In some embodiments, the present invention pertains to a method for detecting an adulterant in a biological sample. A combination of a biological sample, an agent for detecting the adulterant and an ionic moiety capable of undergoing reduction by gaining electrons is provided in an assay medium. The combination is incubated under conditions sufficient for the ionic moiety to undergo reduction and for the agent for detecting the adulterant to interact with the adulterant. The reduction of the ionic moiety enhances the detection of the adulterant as a result of increasing the sensitivity of the agent for detecting the adulterant. The extent of interaction between the agent for detecting the adulterant and the adulterant is measured and is related to the presence or absence of the adulterant in the biological sample.