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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.

Figure 1. A thermal ellipsoid plot of the structure of (η 6 -p-fluoroaniline)chromium(tricarbonyl).

This general chemistry laboratory uses differences in solubility to separate a mixture of caffeine and aspirin while introducing the instrumental analysis methods of GCMS and FTIR. The drug mixture is separated by partitioning aspirin and caffeine between dichloromethane and aqueous base. TLC and reference standards are used to identify aspirin precipitated by acidifying the aqueous layer and the caffeine is recovered by evaporating the dichloromethane. FTIR analysis of the isolates is intended to provide an introduction to both the basic operation of a FTIR spectrometer and experience in matching library reference spectra to FTIR spectra of unknowns. GCMS analysis parallels the wet chemistry separation and FTIR identification of the components in the drug mixture. Used as a re-introduction to GCMS, emphasis is placed on how GCMS combines sample separation and component analysis into one operation. This laboratory is intended to be part of a suite of vertically integrated laboratory exercises linked by a forensic theme. Proceeding experiments in the suite are centered on the theory and application of TLC for forensic analysis. Subsequent experiments are focused on the use and interpretation of FTIR and GCMS for analysis.