Ionic liquids as stationary phases for the gas chromatographic separation of fentanyl analogues

The continuous emergence of novel fentanyl analogues has created a need for improved methods able to distinguish between fentanyl analogues and their isomers. In this study, the utility of commercially available ionic liquid columns is demonstrated for GC-FID and GC–MS separation and unambiguous identification of fentanyl, 22 fentanyl analogues and U-47700. The selectivity of the IL column towards these compounds was determined as well as the effectiveness of detection from complex illicitly synthesized drug samples. The results of this study were compared to a 5% diphenyl/95% dimethylpolysiloxane column to show increased selectivity and applicability towards seized illicit drug samples. 24 compounds were separated 36% faster with an elution window increase of 33% on the ionic liquid phase compared to the 5% diphenyl/95% dimethylpolysiloxane phase. The selectivity of 11 isomeric analogue sets (out of 12) increased by 2 to 25% over the 5% diphenyl/95% dimethylpolysiloxane phase showing an ionic liquid column is more favorable for separating fentanyl analogues. The ionic liquid column provides better signal to noise, and a faster and more selective option for forensic laboratories looking to identify confiscated illicit drug samples.