Anion-exchange, chloride column resin

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. 

Procedure. Prepare a column of the anion exchange resin using about 15 g of Duolite Al 13 in the chloride form (Section 7.9). The column should be made up in 2 M hydrochloric acid. 

Theory. The anion exchange resin, originally in the chloride form, is converted into the nitrate form by washing with sodium nitrate solution. A concentrated solution of the chloride and bromide mixture is introduced at the top of the column. The halide ions exchange rapidly with the nitrate ions in the resin, forming a band at the top of the column. Chloride ion is more rapidly eluted from this band than bromide ion by sodium nitrate solution, so that a separation is possible. The progress of elution of the halides is followed by titrating fractions of the effluents with standard silver nitrate solution. 

As mentioned in the historical synopsis (Section 5.1), Levine121 perfected the compendial partition column procedure in which aspirin in chloroform is first trapped in an immobile phase of sodium bicarbonate on a column of siliceous earth (celite) then eluted with a solution of acetic acid in chloroform and measured spectrophotometrically. This has been also used for separation in combination products.80 For the determination of salicylic acid in presence of aspirin by this method, see Section 5.61. Ion exchange columns filled with strongly or weakly basic anion exchange resin in the acetate or chloride cycle have also been used for separation of aspirin in combination products. 122 123/l2lf This has also been adapted for a student experiment.125 A Sepha-dex-G25 column has been used for the separation of aspirin from salicylic acid.126... 

The decomposition products were separated by eluting with potassium chloride solution on a column packed with anion-exchange resin, Dowex 1x4 in chloride form. During the elution the concentration of potassium chloride in the eluent was increased exponentially. The phosphorus contents in effluent fractions were determined colorimetrically with a molybdenum(V)-molybdenum(VI) reagent (4J. 

In a more recent work Ito [101] has described a simple and highly sensitive ion chromatographic method with ultraviolet detection for determining iodide in seawater. A high-capacity anion exchange resin with polystyrene-divinylbenzene matrix was used for both preconcentration and separation of iodide. Iodide in artificial seawater (salinity, 35 % ) was trapped quantitatively (98.8 0.6%) without peak broadening on a preconcentrator column and was separated with 0.35M sodium perchlorate+ 0.10M phosphate buffer (pH 6.1). On the other hand, the major anions in seawater, chloride and sulphate ions, were partially trapped (5-20%) and did not interfere in the determination of iodide. The detection limit for iodide was 0.2pg L 1 for 6mL of artificial seawater. This method was apphed to determination of iodide (ND-18.3pg L ) and total inorganic iodine (I +I03 -I, 50.0-52.7pg L 1) in seawater samples taken near Japan. 

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