A validated UPLC method for the determination of process-related impurities in bulk drug.

An UPLC method has been developed and subsequently validated for the determination of Azathioprine and its process-related impurities. Separation was achieved with Acquity UPLC BEH C18, 100 × 2.1 mm, 1.7 μm column and trifluoroacetic acid (0.05% in water) : acetonitrile as eluent in gradient mode. Flow rate was set at 0.35 mL min-1. UV detection was performed at 220 nm. The method has been validated with respect to specificity, accuracy, precision, linearity, robustness, limit of quantification and limit of detection. The accuracy of the method demonstrated at three levels in the range of 50-150% of the specification limit and the recovery of impurities were found to be in the range of 98 to 102%. The detection limits of the process related impurities ranged between 0.16 and 0.24 μg mL-1. The described method is simple, rapid, linear, precise and robust. The method is useful during process development and quality control of bulk manufacturing.