Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: chromatografia wykluczania jonowego

Sortuj według:

Ogranicz wyniki do:

Chromatografia wykluczania jonowego : mechanizm retencji, przykłady praktycznego zastosowania

Głód B. K.

Wiadomości Chemiczne

2003

[Z] 57, 1-2

115--133

Ion exclusion chromatography (IEC) is applied mostly to separate ionic compounds from the non-ionic ones. Wheaton and Bauman were first to describe this technique in 1953 [1]. At present about 10% of all ion chromatographic determinations are performed using IEC and this is approximately the number of determinations using the more common technique of ion pair (ion interaction) chromatography [2-6]. In the recent years the number of IEC determinations displays a strong tendency to increase. The characteristic feature of IEC technique is the electric charge sign of dissociated ion-exchange resin functional groups that is the same as the electric charge sign of the analyzed ionic compound. It follows that samples of negatively charged ions e.g. dissociated acidic compounds are separated on cation exchange resins with anionic functional groups. Usually these are sulphonic acid groups. Similarly, samples containing positively charged species (bases) are separated on the anion exchange resin containing cationic functional groups. Usually these are tetraalkylammonium groups [2, 6]. In a sense these rules are in contrast to those of ion exchange chromatography, where anions are separated on anion exchange resins and cations are separated on cation exchange resins. However, the same columns can be used in both techniques. For the specific requirements of ion exclusion chromatography large ion exchange capacity is preferential [2, 9]. Along with these, to increase the capacity the column dimensions and the functional group concentration in the support are maximized. The usual supports are based on the macro-porous styrene and divinylbenzene copolymer. IEC finds application in the separation of a wide range of small, neutral or partially ionized molecules. In IEC the strong as well as weak electrolytes are eluted unseparated, the first at the beginning and the latter at the end of the elution. The retention volumes of the remaining electrolytes were found to be proportional to their dissociation constant values. The dead and inner volumes of the chromatographic column can be determined from the observed dependence of retention volumes onto dissociation constant values. The retention mechanism is described by the analytical equations and on the results obtained from the computer simulation of the column performance (using global thermodynamic and chromatographic equations or the Craig method). The mixed retention mechanism involving hydrophobic adsorption, p-electron interactions and screening effect is observed for weak electrolytes and aromatic compounds [8, 13, 14]. Aromatic compounds are retained almost solely involving interaction of the solute with the unfunctionalized regions of the stationary phase. The purpose of this paper is to survey the field. The retention mechanism of analyzed compounds in ion-exclusion chromatography has been described. The influence of some physicochemical parameters describing the sample, the chromatographic column and the mobile phase on the retention is discussed. Finally, practical applications are briefly presented.

Modified analytical method for hydroxyl radicals using spin trapping and ion exclusion chromatography

Głód B. K., Grieb P.

Chemia Analityczna

2002

Vol. 47, No. 3

399-407

Ion exclusion chromatography (IEC) is the predestinated chromatographic technique for weak acids separation and analysis. Preliminary results are presented concerning the application of IEC to the determination of hydroxyl free radicals with the use of hydroxybenzoate spin trapping. Products of the reaction, dihydroxycarboxylic acids, are retained due to the mixed ion exclusion and PI-electron interaction retention mechanism. The method was applied to the determination of hydroxyl radical trapping potential of some organic solvents, phenylacetates, and biogenic polyamines. The later were found to scavenge efficiently hydroxyl radicals, which property may contribute to their cyto- and neuroprotective properties.

Chromatografia wykluczaniajonowego jest dogodną techniką do rozdzielania i oznaczania słabych kwasów. Wstępne wyniki badań wykazały przydatność tej techniki do oznaczania wolnych rodników hydroksylowych po ich pulapkowaniu spinowym hydroksybenzoesami. Mechanizm retencji produktów reakcji, kwasów dihydroksykarboksylowych, jest mieszany, jonowo-wykluczający i związany z Pi-elektronowym oddziaływaniem pierścieni aromatycznych z żywicą. Opracowaną metodę zastosowano do oznaczania potencjału antyoksy-dacyjnego niektórych rozpuszczalników organicznych i poliamin biogennych. Okazało się, że poliaminy są efektywnymi zmiataczami rodników hydroksylowych co może tłumaczyć ich cyto- i neuroprotekcyjne właściwości.