A Multi-Technique Forensic Experiment for a Nonscience-Major Chemistry Course

Abstract

This multi-technique experiment with a forensic theme was developed for a nonscience-major chemistry course. The students are provided with solid samples and informed that the samples are either cocaine or a combination of drugs designed to mimic the stimulant and anesthetic qualities of cocaine such as caffeine and lidocaine. The students carry out, in order, color tests, thin-layer chromatographic analysis (TLC), and gas chromatographic–mass spectrometric analysis (GC–MS). The testing methods progress in the sophistication and reliability of their outcomes. In accord with the forensic theme, the color tests and TLC represent presumptive identification methods and the GC–MS an evidentiary method. Presumptive methods are quick and relatively inexpensive but do not provide definitive compound identification. Evidentiary methods identify specific individual compounds. The presumptive identification with TLC is accomplished by comparison of the experimentally determined retardation values with literature values for cocaine and known cocaine mimics. The evidentiary identification with GC–MS is carried out through a visual comparison of experimental and reference spectra.