Analysis of Black Market Bath Salts Using GC-IR

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Cathinones, commonly known as ‘bath salts’, are a large class of compounds belonging to the family of novel psychoactive substances (NPS).

Cathinones are often marketed as alternatives to more widely known recreational drugs due to their stimulant properties.1 In addition to being an alternative stimulant for users, cathinones have also been detected as substitutes or adulterants for common recreational drugs such as MDMA tablets (commonly known as “Ecstasy”). increase.2

A wide variety of structurally closely related compounds characterize the cathinone class of substances, including structural isomers.

Some structural isomers may be classified differently than other cathinones, depending on the regulatory framework surrounding the drug. Therefore, forensic laboratories ultimately need analytical methods that allow forensic annotation of the exact isomeric structures of cathinones.

Accurate chemical structure information is also essential in the context of chemical analysis of drug samples, as structural isomers can produce different pharmacological effects.

Structural isomers are often indistinguishable when using mass spectrometry, as they can lead to mass fragmentation patterns and similar retention times. Infrared (IR) spectroscopy has proven to be very valuable, for example, where substitutions at different positions on aromatic rings give rise to different IR absorption patterns.3

Common IR techniques such as Attenuated Total Reflectance Fourier Transform IR Spectroscopy (ATR-FTIR) and Near Infrared Spectroscopy (NIR) are suitable for analyzing pure compounds. However, mixtures are often encountered when analyzing recreational drugs.

On the black market, investigated drugs are often found to contain admixtures, cutting agents or, in the case of tablets, various excipients and additional tablet fillers. This naturally limits the reliability of analytical results obtained by direct IR techniques. However, these problems can be overcome by incorporating IR spectroscopy into chromatographic techniques such as gas chromatography (GC).

In this article, the structural isomers 3-methylmethcathinone (mephedrone; 3-MMC), 4-methylmethcathinone (mephedrone; 4-MMC) and 3-chloromethcathinone (clophedrone, 3-CMC) and 4 -Chloromethcathinone (crefedrone, 4-CMC) (see Figure 1).

Chemical structures of studied cathinones.

Figure 1. Chemical structures of studied cathinones.Image Credit: Thermo Fisher Scientific – Chemical Analysis


The Department of Forensic Toxicology and Chemistry at the Basel University Forensic Institute analyzed several experimental samples consisting of tablets and powders (see Figure 2).

1-2 mg of pure reference standard and 10 mg of homogenized black market sample were weighed and dissolved in 1 mL of 0.5 M NaOH, thereby generating the drug free base. GC-IR analysis was performed using a Thermo Scientific Trace 1310 gas chromatograph hyphenated to a Thermo Scientific™ Nicolet™ iS50 FTIR spectrometer.

The FTIR system is equipped with an iS50 GC-IR module and was performed using a liquid nitrogen cooled MCT-A detector. Preliminary separation of compounds was achieved using his OPTIMA 5 MS GC column (30 m × 0.25 mm, 0.25 μm film thickness) obtained from Macherey Nagel (Oensingen, Switzerland).

The GC system configuration used a split/splitless injector maintained at 280 °C and operated in splitless mode with an injection volume of 1 μL. Helium was used as carrier gas at a flow rate of 1.5 mL/min.

The GC temperature program started at 90 °C and held for 1 minute. The next step was ramping at 45 °C/min to a final temperature of 270 °C. This temperature was then maintained for 5 minutes, ending with a total run time of 17.4 minutes.

The transfer line and flow cell temperatures of the GC-IR module were increased to 270 °C and 280 °C, respectively. Then at 8 cm he generated a series file at 4 scans per second.-1 Solved. Background was measured (100 scans) before each sample injection.

Thermo Scientific, Inc. Omnic The software was used to perform data analysis by library search against in-house libraries. For library construction, we used certified reference materials obtained from Lipomed (Arlesheim, Switzerland) or provided by the Zurich Institute for Forensic Medicine (Zurich, Switzerland). Additionally, we utilized his TBI GC IR gas phase library from Thermo Fisher Scientific.Four

Photo of sample 4.

Figure 2. Photo of sample 4.Image Credit: Thermo Fisher Scientific – Chemical Analysis

table 1. Summary of analysis results.Source: Thermo Fisher Scientific – Chemical Analysis

exterior result match
sample 1 white powder 4-CMC 98.46
sample 2 white powder 4-MMC 99.61
sample 3 white powder 3-MMC 98.92
sample 4 yellow tablet 4-MMC

Results and discussion

Table 1 summarizes the results for all samples investigated. A clear distinction of the investigated cathinones was made possible by GC-IR, demonstrated by high concordance coefficients (>97) for unambiguous identification. The high discriminatory power of IR spectroscopy is evident when comparing the reference spectra of 3-CMC and 4-CMC shown in Figure 2 and 3-MMC and 4-MMC shown in Figure 3.

IR spectra of 3-CMC and 4-CMC (top), and 3-MMC and 4-MMC (bottom).

Figure 3. IR spectra of 3-CMC and 4-CMC (top), and 3-MMC and 4-MMC (bottom).Image Credit: Thermo Fisher Scientific – Chemical Analysis

3-CMC was detected in the white powder of sample 1. The cathinones detected in samples 2 and 3 were 4-MMC and 3-MMC, respectively. Finally, sample 4 resembled common ecstasy tablets, but GC-IR analysis showed it to be a mixture of MDMA and 4-MMC. When using direct IR techniques, mixtures of compounds often influence the correct compound annotation, compromising the reliability of the results.

However, both MDMA and 4 MMC could be detected quickly, reliably, and easily using GC-IR, as seen on the tablet in sample 3.

Within the Gram-Schmidt profile, both compounds showed distinct peaks. Using the GC Identify command of Mercury GC analysis software eliminated subjective data interpretation and fully automated the annotation of MDMA and 4-MMC (Figure 4).

Automated OMNIC Mercury GC data analysis results for sample 4.

Automated OMNIC Mercury GC data analysis results for sample 4.

Figure 4. Automated OMNIC Mercury GC data analysis results for sample 4. Image credit: Thermo Fisher Scientific – Chemical Analysis

Comparing the 3-CMC and 4-CMC reference spectra shown in Figure 2 with the 3-MMC and 4-MMC reference spectra shown in Figure 3, this can be clearly confirmed by IR spectroscopy.


Cathinones continue to emerge in the recreational drug market, requiring reliable methods to unambiguously and rapidly identify structural isomers of this compound class from a forensic perspective.

Thermo Fisher Scientific’s GC-IR module enables easy, rapid, and reliable detection of cathinones in drug samples found on the black market. In addition to pure powders, more challenging samples such as tablets and mixtures of compounds have also been successfully analyzed.

Furthermore, processing and interpretation of the data was relatively straightforward when applying the Mercury GC analytical software.

References and further information

  1. Goncalves, JL; Alves, Vermont. Aguiar, J. Teixeira, HM. Câmara, JS Synthetic cathinones: an evolving class of new psychoactive substances. A critical review in toxicology 2019, 49, 549-566, Doi: 10.1080/10408444.2019.1679087.
  2. Oliver, CF. Paramar, JJ. Salomone, A. Simmons, South Carolina. Philosine Khalid, HL; Stokes McCloskey, N. Rawls, SM Synthetic cathinone contamination of illicit drugs. psychopharmacology 2019, 236, 869-879, doi: 10.1007/s00213-018-5066-6.
  3. Avidala, Y. Deruiter, J. Clark, CR GC-MS, GC-MS/MS and GC-IR identification of deoxycathinone derivatives: cyclic tertiary amines associated with MDPV. chromatography journal B 2017, 1048, 38-48, Doi:
  4. Application Note – Bath Salts and Cannabinoids Analyzed by GC-IR. Available online: (accessed November 18).

This information has been reviewed and adjusted based on material provided by Thermo Fisher Scientific – Chemical Analysis.

For more information on this source, see Thermo Fisher Scientific – Chemical Analysis.

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