Single column chromatographic determination of small molecules in mixtures with large molecules

A process for separating molecules of at least two different sizes from a sample containing such comprising the steps of (1) adding a sample that contains at least two different size molecules to a device that contains a porous separation medium having at least two different types of functionalites with each different type of functionality segregated in pores of different sizes, (2) separating the smaller molecules contained in the sample by eluting them with a first mobile phase leaving the larger molecules sorbed in the porous medium, and (3) thereafter eluting the largest of molecules by washing the porous separation medium with a different mobile phase.