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A single optosensing device based on lanthanide-sensitized luminescence was developed for determination of p-aminobenzoic acid (PABA). The method is based on the formation of a complex between PABA and Tb(III) immobilized on the solid phase (QAE A-25 resin) placed inside the flow cell. NaCl (1 M) was used as carrier solution and HCl (0.05 M) as eluent. The sample solutions of PABA (100 μL) containing Tb(III) and buffered at pH = 6.0 were injected into the carrier stream and the luminescence was measured at λ (ex) = 290 nm and λ (em) = 546 nm. The method shows a linear range from 0.2 to 6.0 μg mL(-1) with an RSD of 1.2% (n = 10) and a sampling frequency of 22 h(-1). A remarkable characteristic of the method is its high selectivity which allows it to be satisfactorily applied to the analysis of PABA in pharmaceutical samples without prior treatment.

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