Four simple, low-cost, sensitive, accurate, and direct spectrophotometric methods for risedronate sodium (RIS) estimation have been developed. All methods were based on pyridinyl sensitivity for the UV light at 262 nm. The proposed methods were extensively validated according to the ICH guidelines and proved as following Beer's law over the concentration ranges 6-120, 5-100, 17-170, and 15-150 mu g/mL for methods 1, 2, 3, and 4, respectively. All the proposed methods were found to be precise with RSD values less than 2% and accurate with recovery values between 90-110%. These methods can fully fill the needs of QC routine tests plus meet different demands for Research and Development departments.
