Early detection of emerging street drugs by near infrared spectroscopy and chemometrics
Graphical abstract
Introduction
New psychoactive substances (NPS), are a large group of synthetic molecules frequently found in the street market as drugs of abuse. Typical examples are synthetic cannabinoids, cathinones, piperazines, and tryptamines. In addition, new drugs are currently proposed, like molecules derivatives of phenethylamines [1] and most of them are not yet completely controlled by international drug conventions, and may pose a public health threat. In particular, the risk is strictly related to the difficulty of predicting the actual consumed dose, due to variability of active ingredients concentration in consumed products, and as opposed to those claimed by the manufacturer. In addition, the difficulty of predicting the actual pharmacological and toxicological effects related to the simultaneous consumption of different psychoactive ingredients contained in single products, requires a rapid screening and identification of these materials.
Recently, a class of “2C” designer drugs, dimethoxyphenyl-N-[(2-methoxyphenyl) methyl]ethanamine) derivatives have become easily obtainable over the internet, particularly 2-(4-iodo-2,5-dimethoxyphenyl)-N-[(2-methoxyphenyl)methyl]ethanamine (25I-NBOMe). Blotter papers containing 25I-NBOMe appeared on the designer drug market in 2011 [2] sold under various names including 25I, INB-MeO, N-bomb, Smiles, Solaris and Cimbi-5. These N-benzyl phenylethylamine derivatives are potent serotonin 5-HT2A receptor agonists [3], [4], [5].
Investigation of these (often not illegal) substances by official methods of analysis is usually performed by applying immunoassays [6], gas chromatography (GC) [7], [8], capillary electrophoresis (CE) [9], [10] or liquid chromatography (LC) [11], [12], [13], [14].
Nowadays it is becoming always more important to develop fast, reproducible and easy-to-use preliminary methods to allow the “on street” early detection to decide the following official analysis in forensic laboratories.
In addition, it should be very useful the possibility to have techniques able to give suggestions on the class of molecules when a new drug is found on the market.
Near-infrared reflectance spectroscopy (NIRs) proved to be fast and precise to identify and quantify substances of abuse without destroying the samples [15].
In this work, NIR spectroscopy combined with chemometrics was tested to be proposed as a useful tool to easily and early detect new drug molecules in real street samples. In addition, results demonstrated that NIRs application, supported by chemometrics, could in addition predict the class of molecule of new drugs. Qualitative data was consequently the main focus of this approach.
To this end, standard molecules was analyzed as such and in simulated matrices, to check the matrix influence on the spectroscopic signal and to obtain referring scores plots. Validation tests were performed on real confiscated samples, in parallel analyzed by GC–MS.
Section snippets
Samples
Standard molecules were purchased from LGC Standards (Italian customer – Milano) or kindly provided by Carabinieri RIS (Scientific Investigation Department).
Drug samples in real matrices (either containing illegal known substances or new molecules) were obtained from samples confiscated by Carabinieri as herbal spices and blotter papers. The complete list with related details is reported in Table 1.
Sample preparation
No sample preparation was necessary for NIRs measurements, as either the standards or the real
Results and discussion
The investigated molecules were selected from recent seizures by low enforcement in our country including JWH series and analogues as the AKB48, a synthetic cannabinoid belonging to the family of indazoles. In addition, three different molecules belonging to two different class of phenethylamines (Fig. 2), the NBOMe series (N-2-methoxybenzyl derivatives of phenethylamine), 25-I-NBOMe and 25-C-NBOMe, and 2-CP were also considered because of their similar chemical structure and because were found
Conclusions
Attempts to develop effective and inexpensive techniques for the early detection of new illicit drugs continue to play a central role in forensic investigations.
Combining information from the NIR spectroscopy and chemometrics we proposed a new promising approach for the screening of seized emerging drugs. Spectroscopic techniques present further indisputable advantages compared to the other fingerprinting technique examined. They are, in fact, time-saving, as they require no or minimal sample
Acknowledgments
The authors would like to thank the Scientific Investigation Department (Carabinieri-RIS) of Rome for providing us with standard molecules and confiscated real samples supporting this study.
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