Resonance-enhanced deep-UV Raman spectroscopy for MDMA identification in colored ecstasy tablets

In forensic drug enforcement, there is a growing need for rapid and accurate on-site analysis of illicit substances. Effective field methods must work across a wide range of compounds, including emerging designer drugs diversifying the synthetic drug market. Spectroscopic techniques, particularly Raman spectroscopy, are promising due to their molecular specificity and portability. However, fluorescence interference limits their use for complex, colored, and/or impure samples.

This study explores the use of deep-ultraviolet resonance Raman spectroscopy (DUV-RRS) for detecting MDMA in ecstasy tablets. Using a recently commercialized 248.6 nm NeCu laser, an in-house setup was built, and its performance was compared with two commercial handheld systems and a benchtop instrument. Unlike conventional Raman systems (785–1064 nm), DUV-RRS operates in a fluorescence-free region and benefits from resonance enhancement of vibrational modes linked to MDMA's aromatic ring. This enables selective, sensitive detection, even in low-dose or inhomogeneous tablets. MDMA was reliably detected at concentrations as low as 1 % w/w, as common excipients show no resonance enhancement at this wavelength. Distinct spectral differences were observed between MDMA and analogues or isomers. Crucially, DUV-RRS yielded clean, MDMA-specific spectra for colored samples, overcoming a key limitation of conventional Raman systems.

DUV-RRS is less suited for quantitative analysis, may face challenges with multiple absorbing substances, and the system is only semi-portable. Nonetheless, as DUV source miniaturization advances, DUV-RRS becomes an increasingly viable technique. In this context, it stands out as a strong alternative to long-wavelength Raman, offering clear benefits for selective, field-deployable identification of synthetic drugs in ecstasy tablets.