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.

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.

Steady state rotating disk voltammetry provides excellent measurement of permeability for films and layers on electrodes because the hydrodynamic control of rotating disks establishes well defined boundary layers normal to the electrode. For a redox probe present in solution and pre-equilibrated in the layer, voltammetry measures electrolysis current for the probe as the probe transports from solution, through the film, and to the electrode where the probe is electrolyzed. Diagnostic equations relate the steady state, mass transport limited current iss to the rotation rate ω. The incompressible layer is electroinactive about the probe formal potential. Diagnostics are available for a single layer, uniform film (Gough and Leypoldt). Uniform films are homogeneous with no structural features. Here diagnostics are provided for bilayer and multilayer uniform films, where multilayers include discretely and continuously graded films. Consideration of serial mass transport resistances normal to the electrode allows diagnostics for uniform films. Heterogeneous, micro- and nano-structured layers are structured in the plane of the electrode. Consideration of parallel mass transport resistances as part of the layer mass transport resistance yields diagnostics for heterogeneous films. Diagnostics are vetted with literature data. Theoretical and practical advantages and limitations are noted.

In the first-year general chemistry laboratory course, instrumental data collection involving sample quantification has often been limited to absorption spectroscopy due to the inaccessibility of emission techniques suitable for large enrollments and novice users. In this laboratory experiment, students explore the complementary techniques of emission and absorption spectroscopy, in which sample quantification respectively occurs via the measurement of light emitted or absorbed by the sample. Calibration curves are constructed for both techniques. Eschewing atomic absorption spectroscopy (AAS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES), instrumentation not typically available for large general chemistry courses, quantitative data is instead collected using a series of carefully implemented flame tests. Students perform flame tests on alkali, alkaline earth, and transition metal compounds using the emitted light to gain a thorough understanding of emission spectroscopy. In Week 1, students are introduced to emission spectroscopy through the identification of unknown components in air, lamps, and contaminated soil samples. In Week 2, students carry out quantitative emission and absorption characterization of Na and Cu solutions, comparing the two techniques through experimental observations and analyzed results. Calibration curves with high linear regressions (r 2 > 0.992) are prepared and used to determine the concentrations of provided reference samples, with averaged student data resulting in reasonably low percent errors (<12% for Na emission, <11% for Cu emission, and <2% for Cu absorption) when compared to the known concentrations. Students then compare experimental flame emission results to provided ICP data to gain experience with a sensitive, quantitative emission technique.

The role supporting electrolyte plays on the transport of the redox probe tris(bipyridine)ruthenium(II) chloride through the ion exchange polymer Nafion® was examined using cyclic voltammetry, rotating disk voltammetry, and spectroscopic techniques. Variations in both the extraction coefficient (κ) and the diffusion coefficient (D) were observed as the supporting electrolyte was varied. The anion of the supporting electrolyte was not found to influence mass transport, but the cation significantly influenced both extraction and diffusion of the redox probe within the polymer. A series of monovalent (Li+, Na+, K+, Rb+) and divalent (Mg2+, Ca2+, Ba2+, Zn2+) cations were studied, as well as the trivalent cation La3+.