Discrimination of combustion fuel sources using gas chromatography-planar field asymmetric-waveform ion mobility spectrometry

Smoke plumes from cotton, paper, grass, and cigarettes and emissions from a gasoline engine were sampled using solid-phase microextraction (SPME) and samples were analyzed for volatile organic compounds (VOC) using gas chromatography-mass spectrometry (GC-MS). Chemical compositions were sufficiently distinct to allow source identification. Unfortunately, advanced smoke detectors based on GC-MS would be too slow and expensive for most applications. Direct sampling of smoke by atmospheric pressure chemical ionization-mass spectrometry produced a complex response, demonstrating that VOC in smoke were suitable for gas phase chemical ionization. The complexity also indicated the necessity of chromatographic prefractionation. Planar Field Asymmetric-waveform Ion Mobility Spectrometry (PFAIMS) as a capillary GC detector generated chemical information orthogonal to GC retention times. The combination of SPME preconcentration and the additional information provided by the PFAIMS detector yielded unique patterns from smoke from each fuel. Reconstructed ion chromatograms extracted from the PFAIMS scans indicated sufficient resolution of chemical constituents could be completed in less than five minutes with little loss of analytical information. These first measurements suggest that a GC-PFAIMS instrument operating at ambient pressure in air might result in a compact and convenient fuel specific smoke alarm at a reasonable cost.