Microscale chemistry, which began a decade ago as an effort to save money on a major lab renovation at a small New England college, today has revolutionized undergraduate chemistry. This system, which uses techniques and equipment that allow students to work economically and safely with relatively minute amounts of chemicals, is now implemented in colleges throughout the United States and is the subject of several textbooks and lab manuals.
It all began in 1980, when renovation of the antiquated ventilation system in the organic chemistry labs at Bowdoin College, Brunswick, Maine, could be put off no longer. Funds for the improvements were scarce, however, so instead of spending $250,000 to install a whole new system of fume hoods and vents, Bowdoin's chemistry professors developed an entirely new way of doing undergraduate chemistry. The techniques and equipment they designed, in collaboration with professors from Merrimack College in North Andover, Mass., enable students to obtain reactions with amounts as small as 50 to 150 mg of reagent. Typical "macroscale," or standard, experiments generally require amounts of at least 5 to 15 grams. Such a vast reduction in chemicals succeeds in substantially cutting down on the amount of fumes produced in organic labs, among other advantages.
| Although Bowdoin College's Dana Mayo and Samuel Butcher and Merrimack College's Ronald Pike are generally credited with starting the microscale movement, others have contributed different approaches to reducing the amount of chemicals used in the undergraduate lab. Kenneth Williamson of Mount Holyoke College in South Hadley, Mass., for example, has designed equipment somewhat different from Mayo's, and Cornell University's Charles Wilcox has developed scaled-down experiments that, while requiring more material than the amount involved in microscale, use standard glassware and, hence, are more affordable for colleges wishing to scale down. |
At first, Mayo and colleagues tried using small-scale glassware designed for research, but found it awkward. So the Bowdoin and Merrimack professors designed their own glassware specifically for teaching microscale organic chemistry. By 1984, they had arranged with Ace Glass Inc. of Vineland, N.J., to manufacture and market their specialized glassware kits. Today, several glassware companies, including Corning Inc., Corning, N.Y., and Wheaton of Millville, N.J., manufacture similar kits.
Mayo's glassware kits costs about $200 each, depending on the number and size of components included in the kit. The components are basically miniature versions of standard glassware, with ground glass standard taper joints. A typical kit includes an assortment of conical reaction vials ranging in size from .1 ml to 5 ml, a Claisen head, water condensers, and Craig recrystallization tubes. One of the most innovative pieces of equipment available for these kits is the Hickman-Hinkle Spinning Band Distillation Column. This adaptation of a Hickman still, invented in 1984 by Robert Hinkle, then a sophomore at Bowdoin and now a graduate student at the University of Utah, Salt Lake City, uses a spinning band column that attaches from the bottom, and a magnetic stirring plate to make it spin. Previously, bands were spun from a motor at the top of the column, an arrangement too unwieldy for microscale work. Hinkle's adaptation has made distillation, previously one of microscale's weak points, effective on the microscale level.
Williamson used a different approach in designing his glassware. He came up with an inexpensive alternative to Mayo's equipment using polymeric connectors, rather than ground glass, and 100 mm reaction tubes. These reaction tubes, which look like elongated test tubes, have a high surface-to-volume ratio, eliminating the need for the water-cooled condensers used in Mayo's kits. Williamson's kit, distributed by Kontes Life Sciences Products, Vineland, N.J., costs about $100. Williamson acknowledges that his equipment is not appropriate for research, but "for basic educational purposes," he says, "it's fine."
@SIDE R = Both kits have their fans. At the University of California, Los Angeles, chemistry lab coordinator Sandra Lamb started out with Williamson kits, but soon switched to Mayo kits. "It's really much more useful to have the [Mayo] standard taper equipment and have everything fitting together tightly, even for beginning students," says Lamb. "It's closer to the equipment they would use in a standard laboratory." She also likes the Mayo kits because the standard taper connectors allow her to use them with the smaller sizes of conventional glassware. Sally Mallory, who teaches organic chemistry at the University of Pennsylvania, also prefers the Mayo equipment, but points out that the lower cost of Williamson's kits may make it possible for some schools to use microscale that otherwise could not afford it.
According to Robert Minard, a chemistry professor at Pennsylvania State University, a benefit of Williamson's equipment is its efficiency. "You can run a reaction in [Williamson's] 10 x 100 ml test tube," says Minard. "You can recrystallize it in there, you can dry it in there, and you can weigh it in there. If you have to use standard equipment, losses are high in transferring materials." Minard also values the equipment's resiliency--"It's not so fragile," he says. "The flasks bounce on the floor."
A third alternative, and cheaper yet, is to use the smaller sizes of standard glassware. This method, used by Wilcox, a professor of chemistry at Cornell, in Experimental Organic Chemistry; A Small Scale Approach (Macmillan, New York, 1988), scales down standard experiments by a factor of 5 to 10. This approach uses smaller quantities of chemicals and creates less hazardous waste than that produced in standard chemistry, but quantities are not so small that students cannot "see what they're making," says Wilcox. Small-scale chemistry is also more affordable to adopt than microscale, particularly for large schools with sizable inventories of standard glassware. While not as resource-efficient as microscale, this approach is "another movement that's afoot," according to Arden Zipp, chemistry professor at the State University of New York, Cortland. "I suspect that there might be a lot of people who might like to go microscale, but can't afford to right now, so they are downscaling instead." --R.A.
"For years, we've done our students a disservice, because the air quality was so poor at times," says Ronald Pike, chemistry professor at Merrimack. "But we didn't know" that the chemicals they were using were dangerous, he says. "I used to take baths in benzene, almost." Increasing concerns with both environmental issues and occupational hazards led to the search for new methods. Between 1981 and 1984, Pike, along with Bowdoin chemistry professors Dana Mayo and Samuel Butcher, worked on developing special microscale glassware and techniques (see accompanying story). By 1984, they were ready to try their new approach on students.
When the first-ever microscale section of the organic chemistry lab course was instituted at Bowdoin, no undergraduate microscale textbook existed; the students used mimeographed lab notes. In 1986, Mayo, Pike, and Butcher published Microscale Organic Laboratory, (John Wiley & Sons, New York), now in its second edition. That same year, the authors won a Charles A. Dana Award for Pioneering Achievements in Education, in recognition of their leading roles in developing the microscale approach.
As microscale became more widespread, professors who adopted it found that the benefits of the approach were much greater than they had originally realized. In recent years, hazardous waste disposal costs and liability have become perhaps the most pressing reasons schools are converting to microscale. Hazardous waste was the primary reason the University of California, Los Angeles, converted its undergraduate organic chemistry labs to microscale last year. "Waste is just a trickle now compared to what it used to be," says Sandra Lamb, lab coordinator in UCLA's department of chemistry and biochemistry.
SUNY-Cortland's Zipp estimates that at Cortland, the microscale organic lab course with 60 students produces one liter of hazardous waste in one semester. By contrast, he says, a standard organic chemistry lab course may typically produce 1 liter of waste per student during the same period.
Another concern addressed by converting to microscale is toxicity of chemicals used in the lab. Since microscale typically uses a hundredth--or even a thousandth--of the amount of chemicals used in comparable conventional experiments, the degree of exposure to students, as well as dangers from volatile chemical reactions, are greatly reduced. This is important, says James Keeffe, a professor of chemistry at San Francisco State University, "especially for instructors who spend year after year in a lab with maybe 20 amateur chemists with large amounts of chemicals--it's worse on us than it is on them."
Although the initial conversion to microscale can be expensive, depending on the glassware and other equipment chosen, many schools find that the money saved, both in hazardous waste disposal costs and in the costs of renovating inadequate laboratory ventilation systems, is substantial.
In addition, since microscale involves such small amounts of chemicals, professors are expanding the range of materials used to include some that are either too expensive or too dangerous on a larger scale. According to Merrimack chemistry department chairman Zvi Szafran, who is currently working on a textbook for inorganic microscale chemistry, this is especially so in inorganic labs. Without microscale, he says, "you're stuck with chromium and cobalt," relatively inexpensive materials. With microscale techniques, however, "we are able to use a much wider variety of chemicals that had hitherto been impossible, [such as] platinum, palladium, rhodium, which opens up whole new vistas in chemistry." These chemicals cost $60 to $100 per gram, says Szafran. A microscale amount (25 mg) costs $1.50 to $2.50 per student, whereas 10 grams, the amount needed on a macro level, would cost $600 to $1,000 per student.
In addition, says Szafran, substances such as lead, which are so hazardous that it is inadvisable to throw them out even in microscale quantities, can easily be collected and recycled within the microscale lab. Mount Holyoke College's Ken Williamson, a professor of chemistry and author of Macroscale and Microscale Organic Experiments (D.C. Heath, Lexington, Mass., 1989), incorporates this concept into each experiment in his book in a section called "Cleaning Up." This section outlines procedures, to be followed as part of the experiment, for neutralizing or reducing the volume of all the chemicals produced as much as possible. For example, says Williamson, in the oxidation of an alcohol to a ketone, using sodium dichromate as a reagent, a large volume of an aqueous byproduct rich in chromium is produced. Rather than disposing of this aqueous solution, each student can neutralize it to precipitate chromium as the hydroxide, ending up with a small volume of chromium hydroxide powder. This reduces the volume of hazardous waste by a factor of several thousand.
While the economic, environmental, and safety benefits of adopting microscale techniques are substantial, many chemistry teachers are finding unexpected pedagogical dividends as well. According to David Dalton, a chemistry professor at Temple University in Philadelphia, "Students gain confidence in their own abilities to work with small amounts of materials." SUNY-Cortland's Zipp agrees, saying that "students develop better technique with the microscale than they would just doing macro all the time."
Furthermore, reactions occur much faster on a microscale level, allowing students to accomplish much more in the lab. When Szafran was a freshman taking organic chemistry in the 1970s, his class completed four experiments in one semester--"all with the same stuff," he says. By contrast, in the micro-scale inorganic lab Szafran teaches, students do 14 different experiments in a semester, with a much wider variety of materials. Says Mayo, "Students enjoy it because the dullness of taking a lab is reduced, because you're not sitting around waiting for something to happen."
Those who teach micro-scale chemistry agree that one of its greatest advantages is the ethic of conservation it instills in students. "Even when [students] are working with large-scale [techniques]," says Szafran, "they think, `What's the smallest amount we can use here?'" When students move on to jobs in academia or industry, Pike says, they will carry this ethic with them. "All these students now being trained in microscale will push for micro-scale in industry when they get there."
In addition, says Szafran, Third World and Eastern European countries are beginning to express an interest in microscale, faced as they are with severe economic and environmental problems. "I literally [get] mail from all over the country and all over the world," he says.
With all these benefits, one would think that "the microscale revolution" would have completely overtaken undergraduate chemistry by now. However, even its staunchest proponents don't believe students should graduate from chemistry programs with solely microscale experience. "I don't believe for a second that all experiments should be microscale," says Zipp. He points out that some experiments and procedures, such as certain gas law experiments that use mercury to measure pressure, require standard sizes of equipment. In addition, some experiments, such as those involving the neutralization of acids and bases in a general chemistry lab, do not use a lot of expensive materials or produce hazardous wastes, so the savings resulting from using microscale methods would be minimal. Most chemistry professors who have adopted microscale mix it with larger-scale procedures in their chemistry curriculum.
Sally Mallory, senior lecturer in the chemistry department of the University of Pennsylvania in Philadelphia, has developed a scaled-down approach for her basic organic chemistry lab. "What I'm using these days is `semi-micro,' scaled down a lot from five years ago," she says. Typical amounts of materials in her classes' experiments range from .5 to 1 gram, and students use conventional-sized glassware. In her upper-level organic chemistry class, composed of about 25 students, primarily chemistry majors, Mallory teaches microscale.
"I think it's wonderful, but I don't think it's the answer to everything," she says. She points out that it is important for students to learn how to use standard equipment as well as microscale, to prepare them for graduate research or careers in industry. "The students who come out of my two courses know both ways," Mallory says. "They are ready to go out into the world."
She adds that the students at Penn have had no trouble at all adapting to microscale: "My students didn't bat an eye. They were comfortable with it right away."
While Mallory has had success teaching microscale primarily to her upper-level students, Mayo advocates teaching microscale in the basic organic chemistry lab, and teaching scaled-up procedures later on. "It's better to scale up once [students] have learned the precision of microscale," says Mayo, "instead of teaching them sloppy work with large amounts and then trying to teach them microscale."
He stresses that if a school teaches only one organic chemistry class, both micro- and macroscale should be included, so that students gain experience in both techniques. The current editions of both Mayo's and Williamson's textbooks include scaled-up experiments.
Although microscale chemistry in the undergraduate classroom is new, the concept's origins can be traced to Fritz Pregl, an Austrian who won a Nobel Prize in 1923 for developing microanalytical techniques in organic chemistry. In the 1940s, Nicholas D. Cheronis of the University of Chicago tried to introduce microscale chemistry on a graduate research level, but, says Merrimack's Pike, Cheronis's attempt did not come "at the right time at the right place with the right answer." Chemicals were cheap and concern about the environment was low--thus, there was no perceived need for microscale.
Microscale owes its current popularity not only to environmental and economic issues, but also to modern technology. "People didn't make large quantities because they wanted to, but because they had to," says Szafran.
Today, however, advances in instrumentation--infrared spectrometry, gas chromatography, nuclear magnetic resonance spectrometry--allow analysis of very small amounts of material. "We've caught the [undergraduate] lab up with the analytical techniques available today," he adds.
"[Microscale] is a nice juxtaposition of a good idea and the technology catching up to allow its accomplishment." While some maintain that microscale is not "real-life" chemistry, these advances reduce the power of this argument.
The adjustments made in adapting college chemistry experiments to the microscale level are often simple and straightforward. Attaching a spinning band column to a still from the bottom, or devising entire experiments that can be run in a single test tube, generally are not considered earth-shattering developments. Says Robert Minard, a professor of chemistry and director of the organic instruction labs at Pennsylvania State University, "All of these things are kind of trivial, and people smile and say, `so what?'--but they have tremendous impact when you have a lab class of 600 students."
Furthermore, microscale chemistry promotes an ethic of resource conservation that had been lacking in chemistry laboratories until recently. Szafran sums it up this way: "Microscale is not just a process, it's a whole way of thinking about things."