Ambient ionisation mass spectrometry for the trace detection of explosives using a portable mass spectrometer

Five different classes of explosives were analysed by ambient ionisation mass spectrometry testing selectivity, sensitivity, and repeatability. We compare the effectiveness of two techniques (ASAP and SESI) for the trace detection of five explosives representative of the most common classes of high explosive: HMTD, RDX, PETN, Tetryl and TNT. Experiments also compared the effectiveness of sample loading via a glass fibre swab or glass rod. All analyses were carried out with a Waters Acquity QDa mass spectrometer, a small format mass spectrometer which can be operated in a transportable mode (using ambient air and a small diaphragm pump). Both ambient ionisation techniques, ASAP and SESI, successfully detected the five different explosives which could make them suitable for a screening method. By directly comparing a calibration range of 0.8–10 ng on both swabs and rods for each explosive, it appears that SESI produces less variability per repeat, particularly at the higher end of the range when compared to ASAP which typically has a lower limit of detection and better linearity.