Abstract: The development of miniaturized chromatographic systems localized within individual polymer microspheres and their incorporation into a bead-based cross-reactive sensor array platform is described herein. The integrated chromatographic and detection concept is based on the creation of distinct functional layers within the microspheres. In this first example of the new methodology, complexing ligands have been selectively immobilized to create “separation” layers harboring an affinity for various analytes. Information concerning the identities and concentrations of analytes may be drawn from the temporal properties of the beads' optical responses. Varying the nature of the ligand in the separation shell yields a collection of cross-reactive sensing elements well suited for use in array-based micro-total-analysis systems.