Detecting street drugs with near-infrared spectroscopy and chemometrics

The battle against the proliferation of street drugs and new psychoactive substances (NPS) has long challenged forensic science. Traditional analytical methods such as gas chromatography (GC), liquid chromatography (LC), and immunoassays, while reliable, often require significant resources and time. A groundbreaking shift, however, is emerging with the application of near-infrared spectroscopy (NIR) coupled with chemometric analysis—a method poised by researchers R. Risoluti, S. Materazzi, A. Gregori and L. Ripani to transform the detection and analysis of synthetic street drugs.

The Rise of NPS in the Illicit Market

New psychoactive substances, including synthetic cannabinoids, cathinones, piperazines, and phenethylamines, represent a fast-evolving category of designer drugs. Often marketed as "non-illegal" alternatives, these substances evade regulation while posing severe public health risks. Among these, "2C" designer drugs such as 25I-NBOMe (commonly sold as N-bomb, Smiles, or Solaris) stand out for their potent psychoactive effects. These molecules act as serotonin 5-HT2A receptor agonists, complicating predictions of their pharmacological and toxicological impact.

The variability in active ingredient concentrations and the presence of multiple psychoactive compounds in a single product further magnify the risks. This variability underscores the urgent need for rapid and reliable screening methods to identify these substances and their classes.

NIR spectroscopy is emerging as a fast, non-destructive, and cost-effective technique for preliminary drug analysis. When combined with chemometric calibration models, NIR spectroscopy allows forensic scientists to:

Rapidly identify substances: Without destroying samples, NIR can detect known and novel compounds.

Predict drug classes: Chemometric analysis provides insights into the molecular class of newly identified drugs.

Perform on-site analysis: Field deployment enables law enforcement to quickly screen confiscated samples, determining the need for further laboratory analysis.

This approach has been validated by comparing its results with established techniques like GC-MS (gas chromatography-mass spectrometry). Studies have demonstrated that NIR spectroscopy, applied to standard molecules and simulated matrices, produces accurate qualitative data. Moreover, field tests on confiscated street samples have shown that NIR is both effective and reliable, even in complex matrices.

The integration of NIR spectroscopy in forensic workflows could revolutionize the fight against NPS proliferation:

Faster decision-making: Immediate results from on-site testing guide subsequent actions, such as detailed lab analysis.

Enhanced resource allocation: Reducing reliance on time-intensive methods allows forensic labs to focus on priority cases.

Proactive response: The ability to classify new molecules on the spot equips law enforcement to adapt to the rapidly changing drug landscape.

As designer drugs continue to evolve, the forensic community must embrace technologies like NIR spectroscopy and chemometrics to stay ahead. These methods not only enhance detection capabilities but also foster a proactive stance in tackling the public health threats posed by NPS. By adopting this innovative approach, forensic science can play a pivotal role in mitigating the harm caused by illicit drugs and safeguarding communities worldwide.