Device and method for affinity separation

A device for capturing a component present in a fluid, comprising a pipette tip having an open rearward end internally tapered to be a friction fit on a pipette for drawing fluid into the pipette tip, an open forward end, and at least one membrane bonded to and extending across said forward end of the pipette tip, said at least one membrane being a woven or non-woven mesh of fibers and incorporating a specific binding partner of said component to be captured, and said pipette tip being frusto-conical decreasing in internal diameter towards said forward end, wherein the pipette tip is constructed of a brittle plastics material and has between said forward and rearward ends a circumferential line of weakening, provided by an external groove, whereby the pipette tip can be broken manually along said line of weakening.