A cation-exchange column packed with CM-Sephadex C25 matrix was evaluated for its efficiency, capacity, elution volume, and reproducibility in purifying crude extracts of rapeseed or meal for the determination of sinapine content. Combined with a single extraction and ion-exchange column purification procedure, sinapine content in the seed or meal could be quantified with a coefficient of variance of 3.9%. Recovery of sinapine from rapeseed or meal using this method was 95-114% with a lower limit of the sinapine detection of 2.5 µg/mL. The proposed method is not labor-intensive and is applicable to batch analysis of up to 120 samples per day, thereby reducing the cost of analysis.