Polyalkyl methacrylate block sorbents for ion chromatography

A number of block anion-exchanges were prepared on basis of polyalkyl methacrylates with a degree of crosslinking 26% and an ion capacity in the range 0.01–0.52 meq/g using 2-(N,N-dimethylamino)ethyl methacrylate and trymethylamine as aminating agents. How the performance and composition of the reaction mixture influence the hydrodynamic properties and ion capacity of the sorbents formed is discussed. Two different ways of incorporating active anion exchange of amino groups are compared: direct synthesis of triple copolymers containing amino groups by means of thermal radical polymerization, and modification of a preformed polyalkyl methacrylate block matrix by reaction with trimethylamine. The selectivity and efficiency of the sorbents were tested for the separation of a number of inorganic and organic anions by ion chromatography with detection by a conductometer.     

Monolithic polymeric sorbents for high-performance chromatography of synthetic polymers

A number of macroporous monolithic materials based on copolymers of butyl methacrylate or lauryl methacrylate with ethylene glycol dimethacrylate is obtained via thermal free-radical polymerization. The effect of polymerization conditions on pore parameters of the synthesized sorbents is studied. Polymer stationary phases obtained for the efficient analysis of synthetic polymers are tested for the separation of a multicomponent mixture containing polystyrene samples of various molecular masses.     

Polyelectrolyte sorbents based on aliphatic ionenes for ion chromatography

2-4, 3-4, 2-8, 3-8, 3-6, 4-6, 6-8, 6-10-ionenes (polymers with quaternary nitrogen atoms in the main chain) served as modifiers in synthesizing polyelectrolyte sorbents for ion chromatography. The approaches to the synthesis and their stability are discussed. Cluster analysis was applied to separate aliphatic ionenes to three groups as chromatographic modifiers, namely hydrophilic, hydrophobic, and intermediate. Each group is characterized by a certain selectivity to sulfate, perchlorate, iodide and thiocyanate. The sorbents show high selectivity and efficiency up to 15 000 theoretical plates per meter.     

Anion chromatography on hydroxyethyl methacrylate-based sorbents

The selectivity of sorbents plays an important role in the design of ion chromatographic separations. The selectivity of the hydroxyethylmethacrylate-based sorbent Tessek Separon HEMA-S 1000 Q-L was compared with those of other commonly used sorbents and the role of the eluent charge was investigated. The selectivity of this sorbent was found to be satisfactory for most commonly used ion chromatographic detection modes, including indirect photometry and both suppressed and non-suppressed conductivity detection.     

Microcolumn liquid chromatography on carbon sorbents

Summary The retention volume dependences on the molar volume were found for aromatic compounds using liquid microcolumn chromatography. The contributions of the functional groups in molecules of these compounds to the total retention value were calculated from the capacity factor values. The comparison of capacity factor values for carbon sorbents and octadecyl-silicagel has shown that for several microcolumn separations the carbon sorbent column has a better selectivity and resolution than the octadecyl-silicagel column.     

Computer optimization of multi-component sorbents in chromatography

Development of multi-component sorbent chromatography has been hampered by the difficulty of choice of optimum composition for a given analysis. The authors have previously presented a computer-based strategy for binary mixtures and now describe an extension which allows a choice of optimum mixture composition to be made from up to five sorbent components comprising the stationary phase. The computer program, DIACHOR, is described and shown, in a comparative study, to be superior to the best alternative previously reported in the literature.     

Functional crown ether derivatives as sorbents for ligand exchange chromatography

Two kinds of macrocyclic compounds, S-TAROH18C6 and S-TAROEt12C4 derived from tartaric acid have been synthesized. The structure and conversion of functional groups on this silica gel based resin have been confirmed by IR spectral and elemental analysis. The coordination behaviour of these materials has been investigated by means of IR, EPR, potentiometry and the modification of Langmuir isotherm equation. The metal complexes have been investigated as stationary phases for the separation of amino acid mixtures. Factors affecting the retention and the sample selectivity have been examined. S-TAROEt12C4 possesses good chromatographic characteristics and a unique selectivity in separating underivatized amino acid mixtures and can be used as well for enantiomeric separations.     

Functional crown ether derivatives as sorbents for ligand exchange chromatography

Two kinds of macrocyclic compounds, S-TAROH18C6 and S-TAROEt12C4 derived from tartaric acid have been synthesized. The structure and conversion of functional groups on this silica gel based resin have been confirmed by IR spectral and elemental analysis. The coordination behaviour of these materials has been investigated by means of IR, EPR, potentiometry and the modification of Langmuir isotherm equation. The metal complexes have been investigated as stationary phases for the separation of amino acid mixtures. Factors affecting the retention and the sample selectivity have been examined. S-TAROEt12C4 possesses good chromatographic characteristics and a unique selectivity in separating underivatized amino acid mixtures and can be used as well for enantiomeric separations.     

Synthesis and application of sorbents for affinity chromatography of serine proteases

Summary A synthetic peptide derivative,—alanyl-alanyl-leucylmorpholide, (Ala-Ala-Leu-N(CH₂CH₂)₂O), is suggested as a specific ligand for affinity chromatography of subtilisin-like serine proteases that prefer hydrophobic amino acid residue in P1 position of their substrates. Z-Ala-Ala-Leu-N(CH₂CH₂), a weak and reversible inhibitor of serine proteases, was synthesized by the carbodiimide method. Affinity sorbents were prepared by coupling the synthesized pepitide derivates to CH or AH Sepharose. Serine proteases from different sources were purified up to 17 fold on these sorbents with yields varying from 25% to 100%. Three enzymes (serine protease X, kallikrein and leucine aminopeptidase) were isolated from urine of children with glomerulonephritis with yields of 57, 22 and 55%. Proteolytic enzymes from the dandelion root, Kamchatka crab and culture filtrates of different microorganisms were also purified on the affinity sorbents. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996.     

Carbonaceous sorbents for high‐temperature interactive liquid chromatography of polyolefins

The elution behavior of polyethylene (PE) and the three stereoisomers of polypropylene (PP) was studied on porous graphite along with three other carbon‐based sorbents, carbon‐clad zirconia particles, activated carbon, and exfoliated graphite in a systematic way in this work. Decahydronaphthalene, 1,2,3,4‐tetrahydronaphthalene, 1,3,5‐trimethylbenzene, tetrachloroethylene, xylene and p‐xylene were used as mobile phases. While PE is adsorbed to various extents on all the tested carbonaceous sorbents from the majority of the solvents, PP is fully adsorbed only in selected cases. Testing alcohols (C7–C9) as mobile phase with Hypercarb? indicates that all stereoisomers of PP are selectively adsorbed and desorbed when a solvent gradient alcohol→1,2,4‐trichlorobenzene is used at 160°C. The retention of all stereoisomers of PP increases with the polarity of the alcohol. Linear PE is retained on Hypercarb? even from 1,2‐dichloro‐ and 1,2,4‐trichlorobenzene, when a temperature below 120°C is applied, while it is not retained from these solvents at higher temperatures. All stereoisomeric forms of PP are not adsorbed under the same conditions. Some of the tested new sorbent/solvent systems have potential to be applied in routine analysis of industrially synthesised polyolefins.     

Characterization of polyimide sorbents by using tracer pulse chromatography

A modification of tracer pulse chromatography was used to rapidly evaluate four novel polyimide sorbents for use in air sampling. This technique utilized probe molecules with differenet functional groups to evaluate the surface retention characteristics when the sorbents were highly loaded by these chemicals and humidity. The evaluation of sorbents indicated the polymer subunits of each must have multiple sorption sites which is consistent with their chemical makeup. Some comparisons between the polyimides and Tenax-GC were made.     

Development of principles of controlled synthesis of monolithic polymeric sorbents for ion chromatography

A series of monolithic macroporous sorbents based on glycidyl methacrylate and ethylene glycol dimethacrylate were prepared by free radical copolymerization. The effect of polymerization conditions and composition of reaction mixture on the pore structure of the monolithic material was studied by IR spectroscopy, intrusion mercury porosimetry, and scanning electron microscopy.     

The preparation of sorbents for the analysis of human antithrombin III by means of high performance affinity chromatography

Summary Antithrombin III (AT III) is an anticoagulant present in blood. It is responsible among other things for blood coagulation and the wrong amount can lead to various health problems. The level of AT III can be taken as an indicator of many pathological states. Due to the very complex composition of blood, high performance affinity chromatography seems to be one of the best methods for the quantitative determination of AT III. The present paper deals with the preparation and properties of sorbents for AT III analysis. The behaviour of the chromatographic packings obtained by the bonding of heparin (used as a complementary ligand interacting with AT III) to cross-linked polysaccharide layers deposited on controlled porosity glass is discussed.     

Nonlinear gas chromatography as a way of studying inhomogeneous sorbents

A way of organizing and processing the results from gas–chromatographic experiments to obtain chromatographic retention characteristics for a fixed concentration of sorbate in the gas phase or on the surface of the sorbent is proposed and substantiated. The suitability and expediency of such retention characteristics for describing the sorption properties of inhomogenous sorbents is demonstrated using a wide variety of adsorbents of different natures (activated carbons, swelling and nonswelling polymers, silicas and their silver derivatives) as examples.

     

The structure of sorbents based on thermally activated iron-containing water preparation precipitate

The structural-phase states of iron oxides and oxyhydroxides, the mean size of nanocrystallites, and microdistortion in nanocrystallite crystal lattices in samples of nanostructured sorbents based on thermally activated precipitate formed in the removal of iron from groundwater were studied by X-ray diffraction and transmission electron microscopy. Some magnetic characteristics of these sorbents were determined.     

A simple model for the structure of fractal aggregates

Structural properties of small aggregates containing up to 100 particles have been studied through detailed Monte Carlo cluster-cluster aggregation simulations in both diffusion-limited and reaction-limited conditions. First, the radius of gyration, the radius of the smallest sphere encompassing the cluster, and the particle-particle correlation function, g(r), have been computed based on the positions of all the particles in the cluster, and their fractal scaling has been analyzed. Then, an empirical model has been developed to simulate the g(r) function for aggregates of any size and used to determine the corresponding structural properties and scattering structure factors. Finally, in order to illustrate the application of the structural properties thus computed, two experiments on diffusion-limited aggregation have been performed, and the average scattering structure factors have been measured as a function of time using a small-angle light-scattering device. The obtained average scattering structure factors have been simulated using the Smoluchowski population balance equations, using the single aggregate structural properties and scattering structure factor predicted by the developed empirical g(r) model.     

Carbon‐based sorbents in chromatography. New achievements

The newest results in the employment of carbon‐based composites in various chromatographic techniques such as gas–liquid chromatography, high‐performance liquid chromatography and electrically driven separation techniques for the separation, quantitative determination and identification of a wide variety of compounds in complicated matrices are compiled. The results are concisely described and critically evaluated. The future trends in the application of carbon‐based compounds in the chromatographic separation methods are briefly discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Mass transfer effects in preparative chromatography of eremomycin on polymeric sorbents

This work is devoted to the study of the regularities of the sorption of the new antibacterial antibiotic eremomycin on carboxylic sorbents. The main sorption kinetic equilibrium and dynamic parameters for realization of one-act preparative chromatographic process were determined and the difference between gel-like and structurally segregated carboxylic cation exchangers was analyzed. The optimal conditions for sorption and complete desorption of eremomycin were found.