Abstract: A method is provided for detecting a tracer in a preparation by precipitating a coloring agent from a sample of the preparation, especially where the coloring agent otherwise interferes with detection of the tracer. A sample of the preparation may be contacted with an effective amount of a precipitating agent to precipitate the coloring agent in the sample, yielding a sample supernatant having a reduced concentration of coloring agent compared to the preparation. Detection of the tracer in the supernatant may produce a result which may be evaluated to assist in quality validation in a process of manufacturing the preparation or authenticating the preparation.