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Two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy was evaluated for the identification and quantification of compounds in an unknown street drug sample. Using 2D COSY and HSQC techniques, heroin was successfully quantified, and the presence of 6-monoacetylmorphine (6-MAM), xylazine, and caffeine was confirmed through partial structural elucidation. These methods demonstrated the ability to differentiate structurally similar opioid analogues without reliance on reference library databases. While gas chromatography–mass spectrometry (GC–MS) remains the standard in forensic laboratories, it has limitations in de novo structural analysis and in detecting emerging analogues absent from spectral libraries. In this study, heroin and fentanyl were quantified in both simulated and actual street samples at concentrations ranging from 0.97 to 1.80 mg/mL, with errors between 0% and 34% using a 400 MHz NMR instrument. A benchtop 60 MHz NMR system also detected and quantified 56 mg/mL of heroin with a 24% error in a simulated sample. These findings support the complementary role of 2D NMR spectroscopy in forensic drug analysis in light of the opioid epidemic and the evolving drug market.
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This content will become publicly available on October 14, 2026
Quantifying the Association of Caffeine Using NMR Spectroscopy in the Chemistry Laboratory
The self-association of caffeine in solution, driven by the hydrophobic effect, is a simple example of molecular aggregation. It obeys an isodesmic association model in which each successive binding occurs with the same equilibrium constant. Here, we describe an activity for chemistry students that explores this phenomenon using nuclear magnetic resonance (NMR) spectroscopy. By analyzing concentration-dependent chemical shift changes in the 1H NMR spectra of caffeine dissolved in D2O, students are introduced to uses of NMR spectroscopy beyond structure elucidation. They gain hands-on experience in quantifying supramolecular equilibria and consider their results in the context of molecular-level interactions.
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- Award ID(s):
- 2304670
- PAR ID:
- 10646117
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Journal of Chemical Education
- Volume:
- 102
- Issue:
- 10
- ISSN:
- 0021-9584
- Page Range / eLocation ID:
- 4611 to 4615
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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