GC–MS and GC–IR analysis of methylenedioxyphenylalkylamine analogues of the psychoactive 25X-NBOMe drugs

Evaluation of ATR-FTIR, HPLC-DAD, GC-MS, and GC-IR for the Analysis of 145 Street Drug Samples From Drug Checking Services

Drug checking services (DCS) are entities that allow recreational drug users to have street drug samples analyzed. Diverse analytical methods are applied for DCS, ranging from test strips to mass spectrometry (MS). This work evaluates the performance and utility of common methodologies used for DCS operating with off-site drug testing, while additionally assessing the potential of gas chromatography coupled to vapor phase infrared spectroscopy (GC-IR). Gas chromatography MS (GC-MS), GC-IR, and high-performance liquid chromatography with diode array detector (HPLC-DAD) were evaluated based on the analysis of 145 street drug samples obtained from two Swiss DCS. Additionally, attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) was applied and is briefly discussed. A combined total of 245 analytes (including adulterants and cutting agents) were detected. GC-MS presented the greatest number of detected compounds, with a sensitivity of 96% compared with the sum of all analytes, followed by HPLC-DAD with 82%, while GC-IR showed limited sensitivity with 70%. GC-IR underperformed regarding the detection of low-abundant adulterants and of the main active ingredients in strongly adulterated samples. This study discusses the limitations and strengths of the evaluated methods in the specific context of DCS, while providing insights into the occurrence of false declarations (differing analytical results compared with alleged drug identity) and the distributions of adulterants and cutting agents in street drug samples. Based on our results, complementary approaches are considered the most valuable. Finally, the promotion of comprehensive guidelines regarding the quality and suitability of analytical methods for DCS would be highly desired.

Electron ionization fragmentation studies for a series of 4-methoxymethylene benzoate esters

RATIONALE

Product ion studies and stable isotope deuterium labeling experiments provide useful data for understanding the electron ionization (EI)-mass spectroscopy (MS) fragmentation of methoxymethylene substituted benzoate esters. The methoxymethylene ether is regioisomeric with the ethoxy group and represents the two possible ether substituents of a benzene ring of C2 H5 O. Structural confirmation of these synthetic precursor materials via gas chromatography (GC)-EI-MS revealed unexpected fragment ions. The synthesis and EI-MS evaluation of some homologs and deuterated derivatives allowed for the characterization of these unique ions and their fragmentation pathways. The relative effects of the position of the oxygen of the ether side chain are the subject of this investigation.

METHODS

The desired compounds were prepared from 4-chloromethylbenzoyl chloride by alkoxide displacement followed by transesterifications and the deuterated analogs were prepared similarly. The compounds were separated by capillary GC and their MS fragmentation evaluated in EI, MS/MS and chemical ionization experiments.

RESULTS

The methoxymethylene-substituted benzoate esters yield major fragment ions from the loss of the alkyl group from the ether as well as alkoxy group loss from the ester or ether portion of the molecule. The loss of the alkyl group from the ether followed by loss of the ester alkoxy group as the corresponding alcohol yielded the unique cation at m/z 133 for all compounds. The identity of the major ions was confirmed by product ion and deuterium labeling studies and possible mechanisms of fragment ion formation are described.

CONCLUSIONS

The aliphatic oxygen of the alkoxymethylene group plays a much more active role in the EI-MS fragment formation profile than the direct aromatic ring linked oxygen of the ethoxy group. Thus, yielding a greater variety of characteristic fragments. The m/z 133 ion is unique to this class of compounds and does not have an equivalent pathway for the regioisomeric ethoxy series.

An interlaboratory study to evaluate the utility of gas chromatography-mass spectrometry and gas chromatography-infrared spectroscopy spectral libraries in the forensic analysis of fentanyl-related substances

Synthetic opioids such as fentanyl account for over 71,000 of the approximately 107,000 overdose deaths reported in the United States in 2021. Fentanyl remains the fourth most identified drug by state and local forensic laboratories, and the second most identified drug by federal laboratories. The unambiguous identification of fentanyl-related substances (FRS) is challenging due to the absence or low abundance of a molecular ion in a typical gas chromatography-mass spectrometry (GC-MS) analysis and due to a low number of fragment ions that are similar among the many potential isomers of FRS. This study describes the utility of a previously reported gas chromatography-infrared (GC-IR) library for the identification of FRS within a blind, interlaboratory study (ILS) involving seven forensic laboratories. Twenty FRS reference materials, including those with isomer pairs in the library, were selected based on either their presence in the NIST library and/or some similarity of the mass spectra information produced. The ILS participants were requested to use the Florida International University (FIU) GC-MS and GC-IR libraries supplied by FIU to search for matches to their unknown spectra generated from in-house GC-MS and GC-IR analysis. The laboratories reported improvement in the positive identification of unknown FRS from ~75% using GC-MS alone to 100% correct identification using GC-IR analysis. One laboratory participant used solid phase IR analysis, which produced spectra incompatible with the vapor phase GC-IR library to generate a good comparison spectrum. However, this improved when searched against a solid phase IR library.

Portable near infrared spectroscopy for the isomeric differentiation of new psychoactive substances

Rapid and efficient identification of the precise isomeric form of new psychoactive substances (NPS) by forensic casework laboratories is a relevant challenge in the forensic field. Differences in legal status occur for ring-isomeric species of the same class, thus leading to different penalties and judicial control. Portable systems such as near-infrared (NIR) spectroscopy recently emerged as suitable techniques for the on-scene identification of common drugs of abuse such as cocaine, MDMA and amphetamine. This way, the overall forensic process becomes more efficient as relevant information on substance identity becomes available directly at the scene of crime. Currently, no NIR-based applications exist for the rapid, on-scene detection of NPS isomers. Herein, we present the differentiation of cathinone and phenethylamine-type NPS analogues based on their NIR spectrum recorded in 2 seconds on a portable 1350 - 2600 nm spectrometer. A prior developed data analysis model was found suitable for the identification of the methylmethcathinone (MMC) isomers 2-MMC, 3-MMC and 4-MMC. In 51 mixtures and 22 seized casework samples, the correct isomeric form was detected in all cases except for a few mixtures with an active ingredient content of 10 wt%. These results show the feasibility of on-site NPS detection as presumptive test performed directly at the scene of crime with a small size NIR-spectrometer. Additionally, in the illicit drug analysis laboratory the combination of NIR and GC-MS analysis might be suitable for robust identification of NPS isomers and analogues.