Intra-particle sorption rate and liquid chromatographic bandbroadening in porous polymer packings .1. Methodology and validation of the model

An approach is proposed by which an experimentally measured sorption-rate curve for a solute on a chromatographic sorbent may be used to accurately predict the plate height and peak shape contributions of intra-particle sorption rate to the chromatographic peak that will be obtained 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 traditionally identified by the H-s and H-SM plate-height terms. The elution chromatographic column is imagined to be composed of three ''hypothetical columns'' in series, and the hypothetical peak eluting from each is calculated from well-known equations. Numerical convolution of these hypothetical 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 measured on a long column of very large diameter (0.36 mm) porous polymer sorbent. On this column, chromatographic bandbroadening is due nearly exclusively to slow intra-particle processes. The proposed approach is not limited, either theoretically or in practice, to large particles or to porous polymers.