The use of silver in commercial products has proliferated in recent years owing to its antibacterial properties. Food containers impregnated with micro-sized silver promise long food life, but there is some concern because silver can leach out of the plastic and into the stored food. This laboratory experiment gives students the opportunity to design their own study to measure the leached silver via graphite furnace atomic absorption spectrophotometry. In this experiment, students stored deionized water, tap water, and acetic acid in two styles of silver food containers for a week. The less expensive version of the food container consistently had higher levels of leached silver. The acetic acid samples and microwaved samples also had higher silver levels. Students gained experience with sample design, chemical analysis, and data analysis.

For the past century, humans have been increasingly dependent on plastics, but have not developed adequate disposal practices. In this lab, students are asked whether burning plastic for energy seems like a reasonable disposal technique. To answer the chemical aspects of this question, students use bomb calorimetry to quantify the combustion energy of various plastics. The students confirmed the quality of their data by comparing their results from this experiment with current literature values for various plastic combustions. Their results also show that some plastics contain comparable amounts of energy to that of current fossil fuel and biofuel sources and that the energy content of the plastics vary predictably depending on the presence of oxygen in the polymer structure. At the conclusion of the experiment, students will not only have learned the technique of bomb calorimetry but will have also gained insight into whether burning plastic for energy makes sense from a chemical energy perspective.

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The Water Effects Ratio allows regulators to modify the water quality criteria of metals based on the knowledge that complexing a metal generally reduces its toxicity. Using this logic, the Alameda Corridor Transportation Authority was granted a temporary variance based on bioavailable metal concentration for groundwater discharged into the L.A.-Long Beach Harbor in California. Chelex-labile copper, used as a surrogate for bioavailable copper, was measured using Chelex-100 resin combined with graphite furnace-atomic absorption spectrophotometry (CRC-GFAAS). Ethylendiaminetetraacetic acid (EDTA) was added on-site to a concentration of 10-60 mg L 21 in order to reduce the bioavailable fraction to non-detectable levels, however unexpectedly only ;50% of the available copper was chelated. This partial complexation of the copper was due to high iron concentrations in the industrial mixture of EDTA used for the project, whereas pure EDTA was shown to fully chelate the copper. This technique may hold promise for similar short-term projects. Water Environ. Res., 78, 2508Res., 78, (2006.

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