Mikhail M. Ilyin

Investigation of the properties of hypercrosslinked polystyrene as a stationary phase for high-performance liquid chromatography

SummaryThe mechanical rigidity, swelling properties, adsorption selectivity, and chromatographic performance of hypercrosslinked polystyrene (mainly MN-200 or Purosep-200; Purolite, UK) have been studied to evaluate the use of the material as a stationary phase for reversed-phase high-performance liquid chromatography (RPHPLC). By use of inverse size-exclusion chromatography (SEC) this adsorbent, with a high specific surface area of 1500 m2 g−1 was found to have a biporous structure with micropores of ca 1–2 nm and macropores ca 100 nm in diameter. The polymer does not change its volume significantly on changing water for organic solvents. The retention increments for methylene and phenyl groups were calculated and indicated that the mechanism of retention on the hypercrosslinked polystyrene involves π-π interactions and strong hydrophobic interactions. The column performance of the hypercrosslinked polystyrene was found to be acceptable, with reduced plate height increasing very slowly as the linear velocity of the mobile phase increased to high values (up to 20–45 cm min−1). Columns containing hypercrosslinked polystyrene were evaluated for the separation of phenols, dialkyl phthalates, and polyaromatic compounds. On-column preconcentration of trace organic compounds from aqueous media is possible. With smaller particles of hypercrosslinked polystyrene becoming available, this material can be regarded as an alternative to alkylsilica as a hydrolytically stable column-packing material for RPHPLC.

Hypercross-linked polystyrene and its potentials for liquid chromatography: a mini-review

Hypercross-linked polymeric adsorbing materials are obtained under conditions that (i) their polymeric network is formed in the presence of large amounts of a thermodynamically good solvent (porogen) and (ii) the network is rigid. Hypercross-linked polystyrene is a transparent microporous low-density material with an apparent inner surface area of over 1,000 m2/g and an unprecedented adsorption capacity. To enhance the mass transfer, the adsorbent beads may be provided with large transport pores, in addition to the inherent micropores; these beads are opaque. Hypercross-linked polystyrene sorbents are widely used for large scale adsorption of organic compounds from aqueous and gaseous media and for solid-phase extraction of trace components. Novel perspective application areas of the materials are high-performance liquid chromatography column packings and blood purification. Present mini-review summarises basic principles of obtaining hypercross-linked materials, their structural peculiarities and distinguishing properties, as well as major application areas. Important new unpublished data are also included.

Use of the hyper-crosslinked polystyrene sorbents “Styrosorb” for solid phase extraction of phenols from water

The analytical HPLC procedure for the quantitation of trace amounts of phenol and chlorophenols in aqueous media has been supplemented with the on-line preconcentration of phenols in a sorption cartridge packed with microporous hyper-crosslinked polystyrene. The cartridge is coupled in succession with a reversed-phase analytical column, which is operated isocratically in an aqueous acetonitrile eluent (1:1, v/v). Phenol concentrations down to 0.5 μg/l can be detected using a simple 254 nm UV detector.Biporous hyper-crosslinked polystyrene-type sorbents were shown to effectively purify about 100 bed volumes of water from phenol under neutral or acidic conditions and linear flow rates up to 4 cm/min, which could be of great practical importance. Rapid and quantitative elution of sorbates from the hyper-crosslinked polystyrene materials is facilitated by the unique ability of the latter to additionally swell with organic or aqueous-organic eluents applied.

Highly enantioselective hydrogenation of α,β-unsaturated phosphonates with iridium-phosphinooxazoline complex: Synthesis of a phosphorus analogue of naproxen

Abstract A number of pharmaceutically interesting optically active 1-arylethylphosphonates, including a phosphorus analogue of naproxen, has been synthesized with ee 92–95% via asymmetric hydrogenation under mild conditions using [Ir(cod)(phosphine oxazoline)] + [BAr F ] − catalysts.

Synthesis and structure of biologically active ferrocenylalkyl polyfluoro benzimidazoles

Abstract The title compounds were synthesized in quantitative yields by interacting α-hydroxyalkyl ferrocenes with polyfluoroalkyl benzimidazoles in an aqueous-organic medium in the presence of HBF4. The resulting diastereomers and enantiomers were resolved using HPLC on silica bonded chiral stationary phases based on chiral cyclodextrins and cyclic antibiotics. The X-ray determination of molecular and crystal structure of 1-ferrocenylmethyl-2-(trifluoromethoxyfluoromethyl)benzimidazole (1) was carried out.

Formation of regular clusters through self-association of intramolecularly hypercrosslinked polystyrene-type nanosponges

Atactic polystyrene of M = 330,000 Da and Mw/Mn = 1.04 was subjected to chloromethylation. By the heating of chloromethylpolystyrene with SnCl4 in a very dilute solution in ethylene dichloride, the polymeric coils were converted into intramolecularly hypercrosslinked macromolecules, nanosponges, of molecular weight of about 370,000 Da and a diameter of about 17 nm. When in solution, the nanosponges tend to reversibly self-assemble into regular clusters. Size exclusion chromatography and sedimentation analysis corroborate the suggestion that the clusters consist of 13 spherical subunits and thus acquire a molecular weight of about 5.0 × 106 Da and a diameter of about 45 nm.

Atomic force microscopy imaging of novel macromolecular species, nanosponges, and their clusters

Atactic polystyrene of M = 330,000 Da and M w /M n = 1.04 was subjected to a complete chloromethylation. By heating the chloromethyl polystyrene with SnCl 4 in a very dilute solution in ethylene dichloride, the polymeric coils were converted into intramolecularly hypercrosslinked macromolecules, called nanosponges. These species have a molecular weight of about 370,000 Da and a diameter of about 17 nm. When in solution, the nanosponges display a tendency to reversibly self-assemble into regular clusters. Preparative size-exclusion chromatography isolates a fraction consisting predominantly of spherical clusters that are composed of 13 subunits and acquire a molecular weight of approximately 5.0 x 10 6 Da and a diameter of 45 nm. Scanning atomic force microscopy (AFM) provides images of individual nanosponges, N = 13 clusters, as well as higher spherical clusters. The regular spherical species most probably belong to the cluster series N = 1 + Σ(10n 2 + 2), where n is the number of shells around the central nanosponge.

Physicochemical and adsorption properties of hypercross-linked polystyrene with ultimate cross-linking density

The paper describes unexpected properties of hypercross-linked polystyrenes with ultimate cross-linking degrees of 300, 400, and 500%, where three, four, or five methylene links, respectively, could bind each polystyrene phenyl ring to its spacious neighbors. The polymers exhibit a strong electron spin resonance signal, unusual spectra in IR, UV, and visible ranges, and they are not typical dielectrics. The nonfunctionalized hypercross-linked polymers absorb significant amounts of inorganic acids, salts, and bases due to interactions of protons or other cations with electron-donating fragments of the aromatic network with the high extent of mutual connectivity and also due to dispersion interactions of anions with the polymer matrix.

Enantiomeric-Enriched Ferrocenes: Synthesis, Chiral Resolution, and Mathematic Evaluation of CD-chiral Selector Energies with Ferrocene-Conjugates

Enantiomeric-enriched ferrocene-modified pyrazoles were synthesized via the reaction of the ferrocene alcohol, (S)-FcCH(OH)CH3 (Fc = ferrocenyl), with various pyrazoles in acidic conditions at room temperature within several minutes. X-ray structural data for racemic (R,S)-1N-(3,5-dimethyl pyrazolyl)ethyl ferrocene (1) and its (S)-enantiomer (S)-1 were determined. A series of racemic pyrazolylalkyl ferrocenes was separated into enantiomers by analytical HPLC on β- and γ-cyclodextrins (CD) chiral stationary phases. The quantum chemical calculations of interaction energies of β-CD were carried out for both (R)- and (S)-enantiomers. A high correlation between experimental HPLC data and calculated interaction energies values was obtained.