Development and validation of a spectrofluorimetric method for the analysis of tolfenamic acid in pure and tablet dosage form.

Tolfenamic acid (TA) is commonly used in humans and animals because of its anti-inflammatory, antipyretic, and analgesic effects. So far, no study has been carried out to develop a validated spectrofluorimetric method for determination of TA. Therefore, the present study aimed to develop and validate a simple, accurate, rapid, economical, and precise spectrofluorimetric method to assay TA in its pure and dosage forms, and also in degraded solutions. The fluorimetric method had higher sensitivity compared with the spectrophotometric and high-performance liquid chromatography methods and could determine the drug at the microgram level. Optimum pH of TA for maximum fluorescence intensity was 3, and its two pK(a) values were calculated as 1.95 and 4.05. The proposed method was validated according to the guidelines of the International Council for Harmonisation, and parameters such as linearity, range, accuracy, precision, sensitivity, robustness, specificity, and solution stability were tested. Stress-induced degradation studies on TA did not affect the accuracy and precision of the proposed method. The results obtained indicated that the method was linear over the concentration range 0.2-0.9 x 10(-3) M with good accuracy, precision, and robustness for assay of TA in its pure and its tablet dosage forms and was comparable statistically with the British Pharmacopoeia method.