In this research, we created a forensic-themed case study using liquid chromatography (LC) methodology to challenge upper-level undergraduate understanding of LC applications and instrumental methods. Students are given several chromatograms that show separation of known analgesics under varied instrumental parameters. With this information, they are asked to select and justify optimized parameters for separation. Using their conclusions, they can work to identify unlabeled “unknown” compounds from another set of chromatograms. Specifically, three different reversed phase columns were used to separate seven common over-the-counter analgesic compounds, including acetaminophen (Tylenol), aspirin, and ibuprofen (Motrin). Mobile phase polarity and pH were varied to optimize the separation on each column. A diode array detector allowed for observation of multiple wavelengths. Students should discover that C18-PFP and RP-Amide columns were able to resolve all seven peaks, yet differences in selectivity led to distinct analyte elution orders. The C18 was unable to provide sufficient separation of these seven compounds and should therefore be ruled out for determination of this mixture composition. Students will be asked to communicate their results to both specialized (scientific) and general (judicial) audiences.

Investigation of analgesic separations: A forensic case study

253rd National Meeting (2017)

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