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Fentanyl analogues and their positional isomers have similar chemical structural configurations making them difficult to identify and differentiate. Gas chromatography coupled to a gas-phase infrared detector (GC-IRD) is a useful and powerful tool for the unambiguous identification of fentanyl compounds where traditional analytical techniques such as gas chromatography–mass spectrometry (GC–MS) offer limited information for this class of compounds. In this study, we demonstrate the utility of GC-IRD and show how this complementary information enables the identification of fentanyl analogues (2- and 3- furanylfentanyl, 2-furanylbenzylfentanyl, croto- nylfentanyl, cyclopropylfentanyl, methoxyacetylfentanyl, carfentanil, meta-fluoroisobutyryl fentanyl, para- fluoroisobutyryl fentanyl and ortho-fluoroisobutyryl fentanyl) when combined with GC–MS data. A description of the operating conditions including how the optimization of GC-IRD parameters can enhance the spectral resolution and unambiguous identification of these fentanyl analogues is presented, for the first time. In par- ticular, the effects of light pipe temperatures, acquisition resolution, the use of a programmed temperature vaporizing (PTV) inlet, and the analytical concentration of the sample were evaluated. A real-world case ex- ncountered in casework and how the implementation of GC- of these challenges in fentanyl differentiation and identification. 

A novel extraction device, capillary microextraction of volatiles (CMV) was coupled to a TRIDION-9 GC–MS with a needle trap (NTD) and evaluated for the analysis of ignitable liquids fire debris. The performance of the TRIDION-9 was compared to a benchtop GC–MS using CMV. A system detection limit of ~10 ng for each of 20 key ignitable liquid residue (ILR) compounds was determined for the T9 GC–MS. Dynamic headspace sampling of simulated ILRs was performed in closed and open-air systems. Closed system evaluations the CMV/NTD technique resulted in extraction performance similar to the CMV alone; however, ILR analysis on the T9 was impacted by limited chromatographic resolution. Compound identification was possible for 14 out of the 20 selected compounds on the T9 when 1 μL of a 1% standard accelerant mixture (SAM) was sampled, compared to 17 compounds on the benchtop GC–MS for the same mass loading. Open-air sampling with a modified vapor source resulted in the retention of most compounds with as low as 5 min. sampling, and equilibrium concentrations were reached after 10 min. No significant differences were observed between CMV and CMV/NTD sampling suggesting that the combined technique does not suffer from affinity bias. While the potential of the CMV/NTD extraction coupled to a T9 GC–MS for fire debris analysis was limited by the chromatographic resolution of the instrument, this study serves as proof of concept for the CMV’s potential for the extraction of ILRs in combination with portable GC–MS systems.