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Several of the Arkansas State University chemistry faculty have elected to make environmental chemistry a focus of the laboratory experience to teach basic principles in instrumentation, physical chemistry, and inorganic chemistry courses. Additionally, in the undergraduate research laboratory required for a BS degree, they have mentored students in environmentally relevant projects. The instrumentation involved in these undergraduate experiences were the Varian Spectra250+ with GTA-97 graphite furnace atomic absorption (GFAA) spectrometer and the Seiko TG/DTA320 Thermal Analyzer.
TGA methods are currently used in physical chemistry and inorganic chemistry as stand-alone experiments to introduce the technique to the students. In the physical chemistry laboratory, students use the TGA curve to explain mass loss and predict final product. Samples in this initial year included CuSO4(5 hydrate), FeSO4(7 hydrate), CaC2O4(2 hydrate), and metal carbonates; the behavior of all these compounds is well documented. See figure. Students in the inorganic chemistry laboratory were required to determine the number of waters of hydration, and explain decomposition including the thermicity of the process.
Currently, an integrated inorganic lab experience is being developed based on the chemistry of selected metal polysulfide complexes (environmentally important as models for hydrodesulfurization catalysts). The TGA/DTA methods will be used to study the decomposition of the polysulfide. The decomposition product will be further characterized by powder X-ray diffraction techniques.
The TGA/DTA has been used in Special Problems in Chemistry--the research experience--to study the thermal stability of an organometallic polymer semi-conductor and to study the vapor transport of chromium oxides in the Cr/O/H2O system.
The GFAA became fully operational as the instrumentation course was beginning in the fall of 1994. The graphite furnace mode was demonstrated to the Instrumentation students while the flame mode was used by students to analyze several natural water samples.
In a module of laboratory exercises for the fall 1995 term, students will be expected to set up furnace mode methods and analyze environmental water samples or simulants for trace metals.
The research projects which involved AA usage included a comparative study of metal species in storm water runoff from both an urban industrial park and a supposedly pristine, forested, municipal park located on the outskirts of the city and a study of metal ions in the soil of an Amerindian burial site as locators for individual interment locations.
Acknowledgment
This project was partially supported by a grant, DUE-9351560, from the National Science Foundation Division of Undergraduate Education Instrumentation and Laboratory Improvement Program.
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