Stability-indicating HPTLC determination of rivastigmine in the bulk drug and in pharmaceutical dosage forms

A simple, selective, precise, and stability-indicating high-performance thin-layer chromatographic method for analysis of rivastigmine in the bulk drug and in a capsule formulation has been established and validated. Chromatographic separation was achieved on aluminum-backed silica gel 60F₂₅₄ HPTLC plates with chloroform-methanol 4:6 (v/v) as mobile phase. Densitometric analysis of rivastigmine was performed in absorbance mode at 210 nm. The method gave a compact spot for rivastigmine (R _F 0.53 ± 0.02) and was shown to enable excellent separation of a degradation product of rivastigmine (R _F 0.32 ± 0.02). The method was validated for accuracy, precision, linearity, recovery, limits of detection and quantitation, and robustness. Good linearity was observed in the concentration range 200-1600 ng per spot; the correlation coefficient was 0.9916 ± 0.008. The limits of detection and quantitation were 30 and 100 ng per spot, respectively. Rivastigmine was subjected to alkaline hydrolysis and high humidity and found to degrade under these conditions. Statistical analysis proved the method was reproducible, specific, and accurate. The method is stability indicating; because it is economical it can be used for routine analysis of the bulk drug and pharmaceutical formulations.