DeltaNews, May 2003


May 2003	www.deltanu.com
Start next semester with new chemistry experiments…and we’ll do the work for you. See Be Prepared, below. Raman Spectroscopy and Education DeltaNu is pleased to introduce DeltaNews, a newsletter devoted to presenting teaching methods involving Raman spectroscopy. This issue is dedicated to the application of Raman spectroscopy to forensic science. Visit our website at www.deltanu.com where you will find a variety of experiments for next year’s curriculum. See the Be Prepared! section of each newsletter for a tried and tested experiment to add to your curriculum. Why Raman spectroscopy? Raman spectroscopy is information rich and is now easy and fast. Until now, infrared spectroscopy has been the most popular vibrational spectroscopy because Raman spectroscopy was difficult, expensive and unsafe for undergraduate laboratories. DeltaNu’s Advantage™ system changes all of that – it is the instrument that now allows you to introduce Raman spectroscopy into every level of your curriculum. What can Raman spectroscopy add to your curriculum? General chemistry: DeltaNu’s Advantage 200A replaces the outdated single channel UV-Vis spectrometer. (See our on-line workshop demonstrating a simple, nontoxic hydrogen peroxide oxidation.) Interested in Green chemistry? Turn your lab into a recycling center. Have your students bring in their own plastic samples and identify them in seconds using Raman spectroscopy. Organic Chemistry: Tired of taking IR spectra? Raman spectra contain similar information but do not require KBr plates, purged instruments and costly maintenance. Inorganic Chemistry: Want to teach your students about symmetry? Use our polarization feature to show your students totally symmetrical modes and how to assign a vibrational spectrum. Physical Chemistry: Teach your students about molecular interactions. Have them find vibrational overtones and explain anharmonicity to them with their own data.	In this issue: Raman Spectroscopy and Education Forensics: Popular Science Software/Hardware Be Prepared! Lab 7: Investigation of a Crime Scene Contact Us
Forensics: Popular Science Publicity surrounding high profile crimes has popularized the science of forensics. Creating undergraduate laboratory experiments around forensic science or mock crime scenes is an excellent way to stimulate student attention, retention, and teach old but important concepts in a new way. Fingerprints All students know that every person can be identified by their fingerprints. However, the idea of spectroscopic fingerprints is not as obvious. This idea is an excellent lead into the principles of characteristic spectral features and "fingerprint" regions. The spectrum of methamphetamine, shown above, provides students with an example of a spectroscopic fingerprint. This spectrum contains spectral features characteristic of monosubstituted benzene (996 cm^-1). This is the "chemical family" that methamphetamine belongs to. Specifically, the isopropyl carbon-carbon stretching at 836 cm^-1 differentiates it from its close relative, amphetamine. Give your students two white powder samples. Have them fingerprint them with Raman to identify which is illicit and which is ordinary powdered sugar. DeltaNu systems require only microliter quantities of samples, there is no need to prepare or dispose of expensive, toxic, or regulated materials. Anatomy of a Bomb Aside from providing chemical fingerprints to solve crimes, spectroscopy is used every day for security. These days very few people are unfamiliar with airport security. Another example of Raman spectroscopy and its special ability to identify materials comes from nature of explosives. We obtained a small sample of trinitrotoluene (TNT) from our local fire department. It takes seconds and a few milligrams of this explosive to teach your students several fundamental principles of Raman spectroscopy. The spectrum of TNT below was acquired in 5 seconds. The feature at 1350 cm^-1 is characteristic of nitroaromatics. Why is the nitro group’s vibration so large in the Raman spectrum? Why do high explosives contain nitro groups? The look and taste of medicine Pharmaceutical industries do a great cover up when they make our medicine. This is easily demonstrated with Raman spectroscopy. Have your students bring in a pill for Raman analysis. You and your students will be amazed at what the spectra will show when they analyze their pills. On the exterior, Raman spectra of most pills will look the same and not very complex. Drugs are coated to look appealing and to cover up the bad taste. TiO₂ is commonly used as the coating and base pigment. TiO₂ is also the base for common house paints! An educational experience really begins when students scrape off the exterior paint and look inside. Visually, the outside often does not look any different from the inside. But the taste is very different and the Raman spectrum will be very different. In this example, we used Ambien™, a popular sleep aid. The first tip off that something is strange in the Raman spectrum of an Ambien™ tablet is that the complex chemical structure of Ambien™ produces what appears to be a simple Raman spectrum. Have some TiO₂ on hand to show your students that they are swallowing house paint along with their medicine. As they scrape down a little further and they get past the coating they should see Raman features due to the drug. We found that Ambien™ (or, most likely, additional additives) possessed a fluorescent background. Challenges of Real World Samples Raman spectroscopy of forensic samples often challenges the students. Many prescription and nonprescription drugs contain fillers that produce a background in the Raman spectrum. Ambien™ provided such a challenge! The chemical structure of Ambien™ (easily found on the www) is not simple. Its spectrum contains many peaks. To obtain a quality Raman spectrum requires some effort and is guaranteed to keep the industrious student occupied for a while learning firsthand about the relationship between integration, signal averaging, and baseline correction. Our Advantage 200A has a unique real-time baseline feature that automatically subtracts the spectrums own baseline. This is the best approach to challenging samples. Once a good spectrum is acquired and saved, it can be further refined in a spectral data manipulation program such as Grams (www.galactic.com/) or ACD (www.acdlabs.com). The DeltaNu software also allows the user to zoom into specific regions of the spectrum. For our analysis of Ambien™, once we scraped off the TiO₂ coating, we were most interested in the spectral region between 800 and 1650 cm^-1. This region contained over 10 features than could be used to "fingerprint" the tablet. Ask your students why it is best to integrate longer, why it is important to signal average if your sample has a high background, and how the DeltaNu system can remove most baseline features automatically.
Software/Hardware In the past, Raman spectroscopy was an esoteric spectroscopic method performed in the dark basements of academia. Software that operated Raman systems was often much more sophisticated than the average or even above average student could learn in the few hours of an undergraduate laboratory course. Our software was developed specifically for a teaching environment that cannot offer students hours or days to learn yet another software package. Our system is completely and effectively operated with a push of a button. We also kept this philosophy in mind when we developed our data storage choices. We chose two methods: the first is a simple ASCII file that contains the x-y spectral data; and second is the .spc format created by Thermo-Galactic. Our ASCII format is ideal for providing students with a format that can be flawlessly distributed and imported into Microsoft Excel. Students can plot their data, locate peaks, and develop their own analysis routines such as integration, and having Excel create a polynomial baseline for background correction or a least squares calibration. The .spc format provides more choices for data manipulation. It is directly imported in GRAMS (www.galactic.com) or into ACD (www.acdlabs.com). These products are offered with significant academic discounts. Both of these spectral data analysis and plotting programs offer a wide variety of means to analyze Raman spectra.

Be Prepared! DeltaNu Lab 7: Forensic Analysis of a Crime Scene Visit our website for prepared laboratories. Lab 7 features an analysis of a crime scene. It is suited for general chemistry or quantitative analysis. Students will learn about spectral calibrations, least square plots, and spectral identification. The story line is a refreshing change from drab titrations or routine qualitative analysis.
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