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

A method for determination of the chromatographically accessible area of a reversed-phase column is developed. The electrostatically modifie d 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 apply ing this theory to measured adsorption isotherms of charged amphiphile s. The consistency of the method is tested for different negatively ch arged amphiphiles using mobile phases of different ionic strengths, pH values and different methanol content. It is found that the chromatog raphically accessible column area is unchanged for-different amphiphil ic solutes and when buffer solutions of different compositions are use d 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% metha nol. The developed method can be used by column manufacturers and by t he practising chromatographer to characterize reversed-phase columns, The method is also of theoretical interest since it can be used to cal culate the column's phase ratio, which is needed to obtain adsorption entropies.