SIMULTANEOUS DETERMINATION OF MEFENAMIC AND FLUFENAMIC ACIDS IN REAL SAMPLES BY TERBIUM-SENSITIZED LUMINESCENCE

A simple luminescent methodology for the simultaneous determination of mefenamic and flufenamic acids is proposed. The method takes advantage of the lanthanide-sensitized luminescence, which provides increased sensitivity. Due to the strong overlapping between the luminescence spectra, the use of decay curves to resolve mixtures of the analytes is proposed, particularly as these curves are more selective. A factorial design with three levels per factor coupled to a central composite design was selected to obtain a calibration matrix of thirteen standards plus three blank samples which was processed using a partial least-squares (PLS) analysis. In order to assess the effectiveness of the proposed method, a prediction set of synthetic samples was analyzed, and recovery percentages between 96 and 106% were obtained. Limits of detection, calculated by means of a new criterion, were 3.73 mu g L-1 and 14.61 mu g L-1 for flufenamic and mefenamic acids, respectively. The method was tested in two different pharmaceutical preparations containing the analytes, obtaining recovery percentages close to 100%. Finally, the simultaneous determination of both fenamates in human urine samples was successfully carried out by means of a correction of the aforementioned model. No extraction method or prior separation of the analytes were needed.