2.2 Preparation of artificial explosive vapor and vapor collection experiment
Each explosive was dissolved in a volatile solvent of acetone, and explosive solutions of 4.17 μg/mL were prepared. Experiments were carried out using a DLH-010 fume hood (410 L) of Jeiotech Co. (Republic of Korea). The dimension of the collection matrix was 5 × 8 cm2. Explosive vapor was artificially produced by spraying the explosive solution. A total of 5, 10, and 20 μg of the explosive were introduced into the hood by spraying 1.2, 2.4, and 4.8 mL of the explosive solution, respectively. These values correspond to the explosive vapor concentrations of 12, 24, and 49 ng/L, respectively, in the hood. The experimental procedure was as follows: (1) two sets of the matrices were arranged at the bottom part of the hood, (2) the explosive solution was sprayed at the top part of the hood, (3) the explosive vapor was collected for 30 sec, and (4) IMS analysis was carried out with the collection matrix. The generation of artificial explosive vapor and the vapor deposition in the collection matrix are described in Figure 1. Aerosols were formed by spraying the explosive solution, which leads to the acceleration of acetone evaporation.
Two arrangement types of the horizontal and vertical positions of the collection matrices were employed as shown in Figures 2 and 3, respectively. The base side area of the hood was 90 × 64 cm2. For the horizontal arrangement, two sets of 15 collection matrices were placed at 12 cm from the wall. For the vertical arrangement, two sets of 15 collection matrices were placed at 14 and 15 cm from the wall. Two sets of collection matrices were located at different sites to avoid positional effects.