Methods and apparatus for separating, concentrating and/or detecting particles are disclosed. The particles are enriched within a separation medium by binding to an immobilized affinity agent. Contaminants and/or undesired particles are washed off the separation medium. The affinity agent is mobilized or the interaction between the particles and the immobilized affinity agent is disrupted. SCODA fields are applied within the medium to separate, concentrate and/or detect a target particle.