Amberlite CG 120 resin

Biguanide is absorbed by cation exchange resins and is eluted therefrom with hydrochloric acid. 1,1-Dimethylbiguanide, absorbed on Amberlite CG-120 resin, may be eluted (508) with solutions of sodium and potassium dihydrogen phosphate. 

PREPARATION OF CATION-EXCHANGE RESIN. Amberlite CG-120-H cation-exchange resin is placed in a 600 cm3 beaker about 3 g of dry resin (10-meq capacity) is required for each 0.9 x 15 cm column. The resin is covered with 3N NH4OH, swirled for 30-60 min, and allowed to settle. The NH OH is decanted off, and the process is repeated twice. The resin is then washed with doubly distilled water until it is approximately neutral. 

Trifluoroacetates have been applied to the analysis of sugars in the same way as acetates. Imanari et al. [445] analysed aldoses after a prior reduction, as follows. A 0.5-ml volume of 1% NaBH4 in water was added to 0.5 ml of an aqueous solution containing 100-500 pg of a mixture of aldoses. The solution was allowed to stand at room temperature for 30 min and the excess of borohydride was decomposed by adding 0.5 ml of Amberlite CG-120 (H+). The resin was removed by filtration and the filtrate was evaporated to dryness. Borate was removed by the three-fold addition of 1 ml of methanol and subsequent evaporation. The residue was vacuum dried and dissolved in 0.1 ml of ethyl acetate and 0.1 ml of TFA anhydride. After 30 min at room temperature, 1—2 pi were taken for analysis. The resulting derivatives were more volatile than acetates and provided symmetric peaks on a column packed with 2% of XE-1105 (see Fig. 5.30). 

The wash water of the above CG-50 column was adjusted to pH 7.0 and applied on a column of Amberlite IR-120 (H+ form, 30 ml). The column was washed with water and then eluted with 1 N ammonium hydroxide. Ninhydrin-positive fractions were combined, treated with active carbon and neutralized with IRC-50 resin (H+ form). The solution was concentrated to a small volume, treated with ethanol, and kept in the cold overnight to yield 160 mg (75%) of amino-a-hydroxybutyric acid as colorless needles which melted at 217°C-218°C. [a]D23= -30.3° (c=1.0%, H20). 

Amberlite resin CG-120 (H) Type 1 100-200 mesh [Fluka Chemical] may also be used with 0.60 M HCl as eluent. 

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