High-field and benchtop NMR spectroscopy for the characterization of new psychoactive substances

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.

A screening method for the quantitative determination of selective androgen receptor modulators (SARMs) in capsules by high resolution 19F- and 1H-NMR spectroscopy

A new method for rapid determination of the content of selective androgenic receptor modulators (SARMs) andarine, cardarine, ligandrol, ostarine and S-23 in capsules by 1H- and 19F-high resolution nuclear magnetic resonance spectroscopy was described and validated. Specificity, linearity, accuracy, precision, detection and quantification limits were considered as validation parameters. Full 1H-, 13C- and 19F-NMR structural assignment of the SARMs is provided as a tool for self-standing identification without a reference standard. Amounts of 7-15 mg of SARMs/capsule were detected in different products with an intermediate precision of 0.8-1.7% in 4 to 20 minutes of analysis time. The validation results and rapidity of analysis confirm the applicability of the method for large-scale screening. The statistical analysis of the results from 19F- and 1H-quantitative NMR showed that both approaches were equally effective, thus expanding the potential use of the methodology to non-fluorinated SARMs. At present, no SARM has been approved for human consumption; however, SARMs are actually used by bodybuilders and recreational athletes, who purchase them even though the risk-benefit ratio of these molecules has not been definitively established.

Synthesis, characterization and differentiation of the structural isomers of valine and tert-leucine derived synthetic cannabinoids

The identification of the synthetic cannabinoids receptor agonists (SCRAs) has always posed a great challenge to drug testing laboratories with slight structural modifications aimed at evading drug legislation. In addition, the most prevalent synthetic cannabinoids have valine and tert-leucine amino acid moieties where re-arrangement of the carbon chains can result in structural isomers that are very similar to the parent synthetic cannabinoids. This makes their analysis and identification challenging, and the problem is compounded with the difficulty in purchasing reference standards quickly and a lack of literature for comparison. Therefore, in this investigation, four series of synthetic cannabinoids (AB-PINACA, AB-CHMINACA, MMB-FUBINACA and 5-fluoro-MDMB-PINACA) and their alkyl chain structural isomers at the amino acid moieties were synthesized and characterized using various analytical techniques-gas chromatography-mass spectrometry (GC-MS), gas chromatography-infrared detection (GC-IRD) and nuclear magnetic resonance (NMR) spectroscopy to evaluate the ability of each analytical technique to differentiate the respective isomers for their identification. A total of 12 isomers were synthesized and analysed together with the four parent synthetic cannabinoids. NMR was able to differentiate between all the compounds, whereas GC-IRD was able to discern between most of the synthetic cannabinoids and their isomers. GC-MS had the least discriminating power and was not able to differentiate some of the compounds that has very similar mass spectra. The results from this work will be useful to other drug testing laboratories that are facing the identification of related synthetic cannabinoids.

The differentiation of N-butyl pentylone isomers using GC-EI-MS and NMR

Forensic laboratories are faced with an ever-expanding seized drug landscape including the increasing prevalence of novel psychoactive substances (NPS), such as synthetic cathinones, that have varying potencies and scheduling. This study demonstrates a combined gas chromatography-electron ionization-mass spectrometry (GC-EI-MS) and nuclear magnetic resonance (NMR) spectroscopy approach for the differentiation of N-butyl pentylone isomers based on distinct retention times, characteristic EI mass spectra, and NMR characterization. Retention time reproducibility was assessed from 60 replicate measurements for each isomer over the course of a month. In addition, the effect of the mass spectrometer tune and the stability of an identified characteristic ion ratio using spectral data from ± 1 scan on either side of the peak apex were also statistically assessed using Welch's ANOVA testing. The presence of diastereomers for N-sec-butyl pentylone was identified using the developed GC-EI-MS method, which was confirmed using one-dimensional and two-dimensional NMR spectroscopy. The retention time reproducibility of the chromatographic method was ± 0.076% or less over the course of a month. An identified characteristic ion ratio between the abundance of the fragment ion at m/z 128 and the fragment ion at m/z 72 enabled the differentiation of the four N-butyl pentylone isomers, even when accounting for the effect of the mass spectrometer tune and mass spectral scans used to calculate the characteristic ion ratio. The 95% confidence interval mean abundance ratio of the fragment ions at m/z 128 and m/z 72 was 17.14 ± 0.14 for N-butyl pentylone, 6.44 ± 0.05 for N-isobutyl pentylone, 3.38 ± 0.02 for N-sec-butyl pentylone, and 0.75 ± 0.01 for N-tert-butyl pentylone. These results highlight the capabilities of a combined GC-EI-MS and NMR approach for the differentiation and characterization of synthetic cathinone isomers.

Indazole-derived synthetic cannabinoids: Absolute configuration determination and structure characterization by circular dichroism and DFT calculations

An increasing number of products containing synthetic cannabinoids pose a growing crisis to public health worldwide. Recently, a rising number of cases of serious adverse health effects, intoxications, and death cases associated with synthetic cannabinoids were reported. The current study represents the comprehensive structural analysis of three new synthetic cannabinoids (AB-, ADB- and AMB-FUBINACA) in solution investigated by electronic and vibrational circular dichroism together with the conventional methods of infrared and ultraviolet absorption spectroscopy, all supported by the density functional theory (DFT) calculations. The best level of theory to reproduce the experimental wavenumbers and wavelengths was found to be the B3PW91 method with a 6-311++G(d,p) basis set including the implicit solvent effect simulation. Very good agreement between the experimental and simulated spectra allowed us to determine the absolute configuration and a detailed interpretation of the IR absorption, VCD, ECD and UV spectra of AB-, ADB- and AMB-FUBINACA. In addition, the HOMO and LUMO electronic transitions were calculated.

New trends of new psychoactive substances (NPS)-infused chocolate: Identification and quantification of trace level of NPS in complex matrix by GC-MS and NMR

For the first time, the identification and quantification of trace level of new psychoactive substances (NPS) in a complex chocolate matrix have been reported. Since the beginning of 2022, suspected NPS-infused chocolate samples confiscated in inbound packages have been continuously sent to our laboratory for analysis. The qualitative gas chromatography-mass spectrometry (GC-MS) results were verified by ¹H nuclear magnetic resonance (¹H NMR) and ¹⁹F NMR to distinguish between potential aromatic isomers. A total of 11 NPS including deoxymethoxetamine, 3-OH-PCP, 6-APB, 4-APB, 4-OH-MiPT, 3-FEA, 2-FEA, 3-MMC, bromazolam, 2-FDCK, and ADB-BUTINACA were detected in 65 seized chocolate samples. A general ¹H quantitative NMR (¹H qNMR) method for quantification of 297 types of NPS in complex chocolate matrixes was devised for the first time after rigorous analysis of various critical features of merit, including suitable deuterated solvent, internal standard, quantitative peaks, and instrument acquisition parameters. Validation of the method using six different types of NPS afforded limits of detection of 0.05-0.1 mg/mL, limits of quantification of 0.01-0.03 mg/mL, repeatability and reproducibility lower than 0.5% and 3.6%, recoveries of 91.7%∼104.4%, and absence of matrix effect. The quantitative analysis of 65 seized chocolate samples by ¹H qNMR and ¹⁹F qNMR showed that the content of NPS was in the range of 0.5 mg/g∼44.1 mg/g. Generally, the developed qNMR method was simple, fast, precise, and can be performed without reference materials of NPS. Since the type and content of NPS are relatively random, chocolate consumers will face huge health risks. Therefore, this new trend of NPS-infused chocolate deserves and requires more attention from national NPS monitoring departments as well as forensic laboratories.

Challenges in Drug Surveillance: Strengthening the Analysis of New Psychoactive Substances by Harmonizing Drug Checking Services in Proficiency Testing

BACKGROUND

Drug checking is a proven harm reduction strategy and provides real-time information on the market of new psychoactive substances (NPS). It combines chemical analysis of samples with direct engagement with people who use drugs (PWUD), giving the ability to increase preparedness and responsiveness towards NPS. Next to that, it supports rapid identification of potential unwitting consumption. However, NPS cause a toxicological battle for the researchers, as factors such as the unpredictability and quick shift of the market complicate the detection.

METHODS

To evaluate challenges posed towards drug checking services, proficiency testing was set up to evaluate existing analytical techniques and investigate the capability to correctly identify circulating NPS. Twenty blind substances, covering the most common categories of substances, were analyzed according to the existing protocols of the existing drug checking services, including several analytical methods such as gas chromatography-mass spectrometry (GC-MS) and liquid chromatography with diode array detector (LC-DAD).

RESULTS

The proficiency test scores range from 80 to 97.5% accuracy. The most common issues and errors are mainly unidentified compounds, presumably due to no up-to-date libraries, and/ or confusion between structural isomers, such as 3- and 4-chloroethcathinone, or structural analogs, such as MIPLA (N-methyl-N-isopropyl lysergamide) and LSD (D-lysergic acid diethylamide).

CONCLUSIONS

The participating drug checking services have access to adequate analytical tools to provide feedback to drug users and provide up-to-date information on NPS.

An overview of New Psychoactive Substances (NPS) in northeast Brazil: NMR-based identification and analysis of ecstasy tablets by GC-MS

The actual illicit market for synthetic drugs is characterized by a wide variety of psychoactive substances of different chemical and pharmacological classes, such as amphetamine-type stimulants and new psychoactive substances. The knowledge about its chemical composition, as well as the nature and quantity of the active substances present, is important for emergency care in intoxication cases by these substances and to establish adequate chemical and toxicological analysis procedures in forensic laboratories. The aim of this work was to study the prevalence of amphetamine-type stimulants and new psychoactive substances in the states of Bahia and Sergipe, in the northeast region of Brazil, involving samples of drugs seized by the local police forces from 2014 to 2019. In a total of 121 seized and analyzed samples, in which ecstasy tablets predominated (n = 101), nineteen substances were identified using GC-MS and ¹D NMR techniques, comprising classical synthetic drugs and new psychoactive substances (NPS). In order to determine the composition of ecstasy tablets, an analytical method based on GC-MS was applied after validation. Analyzes of 101 ecstasy tablets showed that MDMA was the main substance, being found in 57% of the samples, in amounts between 27.3 and 187.1 mg per tablet. In addition, mixtures of MDMA, MDA, synthetic cathinones and caffeine were observed in 34 samples. These results demonstrate that the variety of substances found and the composition of seized materials in northeast Brazil is similar to other studies carried out previously in other Brazilian regions.

The application of 19F NMR spectroscopy for the analysis of fluorinated new psychoactive substances (NPS)

In this study, fluorine-19 nuclear magnetic resonance spectroscopy (¹⁹F NMR) served as a highly specific tool for identification of fluorinated new psychoactive substances (NPS) as well as a suitable analytical method for the accurate quantification of fluorinated NPS in different seized samples. In the first part of the study, ¹⁹F NMR spectroscopy of a number of different fluorinated NPS, including 51 synthetic cannabinoids, 8 synthetic cathinones, 7 phenethylamines, 8 fentanyl analogues, and 9 other types of compounds was conducted. The chemical shifts and multiplet of the primary fluorides (RCH₂F), fluorobenzenes (ortho-ArF, meta-ArF, and para-ArF), and trifluoromethylbenzenes (ArCF₃) were discussed in detail to illustrate the role of ¹⁹F signals as special fingerprints in assisting the structure identification of fluorine-containing NPS. To the best of our knowledge, this study is the largest evaluation of fluorinated NPS compounds by ¹⁹F NMR. The second part of this study dealt with the problems encountered in the ¹⁹F quantification procedure and the criteria to be considered for successful quantification by ¹⁹F NMR. General high field (HF)- and low field (LF)- ¹⁹F qNMR methods for the quantification of fluorinated NPS were established after the thorough discussion of NMR spectrum acquisition and processing parameters such as: transmitter frequency offset (O1P), spin-lattice relaxation time (T₁), and different baseline correction methods. The limit of quantifications (LOQs) for HF-¹⁹F qNMR varied between 0.1 mg/mL and 0.2 mg/mL, and for LF-¹⁹F qNMR varied between 1.0 mg/mL and 2.0 mg/mL. The limit of detections (LODs) for HF-¹⁹F qNMR varied between 0.03 mg/mL and 0.06 mg/mL, and for LF-¹⁹F qNMR varied between 0.3 mg/mL and 0.6 mg/mL. Finally, the developed methods were applied for the quantification of fluorinated-NPS in seventeen herbal blends, e-liquid, tablet, and powder NPS seizures.

Predicting Mandarin Fruit Acceptability: From High-Field to Benchtop NMR Spectroscopy

Recent advances in nuclear magnetic resonance (NMR) have led to the development of low-field benchtop NMR systems with improved sensitivity and resolution suitable for use in research and quality-control laboratories. Compared to their high-resolution counterparts, their lower purchase and running costs make them a good alternative for routine use. In this article, we show the adaptation of a method for predicting the consumer acceptability of mandarins, originally reported using a high-field 400 MHz NMR spectrometer, to benchtop 60 MHz NMR systems. Our findings reveal that both instruments yield comparable results regarding sugar and citric acid levels, leading to the development of virtually identical predictive linear models. However, the lower cost of benchtop NMR systems would allow cultivators to implement this chemometric-based method as an additional tool for the selection of new cultivars.

Comparative study of the analysis of seized samples by GC-MS, 1H NMR and FT-IR spectroscopy within a Night-Time Economy (NTE) setting

Rapid analysis of surrendered or seized drug samples provides important intelligence for health (e.g. treatment or harm reduction), and custodial services. Herein, three in-situ techniques, GC-MS, ¹H NMR and FT-IR spectroscopy, with searchable libraries, are used to analyse 318 samples qualitatively, using technique specific library-based searches, obtained over the period 24th - 29th August 2019. 259 samples were identified as consisting of a single component, of which cocaine was the most prevalent (n = 158). Median match scores for all three techniques were ≥ 0.84 and showed agreement except for metformin (n = 1), oxandrolone (identified as vitamin K by IR (n = 4)), diazepam (identified as zolpidem by FT-IR (n = 2)) and 2-Br-4,5-DMPEA (n = 1), a structural isomer of 2C-B identified as a polymer of cellulose (cardboard) by FT-IR. 51 samples were found to consist of two or more components, of which 49 were adulterated cocaine samples (45 binary and 4 tertiary samples). GC-MS identified all components present in the 49 adulterated cocaine samples, whereas IR identified only cocaine in 88 % of cases (adulterant only = 12 %). The breakdown for ¹H NMR spectroscopy was all components identified (51 %), cocaine only (33 %), adulterant only (10 %), cocaine and one adulterant (tertiary mixtures only, 6 %).

Recent Applications of Benchtop Nuclear Magnetic Resonance Spectroscopy

Benchtop nuclear magnetic resonance (NMR) spectroscopy uses small permanent magnets to generate magnetic fields and therefore offers the advantages of operational simplicity and reasonable cost, presenting a viable alternative to high-field NMR spectroscopy. In particular, the use of benchtop NMR spectroscopy for rapid in-field analysis, e.g., for quality control or forensic science purposes, has attracted considerable attention. As benchtop NMR spectrometers are sufficiently compact to be operated in a fume hood, they can be efficiently used for real-time reaction and process monitoring. This review introduces the recent applications of benchtop NMR spectroscopy in diverse fields, including food science, pharmaceuticals, process and reaction monitoring, metabolomics, and polymer materials.

Synthetic cannabinoids in e-liquids: A proton and fluorine NMR analysis from a conventional spectrometer to a compact one

The ¹H NMR profiles of 13 samples of e-liquids supplied by French customs were obtained with high-field and low-field NMR. The high-field ¹H NMR spectra allowed the detection of matrix signals, synthetic cannabinoids, and flavouring compounds. Quantitative results were obtained for the five synthetic cannabinoids detected: JWH-210, 5F-MDMB-PICA, 5F-ADB, 5F-AKB48, and ADB-FUBINACA. Conventional GC-MS analysis was used to confirm compound identification. Fluorine-19 NMR was proposed for the quantification of fluorinated synthetic cannabinoids and was successfully implemented on both 400 MHz and 60 MHz NMR spectrometers. This study based on few examples explored the potentiality of low-field NMR for quantitative and quantitative analysis of synthetic cannabinoids in e-liquids.