There is an ever increasing demand for fast,sensitive,inexpensive and reliable methods for the determination of submicromolar concentrations of biomarkers of exposure(i.e.substances the presence of which in biological fluids indicates exposure to dangerous compounds(typically metabolites of those compounds),biomarkers of treatment(typically drugs or their metabolites),and biomarkers of illness(compounds the presence of which indicates starting illness(e.g.tumor biomarkers signaling the onset of cancer).