The present invention provides methods for detecting the presence of an analyte indicative of various medical conditions, including halitosis, periodontal disease and other diseases are also disclosed. The composition includes a peroxide, a water-soluble aminopolycarboxylate chelating agent, and an amount of a buffering agent sufficient to adjust a pH of a mass of the contaminant to between 7. Based on results of the first scan, a plurality of risk values, which correspond to particular types of contraband, are generated.