Purification of substances from a biological sample

A method for purifying a target substance from a sample comprising the steps of:

• (a) providing a solid phase with an immobilized reactant R1 wherein R1 comprises at least one group that binds specifically to said target and at least one group comprising a first partner of a binding pair, wherein the binding pair is characterized by having an affinity constant from about 106 l/mol to 1010 l/mol, and wherein binding of R1 to said solid phase occurs by means of an immobilized reactant R2 which comprises a group comprising a second partner of said binding pair,
• (b) contacting said sample with said solid phase resulting in adsorption of said target onto said solid phase via binding to R1,
• (c) separating non-adsorbed sample components from said solid phase,
• (d) contacting said solid phase with a first partner of said binding pair or analog thereof in free form resulting in desorption of said target as a complex with R1 from said solid phase, and
• (e) separating said complex from said solid phase.