Spectral trends in GC-EI-MS data obtained from the SWGDRUG mass spectral library and literature: A resource for the identification of unknown compounds

Abstract

Rapid identification of new or emerging psychoactive substances remains a critical challenge in forensic drug chemistry laboratories. Current analytical protocols are well-designed for confirmation of known substances yet struggle when new compounds are encountered. Many laboratories initially attempt to classify new compounds using gas chromatography-electron ionization-mass spectrometry (GC-EI-MS). Though there is a large body of research focused on the analysis of illicit substances with GC-EI-MS, there is little high-level discussion of mass spectral trends for different classes of drugs. This manuscript compiles literature information and performs simple exploratory analyses on evaluated GC-EI-MS data to investigate mass spectral trends for illicit substance classes. Additionally, this work offers other important aspects: brief discussions of how each class of drugs is used; illustrations of EI mass spectra with proposed structures of commonly observed ions; and summaries of mass spectral trends that can help an analyst classify new illicit compounds.

Keywords: Drug trends; GC-EI-MS; Mass spectra commonalities; Novel psychoactive substances (NPS); Seized drugs.

Fig. 1.

Provided in this figure is (A.) the core skeletal structure of barbiturates (outlined in red) and mass spectrum of pentobarbital with select proposed structural annotations [29]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the barbiturates class (n = 10). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 2.

Provided in this figure is (A.) the core skeletal structure of benzodiazepines (outlined in red) and mass spectrum of diazepam with select proposed structural annotations [33-36]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the benzodiazepines class (n = 56). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 3.

Provided in this figure is (A.) the core skeletal structure of anabolic steroids (outlined in red) and mass spectrum of testosterone with select proposed structural annotations [49,50]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the anabolic steroids class (n = 50). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 4.

Provided in this figure is (A.) the core structure of the phytocannabinoids (outlined in red) highlighting the terpenoids moiety (red box 1), the resorcinol nucleus (blue box 2) and the alkyl side chain (black box 3) and mass spectrum of Δ⁹-THC with select proposed structural annotations [67-70]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the phytocannabinoids class (n = 24). Mass spectrum obtained from SWGDRUG Mass Spectral Libraiy (version 3.10.).

Fig. 5.

Provided in this figure is (A.) the reported core structures of synthetic cannabinoids [76]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the synthetic cannabinoids class (n = 424).

Fig. 6.

Provided in this figure is (A.) the core structure of opiates (outlined in red) and mass spectrum of heroin with select proposed structural annotations [93,94]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the opiates class (n = 36). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 7.

Provided in this figure is (A.) the core skeletal structure of fentanyl (outlined in red) and mass spectrum of fentanyl with select proposed structural annotations [96-102]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the fentanyl class (n = 237). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 8.

Provided in this figure is (A.) the core skeletal structure of utopioids (outlined in red) and mass spectrum of U-47700 with select proposed structural annotations [91,100,111,112]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the utopioids class (n = 35). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 9.

Provided in this figure is (A.) core skeletal structure of the nitazenes compounds (outlined in red) and mass spectrum of metonitazene with select proposed structural annotations [14,116,117]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the nitazenes class (n = 15). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 10.

Provided in this figure is (A.) the core skeletal structure of synthetic cathinones (outlined in red) and mass spectrum of butylone with select proposed structural annotations [3,128,129]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the cathinones class (n = 229). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 11.

Provided in this figure is (A.) the core skeletal structure derived from phenethylamine (outlined in red) and mass spectrum of methamphetamine with select proposed structural annotations [133]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the amphetamines class (n = 174). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 12.

Provided in this figure is (A.) common derivatives of the phenethylamine core structure [144]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the phenethylamines class (n = 127).

Fig. 13.

Provided in this figure is (A.) the core skeletal structure of arylcyclohexylamines (outlined in red) and mass spectrum of PCP with select proposed structural annotations [147,148]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the arylcyclohexylamines class (n = 42). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 14.

Provided in this figure is (A.) the core skeletal structure of a piperazine ring (centered) with observed piperazine designer drugs (outlined in red) of the benzylpiperazine (left) and phenylpiperazines (right) structures. Also provided is a mass spectrum of BZP with select proposed structural annotations [150,151]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the piperazines class (n = 28). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 15.

Provided in this figure is (A.) the core skeletal structure of tryptamines (outlined in red) and mass spectrum of DMT with select proposed structural annotations [139,167]. Supplemental histograms depict (B.) average distribution of Low (light blue), Medium (blue), and High + Base Peak (dark blue) ions across the m/z range, (C.) average number of peaks for each RA category (excluding Ultra-Low), and (D.) frequency of the presence of a molecular ion across the RA categories for the tryptamines class (n = 57). Mass spectrum obtained from SWGDRUG Mass Spectral Library (version 3.10.).

Fig. 16.

Provided in this figure is an example mass spectrum with supplemental observations of the major ions. The occurrences of these ions correspond to the RA bins that were implemented in the code.