Introduction What are Waste Minimization and Pollution Prevention? Why are Waste Minimization and Pollution Prevention Important? Purchasing Chemicals Managing Chemical Inventories Dealing with an Existing Inventory of Unwanted Chemicals Conducting Experiments Scaling Down Experiments Substituting Materials »Alternatives to Wet Chemistry« Reusing and Recycling Chemical Resources Segregating Waste Streams In-Laboratory Treatment of Wastes Working with School Administrators, Students, Other Schools, and the Community Getting More Information Appendix A—Waste Minimization Checklist

In addition to substituting safer chemicals and reducing the scale of experimentation, you might also want to consider avoiding certain experiments altogether. While hands-on wet chemistry experience is important to a certain degree, there are good reasons for exploring alternatives such as instrumental analysis, computer simulation, or even videos. One important consideration is that commercial and industrial laboratories are moving away from wet chemistry and towards instrumentation and simulation whenever possible, so it is important for students to gain experiences with these techniques. In addition, of course, these techniques offer a means of minimizing or avoiding some chemical wastes. Instrumentation Sample separation, purification, and other new techniques and equipment have advanced significantly in the last decade. However, many of the new instruments can be expensive, and can require users to be rather sophisticated. By and large, these instruments are more applicable to higher-level university chemistry classes than to introductory chemistry courses. Chapter 8 discussed several instruments related specifically to microscale experimentation. In addition, there are a number of other instruments that can perform important laboratory analyses with reduced chemical input requirements. Some of these instruments include: ion, liquid, and gas chromatographs mass spectrophotometer IR and UV spectrophotometer nuclear magnetic resonance (NMR) atomic absorption instrument X-ray diffraction instrument These highly sensitive instruments can reduce the quantities of analytes required for testing by 10- to 100-fold. For example, NMR analysis requires a 1 mL sample for quantitative analysis. Again, many of these instruments may be beyond your budget, or may be inappropriate for the scale of your classes. However, keep in mind that just like other technologies (e.g., computers), they may become more affordable and easier to use in time. Sample preparation Another area where alternatives to wet chemistry exist is in the preparation of samples for analysis. Most samples require some extraction and/or concentration in preparation for further analysis. Traditional procedures (liquid-liquid or liquid-solid extraction) are time-consuming and waste substantial quantities of solvents. Solid phase microextraction (SPME) and supercritical fluid extraction (SFE) are two recently developed methods that eliminate the need for solvent to separate analytes. (These methods may not be relevant for high school laboratories.) SPME is a solventless sample preparation method for analysis of organic compounds by gas chromatograph (GC). This approach replaces traditional methods such as purge and trap systems or liquid-liquid extraction. Essentially, SPME is a modified syringe holding a phase-coated fused silica fiber that adsorbs organic analytes when placed in the water sample. The analytes are then desorbed from the fiber into a capillary GC column at the heated injection port. The equipment is fairly small and reasonably priced, and the fibers are reusable up to 100 times. SPME is particularly cost effective when you consider the savings in solvent purchase and disposal. SFE uses the unique characteristics of supercritical CO˛ to extract analytes from a sample, fully eliminating solvent use. Because supercritical fluids have lower viscosity and diffuse more rapidly into a sample, it also greatly reduces sample preparation time. The smaller, more recent SFE equipment models may be appropriate for some classroom settings. These models offer microprocessor controls as well as an elimination of moving parts to make maintenance and use easier. A typical extraction takes about 30 minutes at a material cost of about 10 cents. Computer simulation/videos Again, it is important that students gain laboratory experience in using glassware and equipment. However, due to time constraints in lab courses, and the length of typical introductory experiments, computer simulation may allow students to see a wider variety of experimental results, without generating wastes, and in a much shorter time period. At higher level educational institutions, computer simulation may greatly decrease the amount of chemicals (and wastes) required in research and development by allowing researchers or students to tweak and optimize experiments on a computer instead of repeating experiments again and again at a bench-scale or full-scale level. A number of computer software vendors are producing chemical reaction simulation software. In some cases, this software is quite elaborate and complicated, as it is oriented towards commercial and industrial applications. In other cases, the software might be useful in the classroom. A good resource for more information (in addition to your local software store) might be a regional or state university, many of which have already started to implement simulation software. In addition, more and more information is being provided on the Internet. In addition to computer simulations, you might also be able to teach certain experimental principles by using videos—even “home grown” videos.

Return to Title Page

Copyright © 1996 Battelle Seattle Research Center. All rights reserved.