Characterization of fentanyl HCl powder prior to and after systematic degradation

Fentanyl HCl is of particular interest in forensic cases but there is a notable gap in literature regarding its analysis. This study utilized a multi-method approach to characterize fentanyl HCl powder, both fresh and following a forced degradation process. Using sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) and direct injection gas chromatography–mass spectrometry (GC–MS), five compounds were identified in fresh fentanyl HCl powder. The identified compounds were: N-phenylpropanamide, 1-phenethyl-4-propionyloxypiperidine (1-P-4-POP), 4-anilino-N-phenethylpiperidine (4-ANPP), acetylfentanyl, and fentanyl; all identified compounds but acetylfentanyl and fentanyl decreased in quantity as the sample was degraded. Fresh headspace samples analyzed with solid phase microextraction (SPME)-GC–MS identified four compounds in common with the powder analyses: N-phenylpropanamide,1-P-4-POP, 4-ANPP, and fentanyl. Acetylfentanyl was not present in the headspace samples, although two additional compounds were: N-phenylacetamide and N-phenethyl-4-piperidinone (NPP). Where direct analysis of degraded fentanyl HCl showed decreased quantities of the identified compounds, headspace samples of the degraded fentanyl HCl resulted in higher quantities, implying that the degradation process drove those compounds to volatilize. Notably, fentanyl was identified in the headspace, implying that this could be an appropriate target for standoff detection. Finally, thermogravimetric analysis (TGA) and differential scanning calorimetry (DCS) confirmed that the forced degradation process had little permanent effect on the powder.