Additivity of retention of diastereoisomeric and enantiomeric arylphthalides, aryl(arylene)phthalides and aryldiphthalides of dyadic and triadic composition.

For the first time, four series of new phthalide-containing heteroaromatic compounds were separated by reverse phase HPLC: OYO, OYS, SYS; OYOYO, OYOYS, SYOYS; SYSYS, SYSYO, OYSYO; OYYO, OYYS, SYYS, (where O - diphenyloxide, S - diphenylsulfide, Y - phthalide group). A fundamental difference was established in the chromatographic behavior of diaryl(arylene)diphthalides, built on the principle of "head-to-tail", and diaryldiphthalides with a structure of "head-to-head". The meso and chiral diastereoisomers of the former were eluted by one peak, while the latter existed in solution in the forms of stable cis (racemic form) and trans (meso form) rotamers with different retention times. It was shown that to calculate the retention times of related diarylphthalides, diaryl(arylene)phthalides, diastereoisomeric and enantiomeric diaryldiphthalides of an asymmetric structure, the half-sum rule can be applied according to which: tR(A-X-B)≈[(tR(A-X-A)+tR(B-X-B)]/2. For diaryl(arylene)diphthalides of a triadic structure, a modified additive scheme for calculating retention times is proposed, including multiplication and division operations: tR(A-A-A) = tR(A-A-B) × tR(A-B-B)/tR(B-B-B).

Investigation of the new sorption preconcentration systems for determination of noble metals in rocks by inductively coupled plasma-mass spectrometry.

The reversible sorption preconcentration of noble metals (NMs) prior to their determination by inductively coupled plasma-mass spectrometry (ICP-MS) was investigated. Six new hypercrosslinked polystyrene sorbents were tested. The dependence of the degree of NMs sorption on the average degree of polymer network crosslinking and pore diameters was investigated. It was found that sorbents HP-100/6, HP-300/6 and HP-500/6 have low efficiency of NMs chlorocomplexes extraction. Among Stirosorb sorbents (Stirosorb-2, Stirosorb-514 and Stirosorb-584) the highest efficiency of the extraction of NMs' chlorocomplexes has Stirosorb-514. Tributylamine (TBA), N-methylbenzylamine (MBA), N,N-dimethylbenzylamine (DMBA), N,N-dibenzylmetylamine (DBMA) were studied as the reagents for extraction of Ru, Rh, Pd, Ir, Pt and Au chlorocomplexes from hydrochloric acid solutions in the form of ion associates by reversed-phase mechanism. The reversible quantitative extraction of Ru, Pd, Pt and Au in system Stirosorb-514 - TBA - 1M HCl in ethanol as eluent was achieved. It was found that resulting eluates do not contain matrix components which may cause spectral interferences on the stage of NMs determination by ICP-MS. The found scheme of NMs reversible sorption was validated by the analysis of certified reference materials of basic and ultrabasic rocks GPt-5, GPt-6 and SARM-7. Good agreement between the measured NMs concentrations and the certified values was demonstrated. The achieved limits of detection for Ru, Pd, Pt and Au vary within 10(-8)-10(-7)wt% range.

Selectivity in preparative separations of inorganic electrolytes by size-exclusion chromatography on hypercrosslinked polystyrene and microporous carbons.

Preparative-scale separation of concentrated solutions of simplest mineral electrolytes by size-exclusion chromatography was performed on three samples of commercially available microporous hypercrosslinked polystyrene sorbents "Macronet Hypersol" and two experimental samples of activated carbons. Selectivity of separation of a pair of electrolytes was found to be determined by the largest ions in each pair. Fortunately, selectivity rises at higher concentrations of electrolytes, which was explained by exclusion of smaller species from the concentrated solution, i.e., mobile phase, into small pores of the column packing that are inaccessible to large species. The separation of concentrated mixtures revealed another remarkable advantage of the new process - self-concentrating of each of two separated components in the corresponding fractions. Self-concentration is more pronounced for the minor component that occupied less space in the initial mixture. The new method may prove productive in processing pickle bath solutions.

Elucidation of retention mechanisms on hypercrosslinked polystyrene used as column packing material for high-performance liquid chromatography.

Establishing of basic retention mechanisms was considered the key target during the development of new column packing materials. To extract, from an appropriate retention data matrix on hypercrosslinked polystyrene Chromalite 5HGN, certain factors that can be brought in an obvious correspondence with known retention mechanisms, the principal component analysis (PCA) was applied. The approach was used to elucidate the adsorption properties of the above novel HPLC packing. Besides HPLC, knowledge of retention mechanisms helps to reveal perspective application area for the hypercrosslinked polystyrene-type materials in solid-phase extraction (SPE) and low-pressure preparative LC.

Hypercrosslinked polystyrene as a novel type of high-performance liquid chromatography column packing material. Mechanisms of retention.

An experimental material, Chromalite 5HGN (Purolite, UK), that represents hypercrosslinked polystyrene as a new type of neutral stationary phase for HPLC was examined. The material contains no functional groups, but is compatible with any kind of nonpolar and highly polar mobile phase, and even with water. It is chemically resistant and thermally stable. When using aqueous organic mobile phases, Chromalite 5HGN works similar to standard C18 reversed-phase packings, but is characterized by much greater hydrophobicity and, sometimes, unusual selectivity. When using nonpolar mobile phases, i.e. under "quasi normal-phase" conditions, the retention is mostly governed by the interactions between pi-electronic systems of the adsorbent and adsorbate. Adding highly polar, even hydrophilic solvents into the mobile phase, leads to a shift of retention times toward the "reversed-phase" kind of chromatography, which gives an additional possibility in fine tuning the column selectivity.

Platinum-containing hyper-cross-linked polystyrene as a modifier-free selective catalyst for L-sorbose oxidation.

Impregnation of hyper-cross-linked polystyrene (HPS) with tetrahydrofuran (THF) or methanol (ML) solutions containing platinic acid results in the formation of Pt(II) complexes within the nanocavities of HPS. Subsequent reduction of the complexes by H2 yields stable Pt nanoparticles with a mean diameter of 1.3 nm in THF and 1.4 nm in ML. The highest selectivity (98% at 100% conversion) measured during the catalytic oxidation of L-sorbose in water is obtained with the HPS-Pt-THF complex prior to H2 reduction. During an induction period of about 100 min, L-sorbose conversion is negligible while catalytic species develop in situ. The structure of the catalyst isolated after the induction period is analyzed by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Electron micrographs reveal a broad distribution of Pt nanoparticles, 71% of which measure less than or equal to 2.0 nm in diameter. These nanoparticles are most likely responsible for the high catalytic activity and selectivity observed. The formation of nanoparticles measuring up to 5.9 nm in diameter is attributed to the facilitated intercavity transport and aggregation of smaller nanoparticles in swollen HPS. The catalytic properties of these novel Pt nanoparticles are highly robust, remaining stable even after 15 repeated uses.

30 years of chiral ligand exchange.

The history of the discovery and some benchmark achievements of enantioselective ligand exchange chromatography (LEC) are briefly reviewed. Some of the most important results of investigations into the structure of Cu(II) complexes with nitrogen-substituted alpha-amino acids are summarized, and the role of water molecules that are coordinated in two axial positions of these complexes in the mediation of between-ligand interactions is underlined. UV and circular dichroism spectroscopy are shown to be very convenient for studying and quantifying the thermodynamic and kinetic enantioselectivity phenomena in the complex formation. Polystyrene-based chiral ligand exchange resins served as the first highly selective column packing in the development of enantioselective liquid chromatography. These resins were then followed by more efficient silica bonded monomeric and polymeric HPLC phases. The latter proved to be especially stable in aqueous media at elevated temperatures. Finally, chiral coated ligand exchanging RP phases presented the most inexpensive, but highly efficient and selective phases for the resolution of chelate-forming racemic solutes in LC and TLC. The mechanism of chiral resolution on these last phases involves an essential interaction of both the selector and selectand with the achiral hydrophobic surface. The same is valid for chiral resolutions according to chiral mobile phase techniques. Perspectives on further development of enantioselective LEC are discussed.

Evaluation of a hypercrosslinked polystyrene, MN-200, as a sorbent for the preconcentration of volatile organic compounds in air.

Breakthrough volumes, average percentage recoveries, and storage stabilities were obtained for vapors of 8 volatile organic compounds (pentane, octane, undecane, isooctane, cyclohexane, toluene, methanol, and dichloromethane) on a new adsorbent material, Hypersol-Macronet, MN-200. Breakthrough volumes were estimated as half of the gas chromatographic specific retention volumes at 20 degrees C for the compounds. Recoveries of the adsorbates were determined by both solvent extraction and thermal desorption methods. The results obtained compare favorably with those for Tenax GR (values reported in the published literature and others obtained in our laboratory). Results of storage stability studies on MN-200 meet the criterion for acceptability (<10% loss). High adsorption capacity for very volatile and polar compounds, combined with ease of desorption of less volatile compounds, render MN-200 a highly promising adsorbent for sampling volatile organic compounds in indoor and outdoor air.

Novel polymeric solid-phase extraction material for complex biological matrices. Portable and disposable artificial kidney.

The replacement of conventional hemodialysis treatment for a patient with malfunctioning kidneys by providing him/her with a portable and disposable "artificial kidney" which is connected to implanted artery and veneous cannulas on a patient's wrist is discussed. During a continuous flow of blood, plasma diffuses through a plasmapheretic membrane, passes through a bed of plasmacompatible sorbent Styrosorb, and arrives at an ultrafiltration membrane. Vacuum-operated ultrafiltration removes excess water together with dissolved urea and other small molecules, and Stryosorb removes medium-sized toxic substances. The hemocompatibility of the sorbent is improved by chemical modification of the surface.

Mass-spectrometric analysis of N-acetylchitooligosaccharides prepared through enzymatic hydrolysis of chitosan.

A semipreparative scale chromatography of N-acetylchitooligosaccharides (GlcNac)2-7 on a reversed-phase C-16 HPLC column is reported. The initial material was obtained by enzymatic hydrolysis of chitosan with a complex of chitinases from Streptomyces kurssanovii, followed by a complete acetylation of amino groups. Isolated N-acetylchitooligosaccharides were characterized by the mass-spectrometric method. On interacting with the sample, the fragments of 252Cf caused desorption of quasi-molecular ions of the substance. All mass spectra of chitin oligomers contained intense quasi-molecular ions [M + Na]+ and a less intense [M + K]+ ion. Fragment ions, compared to the quasi-molecular ion [M + K]+, had a lower intensity and confirmed the structure of samples under study. Due to this phenomenon, an accurate analysis of both individual compounds and mixtures of N-acetylchitooligosaccharides (n = 2-7) may be performed.

One-step isolation of a chitinase by affinity chromatography of the chitinolytic enzyme complex produced by Streptomyces kurssanovii.

One of the four chitinases with a molecular mass of 42 kDa existing in the chitinolytic enzyme complex produced by Streptomyces kurssanovii was separated in homogeneous form using one-step affinity chromatography on cross-linked and phosphorylated chitin-type sorbents. Three other chitinases were not selectively bound by the sorbents and were not obtained in homogeneous form. The affinity sorbents were shown to be stable over the time of separation and could be used repeatedly.

Chitinolytic digestibility of cross-linked chitosan gels by an enzyme complex from Streptomyces kurssanovii.

The action of a microbial chitinolytic enzyme complex from Streptomyces kurssanovii on chitosan gels with various degrees of cross-linking and on the O-derivatives of the gels was examined. The rate of digestion of the gels was shown to depend on the degree of cross-linking as well as on the size of the O-substituent, decreasing greatly with a rise in substitution.

Ion-exchange high-performance liquid chromatography of nucleotides and polypeptides on new types of ion-exchange sorbents, based on polystyrene-coated silicas.

A novel type of ion exchanger was prepared by multipoint covalent binding of polystyrene chains onto the surface of porous silica followed by polymer-analogous modification of the bonded layer. Both anion and cation exchangers were synthesized and examined in the separation of nucleotides and proteins. Rapid and efficient separation of basic polypeptides on strong anion exchangers and that of acidic polypeptides on strong cation exchangers could be achieved. For the separation of complete mixtures of polypeptides the application of zwitter-ionic ion exchangers can be recommended.

[Ligand-exchange chromatography of proteins and enzymes]. / Ligandoobmennaia khromatografiia belkov i fermentov.

Current state of the ligand-exchange chromatography (metal chelate affinity chromatography) of proteins and enzymes is reviewed. This technique is based on the ability of proteins to bind metal ions immobilized on chelate gels. The influence of pH, composition of buffer, type of stationary ligand and nature of metal ions on the chromatographic behaviour of proteins is discussed.

A vivid model illustrating chiral recognition induced by achiral structures.

If diastereomeric complexes are adsorbed on a surface or if they include a molecule of solvent, two points of attractive interaction between the chiral species of the complex can be sufficient for mutual chiral recognition of these species. In special cases even one single point of interaction is sufficient. This extension of the three-point contact rule of Dalgliesh, first observed in chiral ligand-exchange chromatography, can be demonstrated by using hands.

[Immobilization of proteolytic complexes on pectin-containing carriers]. / Immobilizatsiia proteoliticheskikh kompleksov na pektinsoderzhashchikh nositeliakh.

A number of sorbents were synthesized on the basis of pectin and then used for immobilization of proteolytic complexes--pancreatin and protosubtilin. The best properties were shown by the enzyme preparations based on pectin, formaldehyde and melamin (PFM). Thus immobilization of pancreatin on PFM through Fe(III) ions gave a preparation with the activity of 79 000 mumole/g X h with respect to methyl ester of L-tryptophane (the activity yield is 91%). The pH optimum for all immobilized preparations was shifted towards the alkaline region. The thermostable fraction of the immobilized preparations retains the activity at 60 degrees for a long time.

[Coordination-ionic enzyme immobilization. Dependence of properties of immobilized preparations of penicillinamidohydrolase on the nature of metal ion and stationary ligand]. / Koordinatsionno-ionnaia immobilizatsiia fermentov. Vliianie metalla i statsionarnogo liganda na svoistva immobilizovannykh preparatov penitsillinamidogidrolazy.

Penicillinamidohydrolase was immobilized on heteroporous polystyrene supports containing groups of ethylenediamine, diethylenetriamine and triethylenetetramine, using Co(II), Ni(II), Cu(II), Fe(III), Co(III) ions. The effects of substrate concentrations and pH on the activity of the immobilized enzyme were investigated and the kinetic parameters of hydrolysis were determined, using N-phenacetylphenylglycine as substrate. The enzyme immobilization resulted in a slight decrease of Km(app), while the values of V decreased by a factor of two. Preparations possessing high thermal stability were obtained by oxidation of Co(II) to Co(III) in the enzyme sorption complex. High stability was also found for the Fe(III)-containing preparations.

[Hydrolysis of N-acetyl-L- and N-acetyl-D,L-methionine by microbial aminacylase]. / Gidroliz N-atsetil-L i N-atsetil-D,L-metionina mikrobnoi aminoatsilazoi.

The kinetics of N-acetyl-L- and N-acetyl-D,L-methionine hydrolysis by aminoacylase from Asp. oryzae were studied. The maximal rate of the reaction was found to be about 2000 mu moles of L-methionine per mg of protein per hour; Km was equal to about 1.10(-1) M for both the racemic and optically active substrates. In the presence of Co(II) ions (the molar ratio of N-acetyl-L-methionine/Co(II) was 100:1) the reaction velocity was increased. The values of approximately 4500 and approximately 3000 mu moles per mg per hour were-attained with L-enantiomer and racemic substrates, respectively. The Km values were decreased down to 2.10(-2) M and 1.4.10(-2) M, respectively.

Potentiometric determination of the dissociation constants of an asymmetric sorbent containing l-proline, and the stability constants of its Cu(II) complexes.

The dissociation constants of the carboxyl groups (pK(a1) = 2.2, n = 1.8) and amino groups (pK(a2) = 9.5, n(2) = 1.6) of a sorbent prepared by reacting l-proline with a cross-linked chloromethylated styrene polymer have been determined by potentiometric titration. The potentiometrically measured stability constants of the Cu(II) complexes of the resin (logbeta(1) = 6.9 and log beta(2) = 12.4) were found to be close to the values for the Cu(II) complexes of N-benzyl-l-proline. For complexed resins of alpha-amino-acid type the pH-values of decomplexation do not appear to be directly correlated with the stability constants.

Determination of stability constants of fixed-site complexes of copper(II) ions and of sorbed copper-l-proline complexes with an asymmetric resin containing l-proline groups.

By study of the distribution of copper(II) and l-proline (Pro) ions between an aqueous phase and a resin phase with l-proline groupings on a polystyrene matrix (R ), the conditional stability constants of fixed-site R (2) Cu and sorbed R CuPro complexes have been determined and a method for calculation of the constants for alkaline and neutral media is proposed. The values obtained reflect the actual behaviour of the system, and strongly depend on the ph and the ionic strength of the solution in equilibrium with the resin phase. It was established that this dependence and the high values of the conditional constants of complex formation in comparison with the stability constants of low molecular-weight model compounds are due to the donnan distribution of the low molecular-weight participants and to the effect of the electrostatic field of the polyanion. The distribution of the fixed-site ligands on the resin causes considerable differences in the stability of individual fixed-site R Cu complexes and their capacity to enter into reactions with ligands in the aqueous phase.