Charakterisierung von Anionenaustauschern auf Kunstharzbasis durch Pyrolyse-Gas-Chromatographie

Zusammenfassung Die Untersuchungen zur Pyrolyse-Gas-Chromatographie von Ionenaustauschern werden mit 8 Anionenaustauschern auf Kunstharzbasis fortgesetzt. Um vergleichbare und reproduzierbare Pyrogramme aufzunehmen, werden Standardbedingungen erarbeitet, die sich auf die gas-chromatographischen und pyrolytischen Arbeitsbedingungen und die Abmessungen der Trenncapillare beziehen.Die Pyrogramme, die man mit verschiedenen Detektoren (FID, EID, NsFID) erhält, lassen Aussagen über Bau der Matrix, Art und Struktur der funktionellen Gruppen, Beladungszustand, Substitutionsstelle der Ankergruppe an der Matrix und über stereospezifische Substitution zu.Unter Verwendung des vorliegenden Materials eignet sich die Methode zur schnellen Identifizierung von handelsüblichen Ionenaustauschern auf Kunstharzbasis.Die Untersuchungen wurden im Rahmen des SFB 52 Analytik durchgeführt.

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Characterisation of resin-based anion exchangers by pyrolysis gas-chromatography

The studies of ion exchangers by pyrolysis gas-chromatography have been continued with eight anion exchangers on resin basis. In order to obtain comparable and reproducible pyrograms, the gas chromatographic and pyrolytic conditions, and characteristic data of the column capillary have been standardised. The pyrograms obtained with various detectors (FID, EID, NsFID) provide informations about construction of the matrix, type and structure of the functional groups, nature of the anion, position of substitution of the anchor group in the matrix and stereospecific substitution. On using this information, the method is suitable for rapid identification of commercial ion exchangers on resin basis.

     

The influence of the natures of the solvent and coion on the properties of ion-exchange systems

The influence of the coion and the ratio between the water-acetone binary solvent components on cation and anion exchange on sulfo-and aminostyrene ion exchangers with a medium degree of cross-linking were studied. The dependence of selectivity coefficients on the degree of ionite filling by the desired component was found to vary substantially as the composition of the solvent and the radius of the cation changed.     

Charakterisierung von Austauschern mit cyclischen Polyethern als Ankergruppen durch Pyrolyse-Gas-Chromatographie und Pyrolyse-Massenspektrometrie

Zusammenfassung Pyrolyse-Gas-Chromatogramme und Pyrolyse-Massenspektren von Austauschern mit cyclischen Polyethern als Ankergruppen gestatten eine einfache und eindeutige Charakterisierung dieser Polymere. Aussagen über Herstellungsart des Austauschers, Einbau und Art der Ankergruppe sowie Vernetzungsgrad erhält man aus den katalogisierten Fingerprintspektren.Über die vorliegenden Ergebnisse kann der Syntheseweg der Austauscher beurteilt werden. Die polykondensierten Austauscher sind durchweg hoch vernetzt. Die Substituenten eines Hilfsvernetzers beeinflussen den Vernetzungsgrad stark. Substitutionsreaktionen von cyclischen Polyethern mit chlormethyliertem Polystyrol finden höchstens zu 66 % statt. Divinylbenzol ist als Vernetzer für vinylierte cyclische Polyether wenig geeignet. Bei der Polymerisation voluminöser Baugruppen muß ein der Größe angepaßter Vernetzer gewählt werden.

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Characterisation of exchangers with cyclic polyethers as anchor groups by pyrolysis gas-chromatography and pyrolysis mass-spectrometry

Summary Pyrolysis gas-chromatography and pyrolysis mass-spectrometry make possible a simple and definite characterisation of these polymers. The catalogued fingerprint spectra provide information about the method of preparation of the exchanger, the nature and the attachment of the anchor groups to the matrix as well as about the degree of cross-linkage.The results given allow a measurement of the efficiency of the synthesis. All the exchangers produced by polycondensation are highly cross-linked. The degree of cross-linkage is strongly influenced by the substituents of an additional cross-linking reagent. The highest yield for the reaction of cyclic polyethers with chloromethylated polystyrene is 66 %. Divinylbenzene is not suitable as a cross-linking reagent for vinylated cyclic polyethers. For bulky groups a cross-linking reagent of appropriate size has to be used.

Für finanzielle Unterstützung danken wir der Deutschen Forschungsgemeinschaft, Bonn-Bad Godesberg.     

Simple and versatile operational fractionation of Fe and Zn in dietary products by solid phase extraction on ion exchange resins

A simple and versatile protocol, based on use of solid phase extraction on strong ion exchangers and off-line detection by flame atomic absorption spectrometry, was devised to fractionate iron and zinc in common dietary food and beverages products, i.e., bee honeys, fruit juices and tea infusions. In the procedure proposed, cation exchanger Dowex 50Wx4 and anion exchanger Dowex 1x4 were used separately for distinguishing broadly meant the cationic metal fraction and the fraction of stable anionic metal complexes, respectively, after retention of metal species and their exhaustive elution by means of a 4.0 mol l⁻¹ HCl solution. The third fraction, referred to the residual metal species, was retrieved by difference between total soluble metal contents and sum of metal quantities in separated cationic and anionic fractions. The fractionation pattern observed for both metals was described and discussed.     

H+-Ca2+ Equilibrium Exchange on Polyacrylic Cationites

Potentiometric titration curves of carboxyl-containing polyacrylic cation exchangers (Amberlite IRC 86, Dowex MAC 3, Lewatit CNP 80, Purolite C 104, and Relite CNS) in the H form with calcium ions were measured. It was found that the apparent equilibrium constant strongly depended on the composition of resinate solutions, which was indicative of significant deviations of solutions in the cation exchanger gel phase from the ideal behavior. The largest deviations were observed for Dowex MAC 3 ion exchanger, and the smallest, for Amberlite IRC 86. For the other sorbents, the dependences coincided to within measurement errors. The experimental data were treated in terms of six models of the theory of exchange equilibria. The best approximation to titration curves was obtained in terms of the model that suggested the presence of two types of exchange centers in ion exchangers and took into account the influence of the state of three neighboring fixed groups on each spatially separated center. The amounts of centers of all types in the ion exchangers were determined. Differences in the selectivity of the cation exchangers with respect to calcium ions were explained.     

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.     

Effect of gamma radiation on organic ion exchangers

Effects of gamma radiation on indigenous strong cation and anion exchange resins have been studied in HCl medium up to a dosage of 3600 kGy. The ion exchange capacities of cation and anion exchangers decreased by around 20% at 2400 kGy of absorbed dose. Decrease in salt-splitting capacity and total exchange capacity for both cation and anion exchangers were comparable up to 2400 kGy. Above 2400 kGy, a marginal loss in the capacity was observed for cation exchangers whereas a drastic reduction was noticed for the anion exchangers. The distribution coefficients for zirconium, antimony and cobalt, measured in HCl medium, did not change significantly for 2400 kGy of absorbed dose. Crushing strength and moisture retention capacity did not exhibit any specific trend with the absorbed dose.     

Synthesis and chromatographic properties of new polymer-based anion exchangers

New anion exchangers with the trimethylammonium functional group were prepared as a result of three-step synthesis involving the acylation of styrene-divinylbenzene copolymer with 25% cross-linking, the reductive amination of carbonyl groups, and subsequent methylation. Two methods of reductive amination were studied, and optimal conditions for this process were chosen. Chromatographic properties of the adsorbents were examined in a mode of ion chromatography with suppressed background conductivity and conductometric detection. The obtained anion exchangers demonstrated good selectivity, and the maximum efficiency was 30000 TP/m.     

Synthesis of polymeric anion exchangers bearing dimethylhydrazine and alkylammonium functional groups and comparison of their chromatographic properties

A new anion exchanger for ion chromatography bearing an N,N-dimethylhydrazine functional group was synthesized by chloromethylation followed by the amination of a copolymer of styrene and divinylbenzene with a crosslinking degree of 50%. Its chromatographic properties were studied in a two-column mode of ion chromatography with conductometric detection. The anion exchanger obtained is characterized by better selectivity and efficiency than ion exchangers bearing alkylammonium functional groups, namely, trimethylamine, triethylamine, N,N,N′,N′-tetramethyldiaminomethane, N,N,N′,N′-tetramethylethylenediamine, and pyridine. Addition of p-hydroxybenzonitrile in the eluant improved the shape of the peak of the nitrate ion and allowed the simultaneous determination of fluoride, chloride, nitrate, phosphate, and sulfate ions.     

The Chromatographic Behavior of some Hydrophilic Dyes and Dye Intermediates on Thin Layers of Strong and Weak Ion Exchangers

Abstract

The chromatographic behavior of some polar organic dyes and dye intermediates on thin layers of various forms of cationic and anionic exchange resins has been investigated. The results of this study indicate that the stationary ion and the mobile ion of both types of exchangers greatly affect both the level of tailing and the R_f values of the adsorbed compounds. It is also clear from this study that these resins are more suitable for evaluating the relatively simple dyes containing an SO₃Na group than the higher molecular weight polyazo direct dyes used on cellulosic substrates, and that the Li⁺ and H⁺ forms of the cation exchangers work better than their counterparts. On the other hand, cationic dye molecules require the use of anion exchangers, with the ^?OAc form giving better chromatograms than the C104^? form.     

Isolation of transplutonium elements on ion exchangers from solutions of high salt concentration

The behaviour of transplutonium elements (TPE) on cation and anion exchangers in aqueous alcoholic solutions of chlorides and nitrates of some alkali and alkaline earth metals as depending on different factors: salt concentration, content of alcohol and of acid in the solution as well as the nature of a cation has been studied. The data obtained were used to determine the optimal conditions of concentration of TPE on ion exchangers from solutions containing great quantities of salts. The advantages of the use of aqueous alcoholic solutions of nitric acid in the isolation of TPE from such solutions have been shown.     

Anion exchangers functionalized by chelating reagents (AnChel) for preconcentration of trace elements: Capabilities and limitations

Summary Conventional anion exchangers (e.g., Adsorbex SAX, Amberlite IRA 410, Dowex 1X8, Lewatit MP 5080, TEAE cellulose) functionalized by means of sulfonated metal reagents (e.g., Arsenazo III, Eriochrome Red B, 8-hydroxyquinoline-5-sulfonic acid, Tiron and others) were investigated as collectors (AnChel) for analytical preconcentration of trace elements. In particular, the stability of AnChel strongly depending on competing anions, on the anion exchanger and on the metal reagent chosen, was characterized. Accordingly, for appropriate combinations of AnChel (e.g., Dowex 1X8/Arsenazo III) reagent distribution coefficients K_d in the range 10⁴ to 10⁵ (ml/g) could be attained on polystyrene-based anion exchangers even in concentrated salt solutions (e.g., 4 mol/l NaCl), but not on hydrophilic exchangers (e.g., SAX, TEAE cellulose). In general, the stability of AnChel against competing anions followed the order Cl^–>SO ₄ ^2– >NO ₃ ^– >ClO ₄ ^– . Reagent loadings of about 1 mmol/g (e.g., 8-hydroxyquinoline S) on the anion exchangers were obtainable. Trace metals precomplexed with the reagents cited could be separated (>90%) within 5 min and remobilized by acid (e.g. 2 mol/l HNO₃) within some 10 s (batch procedure). Using small columns filled with anion exchanger (e.g., 0.25 g Dowex 1X8) fast trace-matrix separations were carried out with 8-hydroxyquinoline S (Cu, Fe, In, Mn, Pb, Zn) in MgCl₂ solutions and with Arsenazo III (U, Th) in AlCl₃ solution, respectively. For subsequent trace determinations the flame-AAS (injection technique) was applied, except for Th and U [quantified by total reflection X-ray fluorescence (TXRF)].     

The effect of alkylating agent on the efficiency and selectivity of new polymeric anion exchangers

New anion exchangers for ion chromatography with functional groups of trimethylammonium and 3-chloro-2-hydroxypropyl-N,N-dimethylammonium were obtained. The synthesis included consecutive acetylation of a styrene-divinylbenzene copolymer containing 25% divinylbenzene, reductive amination of carbonyl groups, and subsequent alkylation. Iodomethane and epichlorohydrin were used as alkylating agents. The chromatographic properties of anion exchangers were studied by means of suppressed ion chromatography with conductometric detection. Anion exchangers with the 3-chloro-2-hydroxypropyl-N,N-dimethylammonium group are characterized by better selectivity and higher efficiency for polarizable nitrate and bromide ions, as well as for nonpolarizable chloride, fluoride, nitrite, phosphate, and sulfate ions, compared to those of sorbents with the trimethylammonium group.     

Pyrolyse-gas-chromatographische und pyrolyse-massenspektrometrische Untersuchungen an polymeren Kronenethern

Zusammenfassung Pyrolyse-Gas-Chromatographie und Pyrolyse-Massenspektrometrie dienen zur Charakterisierung erstmalig hergestellter Polymeren mit Polyethern als Ankergruppen. Zu den untersuchten Polymeren gehören: mit cyclischen Polyethern und nichtcyclischen Ethern substituiertes Polystyrol, mit cyclischen Polyethern substituiertes Kieselgel und Polykondensate, hergestellt aus cyclischen Polyethern und Vernetzern. Die Pyrolyse-Gas-Chromatogramme zeigen für den jeweiligen Polymertyp charakteristische Spektren und gestatten eine eindeutige Zuordnung der Art der Matrix und Ankergruppen sowie der Verknüpfung von Ankergruppe und Matrix. Die Pyrolyse-Massenspektren liefern schnelle qualitative Aussagen über Zusammensetzung und pyrolytisches Abbauverhalten der Polymeren. Mit den vorliegenden Ergebnissen kann der Syntheseweg von Polymeren mit cyclischen Polyethern als Ankergruppen beurteilt und gegebenenfalls modifiziert werden. Auch eine einfache Identifizierung unbekannter Polymeren ist möglich.

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Pyrolysis gas-chromatographic and pyrolysis mass-spectrometric examinations of polymeric crown ethers

Summary Pyrolysis gas-chromatography and pyrolysis mass-spectrometry are useful to characterize polymers with polyethers as anchor groups, which are synthesized for the first time. The analysed polymers are: polystyrene substituted with cyclic polyethers and non-cyclic ethers, silica gel substituted with cyclic polyethers and polycondensates synthesized from cyclic polyethers and cross-linking reagents. The pyrolysis gas-chromatograms show characteristic spectra for the respective type of polymer and make possible a definite classification of the type of the matrix and anchor groups as well as of the cross-linking of anchor group and matrix. Pyrolysis mass-spectra provide rapid qualitative information on composition and thermal breakdown mechanism of the polymers.The results given allow the evaluation of the efficiency of the synthesis way used for polymers with cyclic polyethers as anchor groups and may be used to modify the syntheses. They also allow a simple identification of unknown polymers.

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Für finanzielle Unterstützung danken wir der Deutschen Forschungsgemeinschaft, Bonn-Bad Godesberg.     

Improved method for the separation of radioactive strontium from various samples by mixed solvent anion exchange

Procedures for the separation and determination of⁹⁰Sr in liquid samples, with cation and anion exchangers have been described. Strontium, yttrium and other cations bind to the cation exchanger and are eluted from the column by means of nitric acid. Separation of yttrium and strontium from other cations is carried out on columns filled with strong base anion exchangers in nitrate form with alcoholic solutions of nitric acid. This separation method enables the determination of⁹⁰Sr through yttrium on a low-level gas flow α, β-counter, as well as through strontium on a lowlevel liquid scintillation counter by means of Cherenkov counting. Such procedures have been tested by the determination of⁹⁰Sr in water, wine, medium radioactive liquid waste samples, milk and clover samples. For comparison, the determination has also been carried out by the standard method. It has been showed that the developed procedures might produce a high efficiency in strontium separation and a satisfactory accuracy of determination.     

Polystyrene immobilized ionenes as novel stationary phase for ion chromatography

Several aliphatic ionenes (2-6-, 6-6-, 10-6-ionene) have been prepared as ion exchangers for the development of novel high-performance stationary phases for anion chromatography (IC). A macroporous polystyrene/divinylbenzene (PS/DVB) resin with adjusted cation exchange capacity was used as support. Therefore the immobilization of ionenes to polystyrene carriers with remaining positive surface charge became possible for the first time. Strong ion-exchange interactions, resulting in high retention times, between the stationary phase and inorganic as well as organic anionic analytes have been observed. The influence of different ionenes on the retention behaviour during the ion chromatographic separation was investigated. Additionally, partly aromatic and polar ionene backbones were prepared and their retention behaviour as anion exchanger was investigated. The highest number of theoretical plates obtained was about 90.000 per meter. The signal asymmetries were generally lower than obtained for surface functionalized anion exchangers.     

Distribution of heteroatoms of synthetic ion exchangers in pyrolysis products

Distribution of sulfur and nitrogen atoms in products of pyrolysis of spent synthetic ion exchangers AV-17 and KU-2 in the temperature range 50–550°C was studied. The compounds containing heteroatoms were identified, and their amounts were determined.     

Pyrolysis—gas chromatography of quaternary ammonium salts in aqueous solution

The pyrolysis of a range of simple quaternary ammonium salts in aqueous solution has been studied by gas chromatographic procedures. The results indicate that the structure of the cation governs the thermal stability and breakdown pattern of the salts, the nature of the anion having no apparent effect on the process. The mechanism of the decomposition is discussed as is the potential of aqueous pyrolysis—gas chromatography for analytical studies of quaternary ammonium salts in general.     

Determination of Ca, Mg, Fe and Zn partitioning in UHT cow milks by two-column ion exchange and flame atomic absorption spectrometry detection

An operationally defined fractionation protocol was developed to study the partitioning of Ca, Mg, Fe and Zn in UHT cow milks. The method was based on sorption of distinct metal species by two ion exchange columns, namely strong cation exchanger Dowex 50Wx4 and strong anion exchanger Dowex 1x4, connected in a series. The evaluation of the donation of metal species classes distinguished, that is cationic and anionic fractions, was made after splitting the columns and elution of metal groupings with a 2.0 mol l⁻¹ HCl solution, followed by the determination of metal concentrations in the resulting eluates. The amount of third, inert fraction was assessed by measuring metal contents in the effluents obtained after passage of the samples through the columns. The results achieved utilizing two-column ion exchange based procedure were compared with those obtained for the approach in which the columns were considered separately. The fractionation pattern for each metal studied was thoroughly discussed in light of available knowledge relating to the composition of milk.