MODIFIED LIQUID-CHROMATOGRAPHY AND FLOW M ICROCALORIMETRY FOR DETERMINATION OF SURFACTANT ADSORPTION

Modifying a liquid chromatography equipment, a novel measuring techniq ue was developed for determination of adsorption isotherms of surfacta nts from solution. This system, combined with a flow microcalorimeter, permitted simultaneous measurement of heat of displacement and adsorp tion data. Using only one gradient pump for moving the liquid phase, t he whole set-up can be made fully automatic. Our aim was to introduce this apparatus through the measurement of adsorption of a cationic sur factant from water. Adsorption isotherms and enthalpy of displacement isotherms of dodecylpyridinium chloride on porous glass were determine d at 45 degrees C and three various electrolyte concentrations. The ad sorption of surfactant molecules is exothermic, the calculated molar e nthalpy of adsorption is larger by a factor of 1.5-2 than the correspo nding heat of micellization.