Reversed-phase ultra-performance liquid chromatographic method development and validation for determination of impurities related to torsemide tablets.

A simple RP-ultra-performance LC method was developed and validated for determination of impurities related to torsemide tablets. The rapid method provided adequate separation of all known related impurities and degradation products. Separation was achieved on a Zorbax SB-C18 column (50 x 4.6 mm id, 1.8 microm particle size) with binary gradient elution, and detection was performed at 288 nm. The drug product was subjected to oxidative, hydrolytic, photolytic, and thermal stress conditions to prove the specificity of the proposed method. The linearity and recovery were investigated for known impurities in the range of 0.025 to 1.0%, with respect to the drug concentration in the prepared sample. The linearity of the calibration curve for each of the impurities and torsemide was found to be very good (r2 > 0.999). Relative response factors for each of the known impurities were established by the slope ratio method from the linearity study.