Validation of an HPLC-UV method for the determination of digoxin residues on the surface of manufacturing equipment

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 methods to determine trace amounts of drugs have, therefore, to be considered with special attention. An HPLC-UV method for the determination of digoxin residues on stainless steel surfaces was developed and validated in order to control a cleaning procedure. Cotton swabs, moistened with methanol were used to remove any residues of drugs from stainless steel surfaces, and give recoveries of 85.9, 85.2 and 78.7 % for three concentration levels. The precision of the results, reported as the relative standard deviation (RSD), were below 6.3 %. The method was validated over a concentration range of 0.05-12.5 µg mL-1. Low quantities of drug residues were determined by HPLC-UV using a Symmetry C18 column (150×4.6) mm, 5 µm) at 20 °C with an acetonitrile-water (28:72, v/v) mobile phase at a flow rate of 1.1 mL min-1, an injection volume of 100 µL and were detected at 220 nm. A simple, selective and sensitive HPLC-UV assay for the determination of digoxin residues on stainless steel was developed, validated and applied.