Differential Identification of Six “Mystery” Substances Using Three Distinct Analytical Techniques in a Forensic Science Laboratory

It is widely known that active learning exercises in analytical chemistry that are used to solve real life problems can stimulate student interest. A specific area that stimulates student interest is the application of analytical chemistry in the field of forensic science. Based on the growing interest in forensic science, this laboratory utilizes three analytical techniques to identify six unknown compounds. In the present exercise, students learn to apply presumptive, mid-level, and confirmatory tests to identify six unknown over the counter (OTC) drugs (Aspirin, Aleve, Diphenhydramine, Caffeine, Lidocaine and Pseudoephedrine). These drugs were chosen based on their ease of acquisition and ability to mimic illicit substances when these tests are performed. Two different color spot tests (Cobalt thiocyanate and Marquis) are used for presumptive testing. The OTC drugs are dissolved in a range of solvents for thin layer chromatography (TLC) analysis to narrow down the possible identities of the drugs. Finally, using Nuclear Magnetic Resonance (NMR) to obtain the organic structures of the unknown drugs, students are able to conclusively identify the drugs.