Strongly Basic Anion Exchangers

Dowex 1-X2 0.6 0.65 Strongly basic anion exchanger with S-DVB matrix for separation of small peptides, nucleotides, and large metal complexes. Molecular weight exclusion is <2700. 

The symbol R3N represents the complex weakly basic anion-exchanger radical. The symbol R,N represents the complex strongly basic anion-exchanger radical. 

The pH of 1.2 liters of filtrate containing 3.B mg/ml of cytidine diphosphate choline, obtained by removing solid matters from the culturing liquor, was adjusted to a pH of B.5 with a 0.5N KOH solution. The filtrate was passed through a column of strongly basic anion exchange resin, Dowex 1 x 2 (formic acid type). After washing the resin with water, a formic acid... 

Strongly basic anion exchange resins, e.g. a cross-linked polystyrene containing quaternary ammonium groups, are largely ionised in both the hydroxide and the salt forms. Some of their typical reactions may be represented as ... 

Strongly basic anion exchangers (polystyrene quaternary ammonium resins). These resins (Duolite A113, Amberlite 400, etc.) are usually supplied in the chloride form. For conversion into the hydroxide form, treatment with 1M sodium hydroxide is employed, the volume used depending upon the extent of conversion desired two bed volumes are satisfactory for most purposes. The rinsing of the resin free from alkali should be done with de-ionised water free from carbon dioxide to avoid converting the resin into the carbonate form about 2 litres of such water will suffice for 100 g of resin. An increase in volume of about 20 per cent occurs in the conversion of the resin from the chloride to the hydroxide form. 

Anion exchange resin. Proceed as in the previous experiment using 1.0 g, accurately weighed, of the air-dried strongly basic anion exchanger (e.g. Duolite A113, chloride form). Fill the 250 mL separatory funnel with ca 0.25M sodium nitrate solution, and allow this solution to drop into the column at the rate of about 2 mL per minute. Collect the effluent in a 500 mL conical flask, and titrate with standard 0.1M silver nitrate using potassium chromate as indicator. 

Theory. Cadmium and zinc form negatively charged chloro-complexes which are absorbed by a strongly basic anion exchange resin, such as Duolite A113. The maximum absorption of cadmium and zinc is obtained in 0.12 M hydrochloric acid containing 100 g of sodium chloride per litre. The zinc is eluted quantitatively by a 2M sodium hydroxide solution containing 20 g of sodium chloride per litre, while the cadmium is retained on the resin. Finally, the cadmium is eluted... 

Of greatest interest for PAN modification with the purpose of obtaining strongly basic anion-exchange polymers can be the quartemary salts of vinyl pyridines. 

In 1992, Oda et al. reported a one-pot synthesis of optically active cyanohydrin acetates from aldehydes, which were converted to the corresponding racemic cyanohydrins through transhydrocyanation with acetone cyanohydrin, catalyzed by a a strongly basic anion-exchange resin [46]. The racemic cyanohydrins were acetylated by a lipase from P. cepacia (Amano) with isopropenyl acetate as the acyl donor. The reversible nature of the base-catalyzed transhydrocyanation enabled continuous racemization of the unreacted cyanohydrins, thereby effecting a total conversion (Figure 4.21). 

Very pure preparations are obtained by treatment of L-aspartic acid loaded strong basic anion-exchange resins with an aqueous solution of L-arginine hydrochloride. 

To date, a few methods have been proposed for direct determination of trace iodide in seawater. The first involved the use of neutron activation analysis (NAA) [86], where iodide in seawater was concentrated by strongly basic anion-exchange column, eluted by sodium nitrate, and precipitated as palladium iodide. The second involved the use of automated electrochemical procedures [90] iodide was electrochemically oxidised to iodine and was concentrated on a carbon wool electrode. After removal of interference ions, the iodine was eluted with ascorbic acid and was determined by a polished Ag3SI electrode. The third method involved the use of cathodic stripping square wave voltammetry [92] (See Sect. 2.16.3). Iodine reacts with mercury in a one-electron process, and the sensitivity is increased remarkably by the addition of Triton X. The three methods have detection limits of 0.7 (250 ml seawater), 0.1 (50 ml), and 0.02 pg/l (10 ml), respectively, and could be applied to almost all the samples. However, NAA is not generally employed. The second electrochemical method uses an automated system but is a special apparatus just for determination of iodide. The first and third methods are time-consuming. 

Trace amounts of molybdenum were concentrated from acidified seawater on a strongly basic anion exchange resin (Bio-Rad AG1 X-8 in the chloride form) by treating the water with sodium azide. Molybdenum (VI) complexes with azide were stripped from the resin by elution with ammonium chlo-ride/ammonium hydroxide solution (2 M/2 M). Relative standard deviations of better than 8% at levels of 10 xg per litre were attained for seawater using graphite furnace atomic absorption spectrometry. 

Kulprathipanja, S. (1989) Separahon of dtric add from fermentafron broth with a strongly basic anionic exchange resin adsorbent. U.S. Patent 4,851,574. 

Anion exchange is an effective way of removing nitrate and nitrite ions, should these be present at objectionable levels. If a strongly basic anion-exchange resin R4N+OH is used, silica will also be removed as (HOfjSiO-(see Section 7.6), leading to water of low total dissolved solids content ... 

To protect the cation-exchange bed from particulate matter, the original parfait system had a bed of silica gel ahead of the cation-ex-change bed. To neutralize the acid released from the cation bed, as well as to remove anions, a strongly basic anion-exchange bed was added after the cation exchanger. 

A measured volume of extract was passed through a strongly basic anion exchanger (Table 26-1) in the Cl form. Then the resin was washed with distilled water. Liquid containing Cr(III) from the extract and the wash was discarded. 

Strongly basic anion exchange Quaternary ammonium polystyrene 0-12 Anions, halogens, alkaloids, fatty acids... 

TEVA-Resin is an extraction-chromatographic material based on Aliquat 336, which is a liquid quaternary ammonium salt, as described previously in connection with "Tc separations.30 It acts as a strongly basic anion-exchange material, retaining tetravalent actinides from 2-4 M HN03 solutions as anionic nitrato complexes (see Figure 9.11). Am(III), Np(V), and U(VI) are much less retained. The extraction... 

Niederer [100] used ion trap mass spectrometry and negative ion chemical ionisation to determine nitro- and oxypolyaromatic hydrocarbons in soils. Meyer et al. [101] have described a simple and reproducible method which provides the simultaneous determination of polycyclic aromatic hydrocarbons and het-eropolycyclic aromatic hydrocarbons (N, S, O) and their metabolites in contaminated soils. Contaminants extracted from the soil sample were separated by polarity and acid-base characteristics using solid-phase extraction on silica gel and a strong basic anion exchange material. A subfraction containing PANHs and neutral metabolites was subsequently fractionated into neutral and basic... 

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