Silica-based Octyl Research Articles

Application of a Macroporous Silica-Based CMPO-Impregnated Polymeric Composite in Group Partitioning of Long-Lived Minor Actinides from Highly Active Liquid by Extraction Chromatography

A macroporous silica-based octyl(phenyl)-N,N-diisobutylcarbamoylmethylphoshine oxide (CMPO) chelating polymeric composite, CMPO/SiO2−P, was synthesized by impregnating and immobilizing CMPO into th...

Resistant behavior of a novel silica-based octyl(phenyl)- N, N-diisobutyl carbamoylmethylphoshine oxide neutral extraction resin against nitric acid, temperature and γ-radiation

The resistant behavior of a novel silica-based octyl(phenyl)- N, N-diisobutylcarbamoyl-methylphoshine oxide (CMPO) extraction resin (CMPO/SiO 2-P) against HNO 3, temperature and γ-radiation had been investigated. The adsorption properties of the treated CMPO/SiO 2-P resin were evaluated by a 3 M HNO 3 solution containing 0.01 M Nd(III). It was found that 3 M or 0.01 M HNO 3 concentration did not decrease the stability of CMPO/SiO 2-P at 25°C. The HNO 3 concentration effect on the leakage of CMPO/SiO 2-P resin at 80°C was obviously higher than that of at 25°C. The adsorbed amount of Nd(III) onto the treated CMPO/SiO 2-P resin was determined in the range of 0.1769–0.1839 mmol/g, which basically approached to 0.1875 mmol/g, the adsorbed quantity of fresh CMPO/SiO 2-P resin for Nd(III). The contents of P and C leaked from CMPO/SiO 2-P resin obviously increased with an increase in the radiation dose ( ID) from 1.0 to 4.1 MGy in terms of the linear equations: [P]=110.05 ID+21.92 and [C]=7683.8 ID−919.8. The adsorbed amount of Nd(III) onto the radiated CMPO/SiO 2-P resin quickly decreased from 0.1499 to 0.0900 mmol/g according to the equation Q Nd(III)=−0.0222 ID+0.1778, showing a large quantity of CMPO leaked from CMPO/SiO 2-P resin.

Antimony speciation by inductively coupled plasma mass spectrometry using solid phase extraction cartridges.

A novel and simple method for inorganic antimony speciation is described based on selective solid phase extraction (SPE) separation of antimony(III) and highly sensitive inductively coupled plasma mass spectrometric (ICP-MS) detection of total antimony and antimony(V) in the aqueous phase of the sample. Non-polar SPE cartridges, such as the Isolute silica-based octyl (C8) sorbent-containing cartridge, selectively retained the Sb(III) complex with ammonium pyrrolidine dithiocarbamate (APDC), while the uncomplexed Sb(V) remained as a free species in the solution and passed through the cartridge. The Sb(III) concentration was calculated as the difference between total antimony and Sb(V) concentrations. The detection limit was 1 ng L(-1) antimony. Factors affecting the separation and detection of antimony species were investigated. Acidification of samples led to partial or complete retention of Sb(V) on C8 cartridge. Foreign ions tending to complex with Sb(III) or APDC did not interfere with the retention behavior of the Sb(III)-APDC complex. This method has been successfully applied to antimony speciation of various types of water samples.

Sulphonated azoligand for metal ion determination in ion interaction chromatography

An azosulphonated ligand, namely cyclo-tris-7-(1-azo-8-hydroxynaphthalene-3,6-disulphonic acid), Calcion, which is generally used as a metallochromic indicator for metal ion titrations, has been studied in order to verify its suitability as a new ligand for metal ion separation in a liquid chromatography technique based on the ion interaction mechanism. Before chromatographic method development, studies on the complexation capabilities of Calcion with Ni 2+, Cu 2+, Fe 3+ and Al 3+ metal ions were performed, determining the stability constants of the complexes between such metal ions and the ligand. The procedure is based on ion-exchange chromatography and involves the retention of the negatively charged complexes on an anion-exchange resin and the determination of free and complexed metal by inductively coupled plasma atomic emission spectrometry. Chromatographic separation of Ni 2+–Cu 2+and Fe 3+–Al 3+ was reached, using a silica-based octyl stationary phase, through pre-complexation with Calcion, and UV–visible detection of the resulting anionic complexes. The effect of the main mobile phase parameters (concentration of the ion interaction reagent tetrabutylammonium chloride, organic modifier methanol and pH) on k′ of analytes was studied and optimization of the metal ion separation was achieved. In order to obtain the simultaneous determination of metal ions, the concentration of CH 3OH and pH gradient elution were also considered. The method developed has been applied to tap water analysis.

Characterization of silica-based octyl phases of different bonding density: Part II. Studies of surface properties and chromatographic selectivity

The goal of the current work was to evaluate changes in the surface composition of the stationary phase as a function of the bonded ligand density. To fulfill this purpose several octyl phases of different surface coverage were synthesized from the same support silica. For each chromatographic system the methylene selectivity measurements were used to estimate the equilibrium sorption constant and surface excess of acetonitrile in the stationary phase. The differences in the stationary phase composition were correlated with the surface properties of the corresponding chromatographic packings, which were characterized by nitrogen adsorption, thermogravimetry and solid-state NMR.

Characterization of silica-based octyl phases of different bonding density: Part I. Thermal stability studies

Chemically bonded phases for reversed-phase chromatography are often produced via reaction of silica gel with appropriate organosilane. Although this reaction is commonly used and well-documented in literature, little attention has been paid so far to study the postreaction curing process. In the current paper the effect of the curing process on the thermal stability of the synthesized octyl phases has been investigated by means of thermogravimetry and solid-state NMR techniques. The study shows that the postreaction isothermal equilibration of the samples dramatically improves their thermal stability without a substantial mass loss due to thermodesorption of silane. Curing process promotes condensation reaction of surface hydroxyls with hydrolyzed silane molecules increasing surface coverage of the synthesized chemically bonded phases.

Adsorption, Thermogravimetric, and Chromatographic Studies of Bare Silicas and Silica-Based Octyl Bonded Phases

Structural and surface properties of seven chromatographic silica gels were characterized by means of nitrogen adsorption and high-resolution thermogravimetry. The retention of alkyl benzenes was measured using the corresponding commercial octyl-bonded phases. The partition-displacement model was used to evaluate the equilibrium sorption constant and the surface excess of acetonitrile for each octyl phase. Most of the stationary phases studied showed similar sorption properties and, consequently, comparable values of the acetonitrile surface excess. Only for one of the phases studied the surface excess was much higher, and that was attributed to the difference in the silanol coverage of the stationary phase.

Comparative Characterization of Octyl Bonded Phases using Methylene Selectivity Data

Retention measurements of alkyl benzenes were carried out on the synthesized silica-based octyl bonded phases. The partition-displacement model was employed to analyze chromatographic properties of these phases. Namely, the methylene selectivity data were used to calculate the equilibrium sorption constant, the surface phase composition, and the sorption excess of water for each octyl phase. The differences in the surface phase composition of the phases studied were correlated with the structural and surface properties of the modified silica gels.