1. Forensic drug analysis of chloro-N,N-dimethylcathinone (CDC) and chloroethcathinone (CEC): Identification of 4-CDC and 4-CEC in drug seizures and differentiation from their ring-substituted positional isomers
Wing-Chi Cheng, Wing-Cheong Wong Forensic Sci Int. 2019 May;298:268-277. doi: 10.1016/j.forsciint.2019.03.002. Epub 2019 Mar 9.
We report our findings for the determination of 4-chloro-N,N-dimethylcathinone (4-CDC), a newly encountered NPS in drug seizures examined in our laboratory, and its differentiation from 4-chloroethcathinone (4-CEC), one of the most common cathinones examined locally, and their respective regioisomers, namely 2-CDC and 3-CDC, as well as 2-CEC and 3-CEC in routine drug analysis. As CDCs and CECs have the same molecular mass of 211 with similar and non-characteristic spectra when analysed by gas chromatography-electron ionization-mass spectrometer (GC-EI-MS), it is imperative to establish methods easily amendable for forensic laboratories to differentiate these substances unambiguously. To confirm the identity of the solid, reference standards of all regioisomers of CDC (i.e., 2-CDC, 3-CDC and 4-CDC) and CEC (i.e., 2-CEC, 3-CEC and 4-CEC) were acquired and analysed using GC-EI-MS, liquid chromatography-diode array detector (LC-DAD) and Fourier Transform Infrared Spectrophotometer (FTIR) commonly used in routine forensic drug analysis. In addition, drug analysis with gas chromatography-chemical ionization-mass spectrometer (GC-CI-MS) using methane as the reagent gas operated in positive mode was also explored. It is found that using GC-EI-MS, all isomers of CDCs and CECs eluted with close but different retention times. However, the mass spectra between respective regioisomers were similar and difficult to distinguish. Using LC-DAD, the retention times of all studied cathinones were again different although there were partial overlap between 3-CDC and 4-CDC as well as between 3-CEC and 4-CEC but they all have distinguishable UV spectra. Apart from the detection of quasimolecular ion as the most prominent ion for each cathinone, GC-CI-MS is considered a superior technique to determine all six cathinones where each cathinone showed a unique fragmentation pattern for ease of identification. The analytical techniques have been applied for the examination of drug seizures where 4-CDC and 4-CEC were unambiguously identified either as a single component or mixed components in the seized materials. While FTIR is capable of providing confirmative structural information for the cathinones with each regioisomer exhibits a distinctive pattern but requiring high drug purity, LC-DAD and GC-CI-MS are demonstrated to be useful techniques that can readily differentiate structurally similar synthetic cathinones (even in mixtures) for routine forensic drug analysis.
