded to its surface extracts copper from solutions with pH 2–9 with a recovery of 99.9%; the sorption equilibration time is no longer than 5 min. Ultraviolet irradiation of wet sorbates cooled to the liquid nitrogen temperature (77 K) generates yellow–orange luminescence (_max = 585 nm), which was used as the analytical signal for the development of a procedure for the low-temperature sorption–luminescence determination of copper. The detection limit is 0.08 g per 0.1 g of the sorbent. The determination of copper is unaffected by the interference from 10⁴-fold amounts of Zn(II), Cd(II), Mn(II), Ni(II), Co(II), Ca(II), Mg(II), and Al(III); 10³-fold amounts of Fe(III); 30-fold amounts of Bi(III); tenfold amounts of Ag(I); and fivefold amounts of Cr(VI). The procedure was used for the determination of copper in natural water.     

Sorption–Photometric Determination of Osmium after Its Extraction from the Gas Phase with Silica Gel Chemically Modified with Mercapto Groups

The sorption of osmium(VIII) from H₂SO₄ solutions and from the gas phase with silica gels chemically modified with mercapto or disulfide groups was studied. A procedure is proposed for the sorption–photometric determination of osmium including the oxidation of osmium, the sorption of OsO₄ from the gas phase with silica gel chemically modified with mercapto groups, and the determination of osmium in the sorbent phase by diffuse reflectance spectrometry. The detection limit is 0.5 g of Os per 0.2 g of the sorbent. The calibration plot is linear up to 700 g Os/0.2 g. The relative standard deviation in the determination of more than 15 g is no larger than 6%. The procedure was used for the determination of osmium in standard reference samples of platinum concentrates.     

Low-Temperature Sorption–Luminescence Determination of Platinum Using Silica Chemically Modified with N-Allyl-N"-Propylthiourea and N-Phenyl-N"-Propylthiourea

Silicas chemically modified with N-allyl-N"-propylthiourea and N-phenyl-N"-propylthiourea were proposed for the low-temperature sorption–luminescence determination of platinum. The sorption of platinum(II) and platinum(IV) at the surface of sorbents yields coordination compounds luminescing at 77 K under UV irradiation. Luminescence spectra of platinum(II) complexes of thiourea derivatives covalently bonded to the silica surface exhibit a broad structureless band with a maximum at 585 nm. For the sorbent with N-allyl-N"-propylthiourea groups, the detection limit of platinum is 0.1 g per 0.1 g of the sorbent. The calibration plot is linear up to 50 g/0.1 g. The detection limit and the linearity range of calibration plots depend on the mass of the sorbent. The proposed procedure was used for the analysis of aluminoplatinum catalysts.     

Study of the Nano-Size Silica Sol–Gel Film as the Matrix of Chemically Modified Electrode

This paper reports a new method to make the sol–gel film from silicate. It provided more profitable conditions than hydrolysis of alkoxyl silane to prepare the high-quality nanometers thin film. The thin film could be applied as the matrix to directly modify the molecules of methylene blue on electrode surface and kept their electrochemical activity excellently. It exhibited the remarkable catalytic activity for the oxidation of NADH or reduction of hemoglobin while severally embedding them in the sol–gel film together with methylene blue.     

Effect of Synthesis Parameters on Sol–Gel Silica Modified by Zirconia

An experimental strategy was developed to obtain mesoporous SiO₂-ZrO₂ mixed oxides via a sol–gel process, which involved the use of tetraethylorthosilicate (TEOS) and an inorganic Zr-containing salt. The effects of key process parameters on the properties of the materials were investigated, including the choice of Zr(IV) source (zirconium oxychloride or nitrate), the ZrO₂ content and the synthesis pressure (i.e. ambient pressure or hydrothermal conditions). The resulting solids were dried, calcined at 500 °C, and characterized by nitrogen physisorption, pyridine chemisorption, ²⁹Si Nuclear Magnetic Resonance and X-ray diffraction. The data revealed that mesoporous materials with very narrow pore diameter distribution were obtained when using the autoclave procedure from both zirconium nitrate and oxychloride salts. The surface areas and pore size distributions were a function of ZrO₂ content. Differences in acidity, as determined by pyridine adsorption, were observed depending on the synthesis parameters.     

Separation of β-Blocker Enantiomers on Silica Modified with Gold Nanoparticles with Immobilized Macrocyclic Antibiotic Vancomicin

A new chiral sorbent based on mercaptosilica modified by gold nanoparticles, then treated by 3-mercaptopropionic acid and macrocyclic antibiotic vancomycin, was obtained. The enantioseparation of isomeric β-blockers (nadolol, atenolol, metoprolol, alprenolol, oxprenolol, and pindolol) by HPLC was studied on the synthesized sorbent. The effect of the composition of the mobile phase (nature and concentration of the organic solvent, concentration and pH of the buffer solution) on retention times of β-blocker enantiomers, selectivity of separation, and resolution of chromatographic peaks were studied. The best separation was achieved for pindolol and metoprolol. The procedure was used to determine the pindolol enantiomers in the preparation “Visken,” and metoprolol in the “Vazocardin” preparation.     

A Gas Chromatographic Analysis of Light Hydrocarbons on a Column Packed with Modified Silica Gel

IntroductionAnalysis of light hydrocarbons achieved by gas-solid chromatography is important in petrochemical industry, environmental protection and some other areas. A variety of columns have been used, including conventional packed column1, Al2O3 and graphitized carbon black PLOT column2, 3 and silica gel SCOT column4. Al2O3 PLOT column is excellent for the analysis of light hydrocarbons. Conventional packed column also has its own advantages, such as easy column preparation, resistanc…     

Adsorption Properties of Mesoporous Silica Gel with β-Cyclodextrin as a Pore-Forming Agent Relative to Moxifloxacin

A method for the synthesis of mesoporous silica gel using β-cyclodextrin as a pore-forming agent is developed. The physical properties and structure of the obtained adsorbent are studied by Fourier-transform IR spectroscopy and the low-temperature adsorption–desorption of nitrogen (BET) method. The material has an average specific surface area of 435 ± 5 m²/g and an average pore size of 5 ± 0.5 nm. This value of the pore size indicates the formation of complex structures from columnar associates of β-cyclodextrin in the synthesis of the material. The adsorption capacity of the obtained material is 0.2 ± 0.05 mg of 2-hydroxypropyl-β-cyclodextrin per milligram of the adsorbent. The dissociation constant of the complexes of moxifloxacin with β-cyclodextrin inside the pores of silica gel is of the order of 5 × 10^–3 M. The resulting system of SiO₂-β-CD is promising for application in the biomedical chemistry as a carrier of biologically active molecules, particularly as an antibacterial preparation of moxifloxacin.     

Conversion of Oxiranes to Thiiranes Catalyzed with Silica Gel–Supported Aluminium Chloride

Silica gel–supported aluminium chloride, SiO₂‐AlCl₃, catalysizes the efficient conversion of different oxiranes to their corresponding thiiranes in the presence of thiourea under nonaqueous conditions.     

Sol–Gel Synthesis of Methyl Modified Optical Silica Coatings and Gels from DDS and TEOS

Methyl modified silica coatings and gels were prepared from dimethyldiethoxysilane and tetraethylorthosilicate via sol–gel processing and spin-coating. The as-synthesized coatings showed not only anti-reflectivity but also hydrophobicity and high laser damage thresholds compared to pure silica coatings without methyl modification. The existence of methyl groups in the framework was demonstrated by IR and NMR spectroscopy. The microstructure of the xerogels obtained were also characterized and will be discussed.     

Adsorption of n-Butanol on Polycrystalline Silver–Gold Alloys

The adsorption kinetics for n-butanol (c _L = 0.033–1.2 M) on polycrystalline electrodes of silver, gold, and their homogeneous alloys (X _Au = 0.15–0.80) formally obeys the Roginskii–Zel'dovich equation. The steady-state coverage of their surface by the alcohol, _L ^st, is described by the Temkin isotherm. The ratio between the slopes of the _L vs. logt and _L ^st, vs. logc _L dependences perceptibly alters with X _Au. The experimental data are discussed in terms of a quasi-equilibrium competing co-adsorption of water and alcohol at an energetically-nonuniform surface accompanied by a relatively slow redistribution of adsorbate molecules between adsorption centers of different nature. It is shown that quantitative characteristics of the n-butanol adsorption on Ag–Au alloys cannot be calculated in the approximation of additivity of properties on the basis of relevant parameters of adsorption on Ag and Au.     

Fibrous Silica Composites Fabricated Via Sol–Gel Processing Using Amino Acid Surfactant Templating

Fibrils covered by a silica shell have been fabricated by using fibrous aggregates of amino acid surfactant, N-dodecanoyl--alanine, as a template for silicate generated in situ by sol–gel processing in an aqueous solution at pH around 6 and ambient temperature. It was shown that these conditions were inappropriate for tetraethoxysilane to generate silica. The synthesis was performed only when a new water-soluble precursor, tetrakis (2-hydroxy ethyl) orthosilicate, was applied. It is suggested that silica nucleation on the surfactant fibrils takes place via the formation of hydrogen bonds with corresponding functional groups of the amino acid residues.     

Sorption Properties of α-Aluminum Oxide Modified with Decationized Silica Sol

The method of sorption of tetrachloromethane vapor at the solid/gas interface was applied to study the sorption and structural properties of a mesoporous aluminum oxide material obtained by deposition of amorphous hydrated silicon(IV) oxide onto -aluminum oxide particles submerged in decationized silica sol.     

Determination of Nicotine in Dried Mushrooms by Using a Modified QuEChERS Approach and GC–MS–MS

Levels of nicotine higher than the maximum residue level were detected in edible mushrooms. Analyses of self-collected and purchased dried mushrooms were performed with a QuEChERS approach. A small amount (2.5 g) of dried sample matrix was mixed with 5 mL sodium hydroxide solution, 2.5 g of sodium sulfate/sodium chloride mixture (4:1) and 5 mL ethyl acetate. The organic phase was cleaned by using dispersive solid-phase extraction and analysed by GC–MS–MS. The linear range of the method was 0.01–10.00 mg kg^?1 and the limit of detection 0.006 mg kg^?1 on dry weight basis by using EURACHEM method.     

Polyaphrons as Templates for the Sol–Gel Synthesis of Macroporous Silica

Macroporous silica was synthesized using polyaphrons as shape-directing templates in a sol–gel hydrolysis scheme using tetraethyl orthosilicate (TEOS). Polyaphrons are a special class of high internal phase ratio emulsions (HIPRE) that can potentially be used in the continuous processing of long range ordered macroporous solids. The structures so formed were examined using a scanning electron microscope after thermal curing to 400C. The majority of the pores in the silica structures were in the range between 0.1 and 10 m. Key parameters affecting the polyaphrons template characteristics were varied and their effects on the final silica structure were studied.     

Microbe Modified Carbon Paste Electrode for Determination of Trance Amount of Gold (Ⅲ)

Electrochemical analysis of trace amount of metal ions can be improved by the stripping analysis using chemically modified electrodes. Here we introduce a novel method for preparation of microbe-modified carbon paste electrode for determination of gold(Ⅲ). The preparation method is simple and the electrode obtained is both stable and sensitive in determination of trace amount of gold(Ⅲ).     

Determination of Some Heavy-metal-ions Using a Sulfur Ion Modified BZ Oscillating System

The oscillating reaction as one important phenomenon of nonlinear chemistry has been a focus in recent years. Among all oscillating systems, Belousov-Zhabotinskii (BZ) oscillating system was first found and studied extensively. The mechanism of BZ oscilla…     

Oxidation of Sulfides with N‐Bromosuccinimide in the Presence of Hydrated Silica Gel

An efficient and highly selective procedure for oxidation of sulfides to sulfoxides with N‐bromosuccinimide (NBS) in the presence of hydrated silica gel has been developed. Hydrated silica gel supplies the water necessary for decomposition of the intermediate bromosulfonium salt to the product, allowing the reaction to employ a nonaqueous media. Also, this procedure has increased the scope of the reaction by oxidizing a wider variety of sulfides, which was not possible until now.