RESUMO
A modified approach for characterization of the vapor-time profile of the headspace odors of explosives was developed using solid-phase microextraction (SPME) incorporating introduction of an externally-sampled internal standard (ESIS) followed by gas chromatography/mass spectrometry (GC/MS) analysis. With this new method, reproducibility of the measurements of 2-ethyl-1-hexanol and cyclohexanone were improved compared to previous work (Hoffman et al., 2009; Arthur and Pawliszyn, 1990) through the use of stable-isotope-labeled internal standards. Exposing the SPME fiber to the ESIS after sampling the target analyte proved to be advantageous, while still correcting for fiber variability and detector drift. For the analysis of high volatility compounds, incorporation of the ESIS using the SPME fiber in the retracted position minimized the subsequent competitive loss of the target analyte, allowing for much longer sampling times.
