Liquid-liquid extraction and ion-exchange chromatography are efficient methods for sequestration of metal ions, but these methods are poorly suitable for microfluidic miniaturization. Here we examine several methods for rapid extraction, fluorometric detection, and the subsequent isotope analysis of lanthanide ions sequestered on surface modified magnetic microspheres as a versatile platform for chemical manipulation. The assays involve immobilization of a mixed-ligand complex of luminescent lanthanide ions at the surface of polystyrene microspheres. Using the ion-exchange properties of these microspheres, this scheme can be extended to the detection of nonluminescent ions.