Preliminary study on the identification of synthetic cathinones in street seized samples by Raman spectroscopy and chemometrics

Abstract

Synthetic cathinones are new psychoactive substances that are a menace to public health worldwide and a real forensic challenge. Given the recent changes in the Brazilian legislation that bans the generic structure of these substances, the forensic workflow of drug analysis has the opportunity to speed up the arrests by in loco screening analysis. This preliminary study investigated the use of portable Raman spectrometer and chemometrics for fast, direct, and non‐destructive presumptive identification of three synthetic cathinones in seized packages and confirmatory analysis using FTIR. The 40 samples were analyzed directly and included three 3,4‐methylenodioxy substituted cathinones and other legal and illegal substances that were identified by two police forces in Brazil. Due to lack of reference Raman spectra, a purification step of the cathinone samples was performed. PCA showed that the spectral region 1,560–1750 cm−1 was the most important region for differentiating these types of cathinones from the other substances. MCR‐ALS was used to resolve the spectral mixture of signals from adulterants and identify the presence of cathinones in the seizures. The purified spectra were used as initial estimates. The concentration profiles for each component indicated significant contributions of two characteristic bands around 1,606 and 1,680 cm−1. Additionally, analysis of the optimized spectral profiles showed Raman shifts and differences in the relative intensity of those bands which allowed discrimination among the samples. Band attribution of infrared spectra confirmed the results obtained with screening method. The method proposed has potential for objective and contactless identification of seized synthetic cathinones.

Flipped detection of psychoactive substances in complex mixtures using handheld Raman spectroscopy coupled to chemometrics

“…[ 24,25,28,45 ] In cases where chemometric techniques were employed, such as PCA, detection was largely based on visual inspection of three‐dimensional scores plots and the “distance” between sample scores and those of reference standard materials for known NPS. [ 20,23,29,31,46,47 ] However, such approaches are not appropriate for the analysis of complex mixtures where the spectral profile of the sample is dominated by additives rather than the target analytes. In response to these observations, in this work, we detail below an innovative flipped detection approach based on coupling Raman spectroscopy and chemometrics for the unambiguous detection of these relevant analytes in complex mixtures.…”

“…While approaches based on spectroscopic techniques and chemometrics have been previously described, these largely rely on the spectral similarities between target analytes and NPS reference standard materials, attributing successful identification to their relative orientation in two‐ and three‐dimensional scores plots. [ 20,23,29,31 ] . Uniquely, unlike NPS, the toolbox of substances commonly used as adulterants and cutting agents remains constant, allowing for a detailed understanding of their spectral properties.…”

Portable Raman spectroscopy applied to the study of drugs of abuse

“…In comparison, Braz et al [34] in a preliminary study of the identification of synthetic cathinones in samples seized on the street, presented similar Raman spectra for samples of seized and purified cathinone (N‐ethylpentylone, ethylone, and methylbutylone). Specifically, the Raman spectrum of the purified N‐ethylpentylone sample has a shoulder band around 1625 cm −1 attributed to 3,4‐methylenedioxycatinones.…”

“…Matternich et al [33] used PCA to distinguish different synthetic cannabinoids from Raman spectra collected by laboratory and portable instrumentation. Braz et al [34] carried out a preliminary study on the seized drug of abuse for presumptive identification of three synthetic cathinone's, n‐ethylpentylone, ethylone, and methylbutylone, using the PCA and multivariate curve resolution alternating least squares (MCR‐ALS) on data acquired with a portable Raman spectrometer.…”

Identification of synthetic cathinones in seized materials: A review of analytical strategies applied in forensic chemistry

“…Raman is another vibrational technique that offers fast, sensitive, and nondestructive analyses (Braz et al, 2021; Quinn et al, 2020; Stewart et al, 2012; West & Went, 2011). Raman spectroscopy also provides elevated discriminatory power, minimal sample preparation and is less affected by humidity and interferents (Guirguis et al, 2017; Quinn et al, 2020).…”