This chapter provides a detailed description of a network of channels that includes a chamber for trapping beads in a microfluidic device. Instructions are included for the packing and use of the bead bed for solid-phase extraction (SPE). The SPE procedure may be used, e.g., as a filter to clean up a dirty sample prior to analysis, or as a means of pre-concentration for a dilute sample. Once the bead bed is in place, it may be used multiple times without sample breakthrough.
