HETEROGENEOUS FLUORESCENCE IMMUNOASSAYS USING FLOW-INJECTION ANALYSIS WITH PROTEIN-G SOLID-PHASE REACTORS

Immunoreactors containing immobilized protein G were used in the development of flow injection-based heterogeneous fluorescence immunoassays. Insulin was used as the model analyte and rhodamine isothiocyanate (RITC), whose fluorescence properties are appropriate to the pH changes used in the assays, as the fluorescent label. RITC-insulin conjugate bound to anti-insulin antibodies combined with the protein G column at pH 8.8, and was eluted at pH 2.5. Insulin concentrations of 50 pg ml(-1) could be determined with good repeatability and reproducibility (R.S.D. = 4%), and the protein G reactors lasted for many consecutive immunoassays.