A method of separating an analyte from a biological sample is described. The method comprises providing particles capable of binding said analyte when present in a solution in a container, said container comprising walls, wherein at least a part of said walls is flexible. The particles are suspended in the solution by exerting a force on the flexible part of the walls of the container more than one time. An aliquot of the suspended particles is then removed from the container. The removed aliquot is dispensed into a sample, and the sample is incubated under conditions suitable to immobilize said analyte on the particles. The particles with the bound analyte are then separated from other material and at least part of the biological sample is removed.