METHOD FOR DETERMINATION OF THE CHROMATOGRAPHIC SURFACE AREA OF REVERSED-PHASE SURFACES

摘要

A method for determination of the chromatographically accessible area of a reversed-phase column is developed. The electrostatically modified linear adsorption isotherm, in combination with the ablution of the linearized Poisson-Boltzmann equation, forms the theoretical basis of the developed method. The column's surface area is calculated by applying this theory to measured adsorption isotherms of charged amphiphiles. The consistency of the method is tested for different negatively charged amphiphiles using mobile phases of different ionic strengths, pH values and different methanol content. It is found that the chromatographically accessible column area is unchanged for-different amphiphilic solutes and when buffer solutions of different compositions are used as the mobile phase (222-230 m(2)/g). The surface area increases to approximately 250 m(2)/g when the mobile phase contains 5 or 10% methanol. The developed method can be used by column manufacturers and by the practising chromatographer to characterize reversed-phase columns, The method is also of theoretical interest since it can be used to calculate the column's phase ratio, which is needed to obtain adsorption entropies.