Fairfield Now - Fall 2007
Real world chemistry
By Nina M. Riccio
A two-semester series of courses in chemical instrumentation may not be on everyone's hit list of hot classes. But by the time final projects came around this spring and the alluring scents of coffee and beer wafted through the Bannow Science Center labs, interest in Dr. Amanda Harper-Leatherman's chemical instrumentation courses was definitely piqued.
The upper-level chemistry classes were designed for junior and senior majors with a focus on learning how to use the various instruments in the labs that determine chemical composition and detect chemical interactions. By the end of the spring semester, the students could tell anyone who might want to know about the iron content in spinach, the fat in oil and chips, the main ingredients in pain relief elixirs, and just what it is that makes nail polish remover work so well and smell so bad.
For their year-end capstone project, parameters were fairly straightforward: work in groups of three or four, come up with an analytical problem, and solve it using the instruments in the lab. "To ensure that their ideas were well thought-out, the students first wrote research proposals that included the procedures they intended to use, a timeline, and a hypothesis of what they expected to find," says Dr. Harper-Leatherman.
|And out it comes! As Dr. Amanda Harper-Leatherman (second from left) looks on, Marc Hansel '08, Caitlin Quinn '07, and Jess Fullagar '08 begin bottling their brew.|
"We wanted to do something interesting because we were spending so many hours out of class on these assignments," explains Jess Fullagar '08. "Interesting" for this group was brewing beer - 15 gallons of wheat, amber, and porter - then putting carefully measured samples of each through a high field FT nuclear magnetic resonance spectroscopy (NMR) instrument to detect hydrogen atoms and determine the type and amount of carbohydrate and alcohol in each. A gas chromatography instrument helped determine each brew's diacetyl component (that unwelcome and unavoidable byproduct of fermentation that gives beer its "skunky" taste). The team took hydrometer readings to be sure that density remained consistent and that fermentation was complete. They then compared their three types of homebrewed varieties, using a graph to plot the way they measured up against store-bought brands.
|Using a gas chromatography mass spectrometry instrument, Kristen Zeitler '07 (left), Samantha Seidor '07, Lorraine Lampe '08, and Christopher Koenigsmann '08 extract caffeine from sample cups of coffee.|
Down the hall, the ultraviolet visible spectroscopy instrument was getting a workout. The task set forth by this team: to measure the amount of caffeine and determine what other chemicals they could identify in regular and decaffeinated coffee from Starbucks and Dunkin' Donuts. "Not that all those chemicals are bad," explains Christopher Koenigsmann '08. "Trigonelline helps prevent cavities, quinic acid is an anti-carcinogen, and pyrazine is an antitumor agent." To find those chemicals, they used a process called solid phase micro-extraction. "Instead of using a syringe to extract the liquid they wanted to measure, they used a fiber that adsorbs the components of a solution but not the liquid itself," says Dr. Harper-Leatherman.
The group put the fiber into a gas chromatography mass spectrometry instrument to desorb he components from the fiber, separate them, and detect each of them based on mass. "Once we'd done that, we used a computer-based library to match the signals we obtain with those of known compounds to figure out what each one was," says Koenigsmann. Findings were interesting: the variations in chemical levels between Dunkin' Donuts coffees from two different store locations were minor, while there were greater variations between coffees bought at two different Starbucks. "The students did some sleuthing and found that all Dunkin' Donuts' owners buy from the same supplier, whereas Starbucks owners may buy from different vendors. The fact that Starbucks sells a variety of coffee roasts as compared to Dunkin' Donuts probably makes a difference as well," says Dr. Harper-Leatherman.
|Kathleen Sullivan '08, Michael Shinall '07, and Andrea Della Pelle '08 analyze the metal residue left on a police officer's hand, using the Chemistry Department's flame atomic absorption spectrometer. Dr. Harper-Leatherman looks on.|
Group three began its project at a local firing range. In CSI Miami fashion, this team of chemists was doing a forensic analysis, measuring the residue of antimony, barium, and lead left on the hand after a gun has been fired. "We wanted to know if the amounts found were enough to prove conclusively that a particular person had fired a gun," says Kathleen Sullivan '08. The catch, she explains, is that most of us have trace amounts of these chemicals, particularly lead, on our hands from water or soil; someone who fires a gun would presumably have more, but there is no baseline. Indeed, swabbing the hands of random people on campus showed a great variation in the levels of metallic residue on their skin.
"We set forth to examine two things," says Sullivan. "First, is the change in the concentration of metals enough to prove conclusively that this person shot a gun? Second, is it possible to analyze the amount of residue to determine the number of shots fired?" At the firing range, students swabbed the hands of a police officer to determine how much residue was present after he fired one, two, three, and four shots; afterwards, they used a flame atomic absorption spectrometer to measure how much light is absorbed by each sample. "If there's a lot of any of these metals in a sample, less light is going to pass through because it's absorbed instead of transmitted," explains Sullivan.
Cool to be chemists
"These students had fun and they learned a lot, but make no mistake: These were serious scientific investigations in which they developed procedures, analyzed errors in their data, and gave a rigorous interpretation of results," Department Chair Dr. Matt Kubasik is quick to point out. One reason students are able to do these types of projects, he adds, is the generous support of alumni, foundations, and government agencies including the National Science Foundation. "The NMR, the atomic absorption spectrometer - these are significant instruments, and we could not have purchased them without the donations and grants we've received."
Dr. Kubasik is not one to brag, "but we've been lucky in this department in that we attract some of Fairfield's best students," he says. "They're solid and talented, and they often go to medical or grad school, and continue on in the field. We'd like to keep attracting these kinds of students, and I think projects like these help set a standard for real-world relevance."