Stability-Indicating HPTLC Method for Quantitative Estimation of Asenapine Maleate in Pharmaceutical Formulations, Equilibrium Solubility, and ex vivo Diffusion Studies

New high-performance thin layer chromatography (HPTLC) has been successfully developed and validated for quantitative estimation of Asenapine maleate in both marketed tablets and in-house developed formulations (solution, microemulsion, nanoemulsion, and mucoadhesive nanoemulsion) as well as for equilibrium solubility study and ex vivo diffusion study of developed formulation through natural membrane. As suggested by the International Conference on Harmonization, different stress test conditions (alkali, acid, thermal, photolytic, and humidity) were used to degrade Asenapine maleate. The samples produced from this study were utilized to develop a stability indicating HPTLC method. The Asenapine maleate was separated well from degradation products using HPTLC plate; precoated with silica gel G 60F(254) on aluminum sheet as a stationary phase and methanol as a mobile phase. Using densitometric analysis, Asenapine maleate was quantified at 235nm. The method produced compact band for the drug (R-f=0.43+0.02). The HPTLC method was validated and statistical analysis of the data confirmed the method to be specific, linear, accurate, precise, reproducible, and selective for Asenapine maleate's analysis. This method was successfully used for assay of Asenapine maleate in both marketed tablets and in-house developed formulations, determining equilibrium solubility in various excipients as well as its ex vivo diffusion study through sheep nasal mucosa from the formulations developed in-house.