Development of a flow fluoroimmunosensor for determination of theophylline

Abstract

A new fluorescence immunosensor for theophylline with on-line incubation and in situ fluorescence detection was developed to overcome interference problems and speed up sample throughput. Protein A on controlled-pore glass acts as a solid-phase immunoreactor sited in the flow cell of the spectrofluorimeter. The immunosensor has a limit of detection of 0.3 ng ml^–1, a throughput of 10–12 samples per hour and high reproducibility (4.4% at 2.5 ng ml^–1 and 3.3% at 3.75 ng ml^–1) and selectivity. Possible interferents such as 7-(2,3-dihydroxypropyl)theophylline, caffeine and aminophylline do not interfere up to concentrations 50-fold higher than that of the theophylline present. This immunosensor was successfully applied to the determination of theophylline in serum samples.