Chemical analyses

A method of separating compounds of relatively low molecular weight substantially not greater than about one kilodalton from compounds having relatively high molecular weights substantially an order of magnitude greater or more than said low molecular weight compounds in a liquid mixture of said compounds, said method comprising the steps of

• flowing said mixture through a chromatographic body formed of a substantially uniformly distributed multiplicity of rigid, solid, porous particles having chromatographically active, hydrophobic exterior and pore surfaces, average diameters of not less than about 30 .mu.m, and average pore diameters sufficiently small to substantially exclude introduction of said compounds of relatively high molecular weight into said pores, the flow of said mixture being at a velocity sufficient that within at least a substantial portion of the interstitial volume between said particles said flow is at a reduced velocity greater than about 5,000, so that said high molecular weight compounds are swept through said body without substantially binding chromatographically within said pores and exit from said body in a relatively tight band;
• after said band of high molecular weight compounds has exited said body, eluting said relatively low molecular weight compounds from said body with an eluant liquid at a reduced velocity less than 5000;
• and
• thereafter recovering at the exit of said body the eluted relatively low molecular weight compounds separately from said relatively high molecular weight compounds.