Determination of risperidone in tablets in the presence of its degradation products and placebo-derived constituents.

New chromatographic-densitometric assay was developed for identification and determination of risperidone in pharmaceutical formulations. Thin-layer chromatographic plates (TLC-F254) as a stationary phase and n-butanol-acetic acid-water (12:3:5 v/v/v) as a mobile phase were used for separation. Densitometric measurements were done for all constituents at lambda = 280 nm. A decrease in stability of risperidone was observed in acidic, basic and antioxidant solutions. Degradation of active pharmaceutical ingredient was consistent with first-order kinetics and unrelated to the solution. This assay is specific for risperidone. No interference of tablet origin adjuvants and degradation products were observed. Moreover, high sensitivity, limit of detection (0.22 microg/spot), limit of quantitation (0.67 microg/spot), recovery (98.2-100.82%), broad linear range (0.09 microg/spot to 1.40 microg/spot) and accuracy (1.87% RSD) are characteristic traits of the chromatographic-densitometric assay.