Adsorption of atropine and hyoscine on magnesium trisilicate

Abstract

Abstract The adsorption of atropine and hyoscine by magnesium trisilicate has been studied. At relatively low initial concentrations the adsorption data were shown to fit a Langmuir plot and values for monolayer adsorption were 14·9 and 3·8 mg g−1 for atropine and hyoscine respectively. The extent of adsorption was increased at higher initial concentrations due to multilayer formation. The presence of either sodium citrate or sodium phosphate suppressed the adsorption. Elution of the adsorbed alkaloid was dependent on the pH of medium used and followed the order: 0·05n HCl (pH 1·5) >0·01n HCl (pH 2·1) > water (pH 5·5). Due to the dissolution of magnesium trisilicate, at 37° in 0·05n HCl, neither the rate of acid uptake nor the acid absorption test of the adsorbent were significantly reduced by the adsorption of either alkaloid. In the B.P.C. mixture of magnesium trisilicate and belladonna, almost complete adsorption of hyoscyamine occurred and the elution of the adsorbed alkaloid depended on the level of hydrochloric acid in the elution medium used.