ESTIMATION OF PARAMETERS USED IN REVERSED-PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY BY MOMENT METHOD

초록

Dept. of Chem. Eng., Inha Univ., Inchon 402-751, Korea To simulate chromatographic separation process and to make a rational design of chromatographic systems, parameters for adsorption rate as well as adsorption equilibrium of each component is essential. In this work, parameter estimation was made for the reversed-phase adsorption of perillyl alcohol (POH), potent anti-cancer agent, on octadecylsilyl-silica gel (ODS). The average particle diameter of ODS was about 15 mm and was packed in the column (3.9´300mm). The mobile phase was mixture of methanol and water, in which the volumetric composition of methanol was in the range from 10 to 40 (vol %). The first absolute moment and the second central moment were determined from the chromatographic elution curves by moment analysis. The experiments were carried out by using POH solutions in linear adsorption range. The fluid-to-particle mass transfer coefficient was estimated by the equation of Wilson-Geankoplis. The axial dispersion coefficient and intraparticle diffusivity were determined from the slope and intercept of a plot of H (H= (m’2/m12)(z/2u0)=(Ez/u02)+H0) vs 1/u0 , respectively. Intraparticle diffusivity is related to both pore diffusivity and surface diffusion coefficient. The surface diffusion coefficient was calculated by subtracting the contribution of pore diffusivity to intraparticle diffusivity. The value of pore diffusivity was estimated from the molecular diffusivity in a bulk phase, porosity of an adsorbent, and tortuosity factor of pores. The contributions of each mass-transfer step were axial dispersion (dax ,dax = (Ez/u02)d02 ), fluid-to-particle mass transfer (df, df = (1-e)(R/3kf)(ep+rpK)2 ), and intraparticle diffusion (dd, dd = (1-e)(R2/15De)( ep+rpK)2 ). The contribution of axial dispersion(dax) was found to range from 20 to 30% and that of fluid-to-particle mass transfer(df) and intraparticle diffusion(dd) were the same order of magnitude.