Simultaneous potentiometric and fluorimetric determination of diclofenac in a sequential injection analysis system Original Research Article

Two independent methods for the determination of diclofenac were simultaneously implemented in an automated analytical system, based on the concept of sequential injection analysis, providing real-time assessment of results quality. The potentiometric detection was carried out with an ion-selective electrode based on a cyclodextrin while for the fluorimetric determination the sample was previously subject to in-line irradiation with UV light. The potentiometric and photochemical-fluorimetric determinations exhibited linear working ranges of 5×10−6 to 1×10−2 and 1×10−6 to 1×10−4 mol dm−3, respectively. Relative standard errors of 0.5% for the potentiometric determination and 0.6% for the photochemical-fluorimetric determination were obtained after 10 consecutive injections of a 5×10−5 mol dm−3 diclofenac standard solution. The sampling rate was about 32 samples h−1. Both methods were applied in the analysis of pharmaceutical formulations. The quality of results obtained was evaluated by comparison to the reference method, with no statistically significant differences for a 95% confidence level.