Development and validation of a liquid chromatographic method for the determination of amlodipine residues on manufacturing equipment surfaces

In the pharmaceutical industry, an important step consists in the removal of possible drug residues from the involved equipments and areas. The cleaning procedures must be validated and the methods to determine trace amounts of drugs have therefore to be considered with special attention. A high performance liquid chromatographic method for the determination of amlodipine residues in swab samples was developed and validated in order to control a cleaning procedure. The swabbing procedure was optimized in order to obtain a suitable recovery of amlodipine from stainless steel. A mean recovery close to 90% was obtained when two swabs moistened with methanol were used. The residual amlodipine was chromatographed at 25 °C in the isocratic mode on a RP-18 stationary phase using a mobile phase consisting of acetonitrile, methanol and pH 3.0 triethylamine solution (15:35:50 v/v/v). UV detection was performed at 237 nm. The method was shown to be selective and linear into the concentration range varying from 0.39 to 1.56 μg/ml. Accuracy and precision of the method were also studied. The limits of detection and quantitation were evaluated to be 0.02 and 0.08 μg/ml, respectively. The stability of amlodipine at different steps of the sampling procedure and the precision of the swabbing procedure were also investigated.