Integrated analytical quality by design-assisted development and validation of an instrumental thin-layer chromatography method for the simultaneous estimation of centchroman and lomefloxacin

The project aims to develop a sensitive, cost-effective, rapid and novel analytical method for the determination of centchroman and lomefloxacin so that in the future it could be used for estimating the drug from different formulations. To develop combination therapy for dysfunctional uterine bleeding (DUB), we selected centchroman, which is a selective oestrogen receptor modulator, and antibiotic lomefloxacin. We further assessed the physical compatibility of centchroman and lomefloxacin and utilized instrumental thin-layer chromatography (TLC) for analytical method development for the simultaneous estimation of both drugs. For developing a sensitive and robust TLC method for the simultaneous detection of centchroman and lomefloxacin, an analytical quality by design (AQbD) approach was employed applying the Box–Behnken design via Design Expert software to optimize the mobile phase for TLC. Physical compatibility was also assessed by analysing data retrieved from Fourier-transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis and forced degradation studies. AQbD analysis suggested a favourable ratio of chloroform–methanol–ammonia–formic acid (8:2:0.1:0.1, V/V) for the efficient separation of both drugs. The retention factors (R_F) were determined as 0.54 for centchroman and 0.26 for lomefloxacin. The method was subsequently validated following the guidelines of the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) Q2 (R1). A linear relationship was established between the concentration range and the peak area, with a correlation coefficient (R²) ≥ 0.999. The detailed compatibility assessment of two drugs also reflected no significant physical or chemical interactions of centchroman and lomefloxacin. Overall, the developed method demonstrated high accuracy, precision and robustness for selected drugs. Moreover, the physiochemical compatibility study conducted showed that both drugs were compatible and did not cause any alteration in the physical or chemical properties of the two drugs.