Yu. G. Slizhov

Complexation with Metal Chelates at the Phase Interface in Gas Chromatography

A review of studies on the use of the chelate complexes as adsorbents and stationary liquid phases in gas chromatography is made. Data on the processes of complex formation at the phase interface and on the target production of the chelate-containing sorbents with preset properties are generalized. Practical application of the chelate-containing chromatographic packings for analytical separation and sorption concentration of organic substances is considered.

Synthesis and study of structural and chromatographic characteristics of chelate-containing sorbents based on silica gels

New chelate-containing sorbents with grafted layers of nickel acetylacetonate of nickel-malonic and acetoacetic esters were obtained by successive molecular assembly on the surface of silica gel. Their structural and chromatographic characteristics were examined by physical and chemical methods. It was shown that the adsorbents may be used in gas chromatography for separation of light olefins, aromatics and saturate hydrocarbons, and also alcohols, aldehydes, ketones.

Chromatographic properties of mesoporous silica gel modified with acetylacetonates of europium and copper

New mesoporous materials prepared from tetraethoxysilane, i.e., sorbents obtained with the use of surfactants, are synthesized. Their chromatographic polarity is assessed quantitatively. Their Kovats retention indices and Rohrschneider polarity coefficients are calculated. Based on physicohemical data, it is demonstrated that modifying supports with metal chelates changes the structure and properties of the initial sorbents: the differential molar Gibbs free energies rise considerably for sorbent modified with copper acetylacetonate with respect to ethanol (−ΔG′i = 7.09 kJ/mol) and nitromethane (−ΔG′i = 6.75 kJ/mol), relative to the initial silica gel (5.43 and 4.15 kJ/mol, respectively).

Gas-Chromatographic Properties of Silochrom with a Surface Layer of Nickel Dimethylglyoximate and Acetylacetonate Complexes

The separation ability of surface layers of nickel dimethylglyoximate and acetylacetonate bonded to Silochrom S-80 silica gel was studied. The selectivity of separation was estimated for different classes of organic compounds. It was demonstrated that the studied sorbents are promising for the separation of complex mixtures of high-boiling aromatic compounds and oxygen-containing compounds.

Acidic and basic properties of the surface of gas-chromatographic sorbents with grafted metal chelate layers

The acidic and basic properties of the surface of gas-chromatographic sorbents based on silica gels with grafted layers of nickel acetylacetonate and nickel-malonic and acetoacetic esters were studied by pH measurements and the Hammett indicators adsorption method. The acidic and basic state of the surface was shown to depend on the ligand of the modifying addition, the structure of the complex, and the structural and sorption properties of the silica gels used.

Effect of citric acid and ethylene glycol on the formation of calcium aluminate via the sol-gel method

The processes of formation of calcium aluminate via the sol-gel method has been studied by IR spectroscopy, thermal analysis, X-ray powder diffraction, and scanning electron microscopy. The key stages of synthesis to obtain orthorhombic calcium aluminate (solvent removal, stepwise decomposition of the organic polymeric framework, and formation of crystalline aluminate) have been determined. The effect of the composition of the starting mixture on the formation process and the surface morphology of the final product has been demonstrated.

Acid-base properties of the surface of chromatographic sorbents modified by metal acetylacetonates

The acid-base properties of metal acetylacetonates and chromatographic sorbents on the basis of Chromaton N with deposited combined stationary phases from polyethylene glycol (PEG 20M) and nickel(II) and iron(III) acetylacetonates have been investigated by means of pH measurement and Hammett indicator adsorption. The change of the acid-base state of the surface of Chromaton N depending on the nature of a metal of the modifying additive, the complex structure, and the deposition method has been demonstrated.

Sol-gel synthesis and sorption properties of calcium monoaluminate

Method for synthesis of calcium aluminate and sorbents based on this compound was developed on its basis of the sol-gel technology. The method makes it possible to obtain the target product with specific surface areas in the range from 7 to 120 m2 g–1. The compounds obtained were characterized by scanning electron microscopy, X-ray phase analysis, and X-ray fluorescence microanalysis. It was found that the main phase of the sorbents is rhombohedral calcium monoaluminate CaAl2O4. The method of Hammett indicator adsorption was used to determine the content of active centers on the surface of the sorbents and the distribution of these centers over ionization constants. It was shown that the surface characteristics of the sorbents depend on their synthesis method. The retention parameters, polarities, and thermodynamic characteristics were determined for organic compounds of various classes. The possibility of using calcium aluminate modified with sodium chloride for gas-chromatographic separation of aliphatic and aromatic hydrocarbons and carbonyl compounds was demonstrated.

Synthesis of Silokhrom S-120 grafted with transition-metal acetylacetonate layers and its acid-base and chromatographic properties

We have synthesized sorbents based on Silokhrom S-120 silica gel grafted with Ni2+, Co2+, and Cu2+ acetylacetonate layers. Using pH measurements and a Hammett indicator method, we have studied the acid-base properties and composition of donor-acceptor centers on silica gel surfaces before and after modification. We have determined chromatographic retention parameters for test compounds and evaluated the polarity and selectivity of the sorbents. Modification with acetylacetone chelates has been shown to increase the surface acidity of Silokhrom S-120, leading to changes in various types of intermolecular interaction.

Synthesis and study of the composition and properties of chelate complexes of benzoyl acetonates of rare-earth elements and use of these in gas chromatography

Chelate complex cerium [Ce(BA)3)] and europium [Eu(BA)3] benzoyl acetonates were synthesized. According to IR spectroscopic data and elemental analyses, the composition of the complexes is described by the empirical formulas M(BA)3·2H2O. Sorbents based on a mesoporous silica gel modified with cerium and europium benzoyl acetonates were obtained. The nitrogen porosimetry demonstrated that, as the complexes are deposited onto the surface of the starting support, the specific surface area and the pore volume become smaller. The polarity of the sorbents Chromaton N-AW + SiO2 + M(BA)3 with respect to all classes of test compounds decreases in the order CeIII > EuIII. According to the data obtained for the capacity factors, the sorbent modified with cerium benzoyl acetonate selectively separates alcohols, and Chromaton N-AW + SiO2 with deposited chelates Eu(BA)3 shows the best separating capacity for alkanes and alcohols. It was shown that the sorbents can be used in practice for separating gaseous mixtures of light hydrocarbons.