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

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.