Characterization of new psychoactive substances by integrating benchtop NMR to multi-technique databases

Nuclear Magnetic Resonance Spectroscopic Characterization and Determination of the New Psychoactive Substance Benzylone: Application in a Biological Fluid

New psychoactive substances (NPS)-designed to mimic various legal or illegal substances-are an emerging worldwide health problem. Their identification and quantification in either complex seized samples or powders are critical; moreover, their determination in biological fluids is an intriguing goal in the forensic toxicology field. Synthetic cathinones are one of the most important groups among NPS. The current paper was designed as a pilot study to investigate the application of NMR techniques to identify and quantify unknown NPS compounds in deuterated dimethyl sulfoxide (DMSO-d6) and in urine using the synthetic cathinone benzylone (3,4-methylenedioxy-N-benzylcathinone, BMDP) as a pilot compound. In the first part of our study, nuclear magnetic resonance (NMR) spectroscopic characterization was performed using 1D and 2D homonuclear and heteronuclear NMR spectroscopic methods as long as diffusion ordered spectroscopy (DOSY). Following the above, the assignment of benzylone in DMSO-d6 was performed, and a distinct spectroscopic pattern was proposed. In the second part of our study, a NMR spectroscopic approach was applied for benzylone identification and quantification in a spiked with benzylone urine. Following the above, the assignment of benzylone in spiked urine was performed. A distinct pattern of the H11, H14, H15, and H8 signals on the 1H NMR spectra was observed and suggested as a "NMR spectroscopic pattern/signature" enabling the identification of benzylone moieties in urine. On the other hand, the applied NMR techniques showed low sensitivity in quantitating benzylone in spiked urine. Overall, our results are promising in using NMR for structure determination of unknown compounds in urine.

Hyperpolarised benchtop NMR spectroscopy for analytical applications

Benchtop NMR spectrometers, with moderate magnetic field strengths (B0=1-2.4T) and sub-ppm chemical shift resolution, are an affordable and portable alternative to standard laboratory NMR (B0≥7T). However, in moving to lower magnetic field instruments, sensitivity and chemical shift resolution are significantly reduced. The sensitivity limitation can be overcome by using hyperpolarisation to boost benchtop NMR signals by orders of magnitude. Of the wide range of hyperpolarisation methods currently available, dynamic nuclear polarisation (DNP), parahydrogen-induced polarisation (PHIP) and photochemically-induced dynamic nuclear polarisation (photo-CIDNP) have, to date, shown the most promise for integration with benchtop NMR for analytical applications. In this review we provide a summary of the theory of each of these techniques and discuss examples of how they have been integrated with benchtop NMR detection. Progress towards the use of hyperpolarised benchtop NMR for analytical applications, ranging from reaction monitoring to probing biomolecular interactions, is discussed, along with perspectives for the future.

Non-uniform sampling to enhance the performance of compact NMR for characterizing new psychoactive substances

Efficient and robust analytical methods are needed to improve the identification and subsequent regulation of new psychoactive substances (NPS). NMR spectroscopy is a unique method able to determine the structure of small molecules such as NPS even in mixtures. However, high-field NMR analysis is associated with expensive purchase and maintenance costs. For more than a decade, compact NMR spectrometers have changed this paradigm. It was recently shown that a dedicated analytical workflow combining compact NMR and databases could identify the molecular structure of NPS, in spite of the lower spectral dispersion and sensitivity of compact spectrometers. This approach relies on 1H-13C HSQC to both recognize NPS and elucidate the structure of unknown substances. Still, its performance is limited by the need to compromise between resolution and experiment time. Here, we show that this strategy can be significantly improved by implementing non-uniform sampling (NUS) to improve spectral resolution in the 13C dimension of HSQC at no cost in terms of experiment time. Gains in the range of 3 to 4 in resolution are achieved for pure NPS and for a mixture. Finally, 2D HSQC with NUS was applied to improve the identification of NPS with the assistance of databases. The resulting method appears as a useful tool for the characterization of NPS in mixtures, which is essential for forensic laboratories.

DFT-Spectroscopy Integrated Identification Method on Unknown Terrorist Chemical Mixtures by Incorporating Experimental and Theoretical GC-MS, NMR, IR, and DFT-NMR/IR Data

In the event of a chemical attack, the rapid identification of unknown chemical agents is critical for an effective emergency response and treatment of victims. However, identifying unknown compounds is difficult, particularly when relying on traditional methods such as gas and liquid chromatography-mass spectrometry (GC-MS, LC-MS). In this study, we developed a density functional theory and spectroscopy integrated identification method (D-SIIM) for the possible detection of unknown or unidentified terrorist materials, specifically chemical warfare agents (CWAs). The D-SIIM uses a combination of GC-MS, nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, and quantum chemical calculation-based NMR/IR predictions to identify potential CWA candidates based on their chemical signatures. Using D-SIIM, we successfully verified the presence of blister and nerve agent simulants in samples by excluding other compounds (ethyl propyl sulfide and methylphosphonic acid), which were predicted to be candidates with high probability by GC-MS. The findings of this study demonstrate that the D-SIIM can detect substances that are likely present in CWA mixtures and can be used to identify unknown terrorist chemicals.