An update of approaches toward the fluorescence immunoassay of drugs

Non-isotopic immunoassays have been developed for many of the analytes of interest in the clinical and toxicologic laboratories. A short review of potential developments and applications of fluorescence immunoassay (FIA) techniques is presented. Although many forms of FIA have been reported, they may all be categorized as either homogeneous (non-separation of phases) or heterogeneous (separation of phases) in nature. The basis of this categorization and its usefulness in drug analyses have been evaluated. A method using a substrate-labeled theophylline derivative is described as an example of an end-point homogeneous FIA system, while a technique utilizing a second antibody precipitation for the analysis of gentamicin is used as an example of a heterogeneous FIA technique. A comparison of relevant analytical parameters has revealed that homogeneous and heterogeneous FIA techniques offer some advantages over other immunoassay techniques.