Abstract: A method for preparing an ultrapure water, from which impurities including inorganic salts, organic substances, fine particles and microorganisms are removed, by treatment including an ion exchange treatment, which comprises using an ion exchange resin comprising a copolymer of a polyvinyl compound and a monovinyl aromatic compound which may contain a monovinyl aliphatic compound, as the matrix, at least in a mixed bed ion exchange treatment of the ion exchange treatment, said ion exchange resin used comprising at least a regenerated form ion exchange resin A eluting an organic compound of a molecular weight of less than 3,000 but substantially not eluting an organic compound of a molecular weight of not less than 3,000 when dipped in a hot water at 50.degree. C. for 7 days.

Abstract: In a method of separating phenylalanine and cinnamic acid from a mixed solution containing phenylalanine and cinnamic acid, a method of separating phenylalanine and cinnamic acid which comprises subjecting said mixed solution to chromatographic development using a synthetic adsorbent, such as Diaion, Amberlite etc., in the presence of a salt, such as ammonium halides, ammonium sulfate, alkali metal nitrates, ammonium and alkali metal salts of fatty acids, at a concentration in the range where the salting-out effect on cinnamic acid is greater than that on phenylalanine and also both phenylalanine and cinnamic acid can be dissolved, for example, in the range of 0.2-5N.