Carboxen/PDMS, 85 μm Stable-flex, 24 gauge SPME fibers were used (Sigma-Aldrich, St. Louis, MO, USA). Briefly, experimental conditions were as follows: drugs were placed in separate, pre-cleaned and oven-baked 16 ounce mason jars with modified lids. The Carboxen/PDMS SPME fibers were exposed to the headspace and volatiles were passively extracted; equilibration time was the same as extraction time (1 h at ambient temperature). When the extraction step was completed, the SPME fiber was retracted, wrapped in pre-baked aluminum foil, placed in a pre-cleaned mason jar, and transported back to the laboratory in a cooler on ice. In the laboratory, fibers were stored as described above in a 4 °C refrigerator pending placement into the heated injection port of the MDGC-MS-O for thermal desorption and analysis.

MDGC-MS-O analysis was performed on an Agilent 6890 GC, with a restrictor guard column, non-polar capillary column (BP-5, 56 m × 530 μm inner diameter × 1.00 μm thickness, SGE, Austin, TX, USA) and polar capillary column (BP-20, 25 m × 530 μm inner diameter × 1.00 μm thickness, SGE, Austin, TX, USA) connected in series. Outflow from analytical column was held at 7.0 cc/min. Sample flow was split 3:1 via open split interface to the sniff port and mass spectrometer, respectively, as determined by restrictor column inner diameter. Desorption time was 2 min in splitless mode at 270 °C under flow of helium carrier gas (99.995% purity). Analysis of the same fiber immediately after sample injection, revealed no carry over, with all compounds desorbed in the initial analysis. The oven temperature was programmed as follows: 40 °C for 3.00 min, then increased to 220 °C at a rate of 7.00 °C per min, and held for 11.29 min (40 min total run time). The carrier gas was set at constant pressure at the midpoint (junction point of the non-polar and polar column) at 5.8 psi. Transfer line to the MS was set at 240 °C; transfer line to the sniff port was set at 240 °C with humidified air set at 8.00 psi. MS heated zones were 150 °C for the quadrupole and 230 °C for the source. Mass spectrometer parameters were electron impact (EI), electron energy set to 70 eV, with acquisition range m/z 33–280.

The instrument was tuned daily and analysis of column blanks did not show any contaminating compounds. Analysis of blank trip fiber (an unloaded SPME fiber taken to the site and back, stored with fibers to be analyzed) at the end of each sampling run did not demonstrate contaminating compounds. VOCs were identified tentatively using the Automatic Mass Spectral Deconvolution and Identification System (AMDIS) (National Institute of Standards and Technology, Gaithersburg, MD) and six specialty mass spectral libraries provided derived from the NIST05/EPA/NIH mass spectral database. Known retention times of standards previously analyzed on this system were used for identification. Chemical standards available in house were analyzed to match retention times and mass spectra of unknown compounds. Select reference standards were used for identification, purchased from Sigma-Aldrich (St. Louis, MO, USA). These standards are indicated with ‘+’ in Table 3, Table 4, Table 5. Each sample (as outlined in Section 1.5) was collected on a single SPME fiber, each fiber sample was analyzed by one panelist. The same panelist analyzed all samples with volatiles from each drug and surrogate scent formulation.