Terbium-sensitized luminescence optosensor for the determination of norfloxacin in biological fluids

The use of a flow through solid phase terbium-sensitized luminescence system is described for the determination of the widely used fluoroquinolone norfloxacin. A chelate between the terbium ion and the analyte is formed online previously to the sample injection into the carrier stream. Then the chelate is transported towards the flow-through cell, where it is retained on a cationic Sephadex resin packed in the cell, developing the corresponding luminescence signal. Afterwards, an ethylenediaminetetraacetic acid solution was used as eluting agent, in order to regenerate the sensing zone. The system has been satisfactorily applied to the determination of norfloxacin in human urine and serum, without the need of a pre-treatment. The response was linear in the range 10-150 ng ml−1. The detection and quantification limits were 1.5 and 5 ng ml−1, respectively and the R.S.D. 1.82%.