ABSTRACT. Saxitoxin and gonyautoxin 2 and 3 are among the most toxic components of the Paralytic Shellfish Poison from red tides. Being small molecules, they often require to be immobilized in order to be handled experimentally. Here is presented a methodology for covalently binding the toxins to carboxilate-modified surfaces. Both toxins were successfully bound to magnetic beads and saxitoxin was additionally bound to a modified golden surface in order to perform a surface plasmon resonance analysis. Success of binding to magnetic beads was evaluated through a standard immune-based toxin assay. Despite the different methods used for each toxin, the maximum binding yield for both toxins occurred when using concentration of 120 µM.