Box-Behnken supported validation of stability-indicating high performance thin-layer chromatography (HPTLC) method: An application in degradation kinetic profiling of ropinirole

Stability-indicating high-performance thin-layer chromatographic (HPTLC) method for the analysis of ropinirole HCl was developed and validated as per the ICH guidelines. The method employed the mobile phase and toluene-ethyl acetate-6 M ammonia solution (5:6:0.5, v/v/v) was optimized with the help of a design expert. Densitometric analysis of ropinirole HCl was carried out in the absorbance mode at 250 and 254 nm. Compact spots for ropinirole HCl were found at Rf value of 0.58 ± 0.02. The linear regression analysis data for the calibration plots showed R2 = 0.9989 ± 0.0053 with a concentration range of 100–3000 ng spot−1. The method was validated for precision, accuracy, ruggedness, robustness, specificity, recovery, limit of detection (LOD) and limit of quantitation (LOQ). The LOD and LOQ were 12.95 and 39.25 ng spot−1 respectively. Drug was subjected to acidic, alkaline, oxidative, dry heat, wet heat and photo degradation stress. All the peaks of degradation products were well resolved from the standard drug peak with significant difference of Rf. The acidic and alkaline stress degradation kinetics of ropinirole, were found to be in first order, showing high stability (t1/2, 146.37 h−1; t0.9, 39.11 h−1) in the acidic medium and low stability (t1/2, 97.67 h−1; t0.9, 14.87 h−1) in the alkaline environment.