Fast determination of paracetamol by using a very simple photometric flow-through sensing device

A simple flow-through UV optosensing device was developed for the determination of paracetamol based on its transient retention and concentration on a suitable active solid support (Sephadex QAE A-25 anion-exchange resin) packed in the flow cell and the continuous monitoring of its native absorbance on the solid phase at 264 nm. The sample was injected into a 0.08-M NaCl carrier stream at pH 11.0 by using a simple monochannel FIA manifold. After developing the analytical signal, paracetamol was desorbed from the solid support by the carrier solution itself. A very good linear response was found in the concentration range 0.5-8.0 microg ml(-1) with a RSD (%) of 1.24, a detection limit of 0.022 microg ml(-1) and a sampling rate of 40 h(-1). A strong increase in sensitivity as well as a very much higher selectivity were achieved as compared with the conventional flow injection method as a consequence of the separation of the analyte from the sample plug and its retention on the active solid support placed in the detection area. Applicability of the proposed sensor to direct determination of paracetamol in pharmaceuticals (to solve the sample being the only treatment) was successfully demonstrated.