Methods and systems for processing samples fixed to a porous substrate generally comprising, a compressor defining one or more fluid isolation areas, a support, for the porous substrate, having an opening corresponding to one or more of the fluid isolation areas of the compressor, an actuator that causes at least a portion of the compressor to press against the porous substrate, a fluid inlet having access to the fluid isolation area at least when the compressor is pressed against the porous substrate, and a fluid outlet to receive fluid, through the opening in the support corresponding to the fluid isolation area of the compressor, at least when the compressor is pressed against the porous substrate.