title: Direct homogeneous phosphoroimmunoassay for carbamazepine in serum.
abstract: In this "phosphoroimmunoassay," a phosphorescent label is used: erythrosin (tetraiodofluorescein). Its long-lived phosphorescence was detected after pulsed excitation in a time-resolved luminescence spectrometer. To achieve convenient open-atmosphere phosphorimetry in liquid solution at room temperature, we used sodium sulfite as an "in situ" chemical deoxygenator, to eliminate oxygen quenching of the excited triplet state. Time-resolved detection allows for complete rejection of short-lived background signals, including those from fluorescent or light-scattering components of biological fluids that can interfere in fluoroimmunoassays. We chose the antiepileptic drug carbamazepine (CBZ) and its active metabolite CBZ-10, 11-epoxide (CBZE) to demonstrate the development and validation of nonseparation assays based on quenching the phosphorescence of erythrosin-labeled drug upon binding to antibody. These two compounds cross reacted equally with the antiserum used; hence, we measured the activity of both in patients' sera. Alternatively, simple pre-treatment of the sample with acid destroys CBZE immunoreactivity and enables specific assay of CBZ.
mesh_terms: D002220:Carbamazepine / Q000031:analogs & derivatives / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D004923:Erythrosine; D006801:Humans; D007118:Immunoassay / Q000379:methods; D008163:Luminescent Measurements; D013696:Temperature
chemical_list: D002220:Carbamazepine; D004923:Erythrosine; C012227:carbamazepine epoxide