INTRAPARTICLE SORPTION RATE AND LIQUID-CHROMATOGRAPHIC BANDBROADENINGIN POROUS POLYMER PACKINGS .1. METHODOLOGY AND VALIDATION OF THE MODEL

An approach is proposed by which an experimentally measured sorption-r ate curve for a solute on a chromatographic sorbent may be used to acc urately predict the plate height and peak shape contributions of intra -particle sorption rate to the chromatographic peak that will be obtai ned when the solute elutes from a liquid chromatographic column of the sorbent. The sorption-rate curve is measured on a ''shallow bed'' of sorbent (e.g. approximate to 1 mm) under ''infinite solution volume'' conditions and is fit by an empirical tri-exponential equation. Intra- particle rate processes include the bandbroadening phenomena tradition ally identified by the H-s and H-SM plate-height terms. The elution ch romatographic column is imagined to be composed of three ''hypothetica l columns'' in series, and the hypothetical peak eluting from each is calculated from well-known equations. Numerical convolution of these h ypothetical peaks in series yields the overall predicted elution peak contribution from intra-particle rate processes. The accuracy of this model is demonstrated by comparing predicted peaks with eluted peaks m easured on a long column of very large diameter (0.36 mm) porous polym er sorbent. On this column, chromatographic bandbroadening is due near ly exclusively to slow intra-particle processes. The proposed approach is not limited, either theoretically or in practice, to large particl es or to porous polymers.