ABSTRACT The effectiveness of tolfenamic acid and limonin taken together in a single carrier may be useful in pain management. Since no analytical method has been reported for simultaneous estimation of tolfenamic acid and limonin, this study aimed to develop a specific, selective, sensitive, accurate, precise, and eco‐friendly reversed phase‐high performance liquid chromatography method for their concurrent determination in bulk and nanostructured lipid carriers. Separation was achieved on an Agilent 5 µm TC‐C18 column using acetonitrile–water (80:20, v/v) containing 0.1% formic acid under isocratic elution. The developed analytical method was validated following the specifications outlined in the International Conference for Harmonisation Q2 (R1) guidelines. Retention times for tolfenamic acid and limonin were 5.94 and 3.53 min, respectively, at an isosbestic wavelength of 210 nm. Accuracy ranged from 95% to 105%, and relative standard deviation values below 2% for both TOL and LIM indicated excellent precision and consistency. The validated reversed phase‐high performance liquid chromatography method was further applied to determine the %drug entrapment efficiency and %drug loading of tolfenamic acid and limonin in the nanostructured liquid carrier formulation, and to evaluate their in vitro cumulative %drug release profile. In addition, the reversed phase‐high performance liquid chromatography technique's excellent greenness was confirmed by evaluations utilizing the Analytical Eco‐Scale, the National Environmental Methods Index, the Complex Modified Green Analytical Procedure Index, and the Analytical Greenness Metric Approach and Software. The results proved that the RP‐HPLC method was reliable, and it could be used for other lipid‐based nano‐formulations for simultaneous detection in vitro and in vivo, as well as for estimating these two drugs.
Kasana et al. (Wed,) studied this question.