Flow System with Electrochemical Detection for Determination of Paracetamol in Pharmaceutical Preparations

A FIA system with electrochemical detection was developed for the automatic determination of paracetamol in pharmaceutical formulations. The analytical difficulties caused by adsorption of matrix excipients in the electrode surface were surpassed by an on-line electrochemical regeneration of the glassy carbon tubular electrode, using the carrier solution, enabling the renewal of the electrode surface in a simple and rapid way. A single channel FIA manifold was developed, which provided reproducibility of sample transport to the detector and minimized the contact time between samples and electrode surface, thus reducing its cleaning frequency and permitting a high sampling rate to be achieved. Furthermore, the physical characteristics of the electrochemical cell permitted its easy incorporation in the FIA manifold, offering robustness to the system, and allowed it to be generalized to routine analysis applications. With the optimized parameters, a linear correlation between paracetamol concentration and peak current intensity was obtained up to 4 x 10(-4) mol L-1, with a detection limit of 2.5 x 10(-5) mol L-1. Paracetamol was quantified in pharmaceutical dosage forms and the results were compared to those obtained for the official spectrophotometric method (BP 1998). Correlation between the results obtained by both methods was linear and no statistical difference between methods was found at the 95% confidence level.