S.M. Staroverov

Apparent simplicity of reversed stationary phases for high-performance liquid chromatography

Abstract The effect of pretreatment and the pore structure of the support, the type of silicon—carbon anchor group and the chain length of the alkyl modifier, the chemical modification procedures and the operating conditions on the characteristics and the structure of the bonded layer of reversed stationary phases for high-performance liquid chromatography have been studied.

Geometric structural properties of bonded layers of chemically modified silicas

Abstract The effects of the support structure and the modifier structure on the characteristics of chemically modified stationary phases (bonding density, thickness of the bonded layer) were studied and the principle of geometric structural conformity was formulated. It has been demonstrated that reversed phases can be divided into “rigid”, “flexible” and intermediate structures of a bonded layer. Only structurally uniform stationary phases have been found to possess similar properties.

Enantiorecognition of profens by capillary electrophoresis using a novel chiral selector eremomycin

The evaluation of a macrocyclic glycopeptide antibiotic, eremomycin, as a chiral selector in capillary electrophoresis (CE) has been performed. The stability of eremomycin in solution and capillary electrolyte, as well as its optical and electrophoretic properties have been discussed. The effect of experimental parameters influencing the enantioseparation of several profens has been studied. Excellent enantioseparation of profens has been achieved and migration order has been validated. Comparison of enantioseparations of profens in CE by using eremomycin-mediated electrolytes and in HPLC with eremomycin immobilized on silica has revealed similar trends for both methods.

STRUCTURE OF THE BONDED LAYER AND SELECTIVITY OF CHEMICALLY MODIFIED STATIONARY PHASES FOR CHROMATOGRAPHY

Abstract Studies of the effects of the chemical nature and geometrical parameters of the support, the type of organosilicon anchor grouping, the length of the hydrocarbon chain, the nature of the modifier functional group and silanization of the support on stationary phase selectivity are reported.

Diffusion of sorbed pyrene in the bonded layer of reversed phase silicas: Effect of alkyl chain length and pore diameter

Abstract The processes of lateral diffusion of solutes in the bonded layer of n-alkylchlorosilane-modified silicas were studied using pyrene as a luminescence probe. It was shown that all bonded-chain carbon atoms interact with the solute for supports of pore diameter 40–50 nm. The reduction of the average pore diameter results in partial permeation of the solute into the bonded layer, which in turn leads to a decrease in apparent viscosity of the bonded layer. The presence of accessible silanol groups causes a strong decrease in pyrene mobility in the bonded layer.

Nitroxide radicals in studies of the fine bonded layer structure of modified silicas

Abstract Spin probe and spin label methods were applied in studies of the fine structure of both reversed-phase and functionalized modified silicas. The concept of a “rigid” structure for narrow-pore alkyl-modified silicas was experimentally supported. “Two-level” sorption of the solute in the bonded layer of end-capped alkyl-modified silicas was discovered. The stability of arch structures arising in the bonded layer of functionalized modified silicas was studied. It was shown that arch structures could be effectively destroyed in solvents with high basicity.

Silica sorbents with one- and two-site attached bacitracin in affinity chromatography

Abstract It was found that the bifunctional oligopeptide bacitracin A can be attached to a silica surface by either one or two amino groups. The latter, in contrast to the former, is active in specific binding of proteinases.

Enantioseparation of organic acids of pharmaceutical interest using eremomycin as a chiral selector.

Strong adsorption of eremomycin on the fused‐silica capillary wall was used for separation of enantiomers by CE. The capillary with adsorbed chiral selector was shown to be easily prepared and has reproducible properties. The effect of the chiral selector concentration, pH and composition of the BGE, and applied voltage on enantioseparation of acidic compounds, such as profens and aromatic carboxylic acids, was investigated. Two native α‐amino acids, aspartic acid and glutamic acid, were enantioseparated. Fourteen tested compounds (including amino acids) were baseline resolved. Good selectivity of separation (α>1.09) was achieved. The migration order of ibuprofen and ketoprofen enantiomers was determined. The procedures were proposed for the analysis of flurbiprofen and warfarin in pharmaceuticals. Linearity was achieved in the concentration range of 4.0×10−5–2.0×10−3 M for flurbiprofen and 3.2×10−6–4.9×10−6 M for warfarin. The detection limits were found to be about 1×10−5 M for flurbiprofen and 1×10−6 M for warfarin.

Calculation of the characteristics of the bonded layers of reversed stationary phases

A new stationary phase parameter, R, the percentage of rigid structure, was introduced. It will be determined by the structural characteristics of

Separation of enantiomers of N -derivatives of amino acids by capillary electrophoresis using macrocyclic antibiotics

The potential for the application of macrocyclic antibiotic eremomycin as a chiral selector for the separation of enantiomers of N-derivatives of amino acids in capillary electrophoresis was estimated. The influence of several factors (the composition and pH of the running electrolyte, the concentration of the chiral selector, capillary geometry, the value of the applied voltage) on the migration of the derivatives of amino acids and enantioselectivity in the presence of eremomycin was studied in order to choose the separation conditions. Using the example of the dansyl derivatives of amino acids the enantioselectivities of vancomycin and eremomycin in capillary electrophoresis were compared.