Analysis of substituted Cathinones and fentanyl analogs by gas chromatography-infrared spectroscopy (GC-IRD) using nitrogen carrier gas

Substituted cathinones and fentanyl analogs that are positional isomers can produce similar mass spectra and retention times, which poses challenges for their identification. A gas chromatography-infrared spectroscopy (GC-IRD) method, developed using nitrogen as the carrier gas, was employed as a complimentary technique to gas chromatography-mass spectroscopy (GC–MS) for the accurate identification of positional isomers. Due to the global helium shortage and since Agilent helium (nitrogen switch) conservation modules were currently in use, nitrogen was selected and a novel method was developed for the analysis of controlled substances. A total method run time of 26 min for the analysis of 29 certified reference materials comprised of substituted cathinones and fentanyl analogs was achieved. A drug mixture was also analyzed to evaluate the resolution and retention time. Standards were prepared at concentrations of 100 μg/mL, 1 mg/mL and 2 mg/mL and analyzed over a 3-day period, where the 2 mg/mL concentrations of the standards were run in triplicate on day 1 and once on days 2 and 3. Twenty-seven of the standards were identified with a library match of 0.98 or higher for the 1 mg/mL concentration. Each standard experienced a retention time (RT) coefficient of variation (%CV) less than 3 %. For the drug mixture peak resolution exceeded 1.5 for each component. The GC-IRD validated method was found to be a suitable complementary analysis technique to GC–MS for analyzing substituted cathinones and fentanyl analogs, as demonstrated by the repeatable and reproducible RTs and library matches obtained during method validation.