Separation of caffeine, acetanilide, phenacetin, and acetylsalicylic acid by an ion-exchange chromatography: Application of ion-exchange resins to medicinal analysis. XVII

The separation of caffeine, acetanilide, phenacetin, and acetylsalicylic acid by taking advantage of the difference of affinity to strongly basic resins AG-I, X 8 (100200mesh) in acetate form, has been investigated. The capacity of adsorption by a batch method is increased as follows; caffeine, acetanilide, phenacetin, acetylsalicylic acid. Caffeine is not adsorbed at all, acetanilide and phenacetin are a little, acetylsalicylic acid is much adsorbed. Acetanilide and phenacetin were not separated by means of ethanol (520v/v%) and dilute acetic acid (0.21N) or their mixture in the column operation. The separation of acetanilide and phenacetin was possible by using water as eluate, and column of 35cm (inside diameter 9mm), but phenacetin was eluted by using mixed solution of ethanol and dilute acetic acid (0.2N) in order to avoid tailing. The aqueous solution of acetylsalicylic acid is slowly hydrolyzed, and it gives salicylic acid and acetic acid. The acetylsalicylic acid was eluted with 6N acetic acid as eluate, but salicylic acid was not eluted, this was applied to its separation. The mixed sample (each 12mg) was adsorbed on the column (9×350mm) at the flow rate is 0.5ml/min. The water as eluate was passed through on the column for eluting caffeine and successively, acetanilide. The mixed solution of ethanol and 0.2N acetic acid (2:8) was then applied for eluting phenacetin, in the last, acetylsalicylic acid was eluted with 6N acetic acid. The components in effluent after each fraction (10ml) in a single volume were determined by u.v. spectro-photometry, that is, the absorbance of caffeine was measured at wavelength 270nm, acetanilide at 235nm, phenacetin at 245nm, and acetylsalicylic acid at 275nm respectively against reagent blank and the determination was made by using their calibration curves. The recovery of each component was 99105% in means (n=8) and coefficient of variation was ranged from 2 to 7%. The separation and determination of aspirin(acetylsalicylic acid), phenacetin, and caffeine powders of J.P. (VIII) were performed by this method, and good results have been obtained.