Electrodialysis and electrodeionization are separation processes whose performance depends on the quality and properties of ion-exchange membranes. One of the features that largely affects these properties is heterogeneity of the membranes both on the macroscopic and microscopic level. Macroscopic heterogeneity is an intrinsic property of heterogeneous ion-exchange membranes. In these membranes, the functional ion-exchange component is dispersed in a non-conductive binder. The functional component is finely ground ion-exchange resin particles. The understanding of the effect of structure on the heterogeneous membrane properties and behavior is thus of utmost importance since it does not only affect the actual performance but also the cost and therefore competitiveness of the aforementioned separation processes. Here we study the electrokinetic behavior of cation-exchange resin particle systems with well-defined geometrical structure. This approach can be understood as a bottom up approach regarding the membrane preparation. We prepare a structured cation-exchange membrane by using its fundamental component, which is the ion exchange resin. We then perform an experimental study with four different experimental systems in which the number of used cation-exchange particles changes from 1 to 4. These systems are studied by means of basic electrochemical characterization measurements, such as measurement of current-voltage curves and direct optical observation of phenomena that occur at the interface between the ion-exchange system and the adjacent electrolyte. Our work aims at better understanding of the relation between the structure and the membrane properties and of how structure affects electrokinetic behavior of these systems.
Zwitterionic chiral ion-exchange selectors (ZWIX) obtained by conjugation of quinine and 2-aminocyclohexanesulfonic acid via a carbamate bond were immobilized on three different silica particle types, viz. 120 Å 3 μm fully porous particles (FPP), 200 Å 3 μm FPP and 160 Å 2.7 μm superficially porous particles (SPP). Selector densities were determined by elemental analysis and the porosities of packed columns measured by inverse size exclusion chromatography with polystyrene standards. Liquid chromatographic tests with a set of chiral zwitterionic, acidic and basic analytes showed that the surface chemistry was successfully transferred to the distinct particle morphologies. The chromatographic performance of the three columns was evaluated by acquiring van Deemter curves. The results showed that the column packed with the SPP particles gives the best performance and kinetic plots further demonstrated that they represent the most favorable compromise in terms of speed, efficiency and pressure drop. Sub-minute separations could be accomplished at much lower pressure drop on the core-shell column, e.g. 2-amino-2-phenylbutyric acid was baseline separated in less than 15 s on a 5 cm long column. The Maxwell effective medium theory with second order approximation was applied to calculate effective diffusion in the mesoporous zones of SPP and FPP, which allowed eventually to deconvolute the individual peak dispersion contributions (ha, hb, hc,m, hc,s, hc,ads). The efficiency gain of the 160 Å SPP column compared to the 120 Å FPP (benchmark) column was mainly due to lower eddies (ha), smaller c-term accounting for slow adsorption-desorption kinetics in enantioselective chromatography (hc,ads), and also due to lower stationary mass transfer resistance (hc,s). Enhanced effective diffusion (Deff) in the SPP column contributed to a lower longitudinal diffusion (hb). In contrast, the mobile phase mass transfer coefficient was similar in the two columns leading to comparable hc,m contributions. This study discloses some options for improvement of the efficiency of ZWIX-type chiral columns such as replacing narrow pore (120 Å) by wide pore (200 Å) particles, substituting FPP by SPP and reducing the selector density on the surface.
We assessed the relationship between the diffusive gradient in thin film (DGT) technique using the new ion-exchange resin Ambersep GT74 and the uptake of mercury (Hg) by a model plant cultivated on metal-contaminated agricultural soils under greenhouse conditions. Based on the total Hg content, 0.37 to 1.17% of the Hg passed to the soil porewater from the solid phase, and 2.18 to 9.18% of the Hg is DGT-available. These results were confirmed by calculating the R value (the ratio of the concentrations of bioavailable Hg measured by DGT and soil solution), which illustrated the strong bonding of Hg to the solid phase of soil and its extremely low mobility. Only inorganic Hg2+ species were found in the metal-contaminated agricultural soils, as determined by a high-performance liquid chromatography-cold vapor atomic fluorescence spectrometry speciation analysis. The Hg was distributed in Miscanthus × giganteus organs in the following order for all sampling sites: roots (55-82%) > leaves (8-27%) > stems (7-16%) > rhizomes (4-7%). Environ Toxicol Chem 2019;38:321-328. © 2018 SETAC.
- MeSH
- biologická dostupnost MeSH
- biologické modely MeSH
- biologický transport MeSH
- iontoměniče chemie MeSH
- látky znečišťující půdu analýza metabolismus MeSH
- lipnicovité metabolismus MeSH
- monitorování životního prostředí metody MeSH
- půda chemie MeSH
- rtuť analýza metabolismus MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- chronická renální insuficience farmakoterapie MeSH
- draslík krev MeSH
- hyperkalemie * farmakoterapie prevence a kontrola MeSH
- kationtoměniče terapeutické užití MeSH
- lidé MeSH
- polymery škodlivé účinky terapeutické užití MeSH
- polystyreny terapeutické užití MeSH
- silikáty * škodlivé účinky terapeutické užití MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- přehledy MeSH
We present the enantioseparation of new designer drugs from the cathinone family on structurally different chiral ion-exchange type stationary phases. A novel strong cation-exchange type chiral stationary phase was synthesized and its performance compared with previously reported ion-exchange type chiral stationary phases. The influence of structural elements of the chiral selectors on their chromatographic performance was studied and the possibilities of tuning chromatographic parameters by varying the polarity of the employed mobile phases were determined. Evidence is provided that a change in mobile phase composition strongly influences the solvation shell of the polarized and polarizable units of the selectors and analytes, as well as ionizable mobile phase additives. Furthermore, the structural features of the selectors (e.g. the size of aromatic units and their substitution pattern) are shown to play a key role in the effective formation of diastereomeric complexes with analytes. Thus, we have achieved the enantioseparation of all test analytes with a mass spectrometry-compatible mobile phase with a chiral strong cation-exchange type stationary phase.
- MeSH
- dekontaminace * metody MeSH
- iontoměniče * terapeutické užití MeSH
- lidé MeSH
- nebezpečné látky toxicita MeSH
- Check Tag
- lidé MeSH
The aim of this study was to optimize the preparation of a heterogeneous cation exchange membrane in correlation of measured membrane properties. The membrane was prepared using different loadings and particle size distributions of the resin in polymer matrix. The evaluated membrane properties were ion exchange capacity, water content, real and specific resistance, permselectivity and mechanical properties.
- Klíčová slova
- iontovýměnná membrána, iontovýměnná pryskyřice, distribuce velikostí částic,
- MeSH
- iontoměniče chemická syntéza chemie MeSH
- kationtoměniče * chemická syntéza chemie MeSH
- Publikační typ
- práce podpořená grantem MeSH
- MeSH
- chronické selhání ledvin * dietoterapie komplikace MeSH
- hydrogenuhličitan sodný terapeutické užití MeSH
- hyperfosfatemie farmakoterapie MeSH
- iontoměniče terapeutické užití MeSH
- ketokyseliny terapeutické užití MeSH
- lidé MeSH
- nízkoproteinová dieta * metody MeSH
- pití MeSH
- polyaminy terapeutické užití MeSH
- potrava speciální MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- novinové články MeSH
A novel chlorophyll a containing pigment-protein complex expressed by cells of Chromera velia adapted to growth under red/far-red illumination [1]. Purification of the complex was achieved by means of anion-exchange chromatography and gel-filtration. The antenna is shown to be an aggregate of ~20kDa proteins of the light-harvesting complex (LHC) family, unstable in the isolated form. The complex possesses an absorption maximum at 705nm at room temperature in addition to the main chlorophyll a maximum at 677nm producing the major emission band at 714nm at room temperature. The far-red absorption is shown to be the property of the isolated aggregate in the intact form and lost upon dissociation. The purified complex was further characterized by circular dichroism spectroscopy and fluorescence spectroscopy. This work thus identified the third different class of antenna complex in C. velia after the recently described FCP-like and LHCr-like antennas. Possible candidates for red antennas are identified in other taxonomic groups, such as eustigmatophytes and the relevance of the present results to other known examples of red-shifted antenna from other organisms is discussed. This work appears to be the first successful isolation of a chlorophyll a-based far-red antenna complex absorbing above 700nm unrelated to LHCI.
- MeSH
- aniontoměniče MeSH
- Apicomplexa metabolismus MeSH
- chlorofyl metabolismus MeSH
- chromatografie iontoměničová MeSH
- cirkulární dichroismus MeSH
- fluorescenční spektrometrie metody MeSH
- gelová chromatografie MeSH
- spektrofotometrie ultrafialová metody MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Biogenic amines (BAs) are basic nitrogenous low mass compounds with aliphatic (spermine, spermidine, putrescine, cadaverine), heterocyclic (e.g. tryptamine, histamine) or aromatic (e.g. tyramine) structure derived mainly from the decarboxylation of amino acids 1. They may be formed by the action of yeast, lactic acid bacteria or other microorganisms during alcoholic and malolactic fermentation 2. Most of BAs have strong physiological effects and play important biological role as source of nitrogen and precursors for synthesis of broad spectrum of biomolecules, such as hormones or nucleic acids 3. On the other hand BAs have been widely studied as potentially toxic substances, since excessive intake of BAs manifests as food poisoning 4. Moreover, BAs are potential precursors for the formation of carcinogenic N-nitroso compounds 5. In order to determine the concentrations of biogenic amines in biological matrices, techniques providing high resolution and sensitivity are demanded. To determine BAs is challenging because of strong polarity and no natural UV absorption nor fluorescence. Thus BAs must be pre or post-column derivatized before detection 6. Magnetic separation may be employed for isolation of a sample from complicated biological matrixes (food, body fluids) and may thus form the first separation and pre-concetration step prior to analysis to enhance an applied methodological approach 7. The main aim of the present study is synthesis of nanomaghemite core and its functionalization with ion-exchange resins (Dowex and sulfoxyethyl cellulose), which can provide binding sites for chosen BAs (Tyramine-Tyr; Putrescine-Put; Histamine-His; Cadaverine-Cad, Spermine-Spm and Spermidine-Spd respectively). Synthetic particles were finally employed for isolation and subsequent analysis by using ion-exchange chromatography.
- MeSH
- biogenní aminy * izolace a purifikace MeSH
- celulosa * analogy a deriváty MeSH
- chromatografie iontoměničová statistika a číselné údaje MeSH
- iontoměniče MeSH
- kovové nanočástice * MeSH
- magnetismus MeSH
- syntetické pryskyřice * MeSH
- výzkum MeSH
- železité sloučeniny chemická syntéza MeSH
- Publikační typ
- hodnotící studie MeSH
- práce podpořená grantem MeSH
