Exactly, 2 μL solution of the relevant explosive was deposited on a microscopic glass slide and allowed to air dry. The sample spot had a diameter of around 2 mm. The solid compounds were vaporized by heating from the backside of the sample spot with an air heater (varying from 150 to 225 °C) linked to a quartz nozzle (i.d. 2 mm). The temperature of the heater was measured using a thermocouple. The solid explosives were gasified with hot air except for TATP, benzene, deuterated benzene, and toluene. These analytes were kept in a separate glass vial as a headspace because to their high vapor pressures at room temperature, and then fed into the ion source through inlet-1 for ionization (Fig. ).