Investigation of micellar enhancement in simultaneous assay of rosuvastatin and amlodipine in their fixed-dose combined tablets

[Display omitted] •The developed method measured the first derivative synchronous amplitude for rosuvastatin at the zero crossing point of amlodipine and vice versa.•It was found that addition of Tween-80 in a concentration above its critical micelle concentration causes significant increase in the sensitivity.•All the validation criteria were assessed according to ICH guidelines. The native fluorescence of both rosuvastatin and amlodipine was investigated to carry out a new facile method for their simultaneous determination based on synchronous fluorimetric technique. It was found that addition of Tween-80 in a concentration above its critical micelle concentration causes significant increase in the sensitivity of the measurements for the two studied drugs. The developed method measured the first derivative synchronous amplitude (1D) for rosuvastatin at the zero-crossing point of amlodipine and vice versa over the linear ranges of (1.0–10.0 µg/mL) and (0.2–5.0 µg/mL) for rosuvastatin and amlodipine, respectively. All the validation criteria were assessed according to ICH guidelines. The method was further continued to the determination of the two drugs in pure forms, synthetic mixtures, single and combined Tablets with good percentage recoveries that ranged from about (98.0–102.0%). A comparison between the results of the suggested spectrofluorimetric method and previous reports for determination of each of the studied analytes has been carried out and statistical analysis revealed good agreement.