Because identification of fentanyl analogues pose a challenge to laboratories in identifying them, the current study developed a novel analytical technique in which gas chromatography (GC) is interfaced with both cold electron ionization mass spectrometric (cold EI MS) and vacuum ultraviolet (VUV) detection by the means of a flow splitter for the simultaneous qualitative and quantitative analysis of 24 fentanyl analogues, including seven sets of positional isomers.
Fentanyl and its derivatives are amongst the ever-growing list of emerging drugs which are impinging on current traditional analytical techniques used in forensic laboratories. To avoid current regulations, fentanyl analogues are being illicitly synthesized by slight alterations of functional groups to the fentanyl skeleton, leading to inaccurate identifications and posing the greatest challenge to laboratories. For most of the 24 analogues in the current study, enhanced molecular ions were obtained with at least 1 percent intensity relative to base peak. In addition to enhanced molecular ions, the GC-cold EI MS maintained fragmentation pathways observed by GCMS with classical electron ionization. For the most part, VUV detection resulted in unique VUV spectra for fentanyl analogues including positional isomers. The combination of these two complementary detectors in tandem with the high resolving power of the gas chromatograph, enables higher confidence in analyte identification by the combination of retention times, cold EI mass spectra and VUV spectra. The preferred method for quantitation was based on VUV detection and offered excellent determination coefficients (R2 0.999) for most analytes over two orders of magnitude dynamic range, without the need for deuterated internal standards. For both run-to-run and day-to-day repeatability studies, at moderate solute concentrations, the correct fentanyl related compound was identified in almost every instance from a library containing all the fentanyl analogues plus hundreds of other analytes. (publisher abstract modified)