Performance metrics based on signal intensity for ion mobility spectrometry – based explosive trace detectors using inkjet printed materials

Abstract

Commercial off-the-shelf (COTS) explosive trace detectors (ETDs) have become an integral part of security practices aimed at protecting the public, transportation, and facilities. Despite their widespread deployment, quality control procedures that can evaluate day-to-day instrument performance or differences among units of the same manufacture are in need for development. In this work, we describe the preparation of test materials (TMs) using inkjet printing that have fixed dosing levels of two explosives; 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and pentaerythritol tetranitrate (PETN). The uncertainty in the mass of dispensed solute is 0.8% (nominal 1 ng RDX and 5 ng or 20 ng PETN depending on ETD). TMs are stable under storage for at least 20 days at temperatures consistent with indoor and outdoor environments, and can be used by field personnel at deployed locations. Inkjet printing is shown to provide the necessary control over the spatial distribution of analyte on the substrate, thus limiting the variability in the signal response due to the sample. Measurements of signal intensities for two COTS ETDs were obtained from TMs over multi-year time spans and for multiple units of each ETD. Reproducibility in the signal response is shown to be between 6% and 15% RSD, or approximately double the within-day variability. The large datasets allow for the first time modeling of signal intensities with respect to normal distributions, which support the use of standard 3-sigma control practices.

In-source collision induced dissociation of inorganic explosives for mass spectrometric signature detection and chemical imaging

“…These explosives have been detected using a range of analytical techniques, including ion chromatography (IC) [1,2], capillary electrophoresis (CE) [3,4], high performance liquid chromatography (HPLC) [5], and most notably, ion mobility spectrometry (IMS) [6][7][8][9][10][11][12][13] and mass spectrometry (MS) [14][15][16][17][18][19][20][21][22]. The rapid analysis times and cost effectiveness of these field compatible instruments have led to widespread deployment of ion mobility spectrometry.…”

Ion mobility spectrometry nuisance alarm threshold analysis for illicit narcotics based on environmental background and a ROC-curve approach

“…In addition, the laboratory instrument’s amplitude adjusted response to the calibrant was measured 25% higher than the deployed instrument and ~18% RSD across both instruments (less than the >30% RSDs for explosives RDX and PETN previously measured across multiple (16) deployed instruments). 21 Though ambient/environmental conditions of the deployed instrument have the potential to introduce variability in the IMS response and even the calibrant response, the calibration correction (Figure S-2) and intensity (Figure S-3 and S-4) for the instrument was monitored and remained relatively stable across the multiyear period of sample collection, showing no systematic drift in response. In addition, previous work comparing the responses of multiple deployed commercial instruments found no correlation between response and environmental conditions (e.g., temperature or humidity).…”

“…In addition, previous work comparing the responses of multiple deployed commercial instruments found no correlation between response and environmental conditions (e.g., temperature or humidity). 21 Finally, previous long-term studies of laboratory and deployed instruments found response variability (relative standard deviation) was derived from the technology limitations and instrument manufacture, as opposed to environmental contamination. 21 …”

“…21 Finally, previous long-term studies of laboratory and deployed instruments found response variability (relative standard deviation) was derived from the technology limitations and instrument manufacture, as opposed to environmental contamination. 21 …”

Flexible SERS-based substrates: challenges and opportunities toward an Army relevant universal sensing platform

“…For bulk detection, ideally materials would be detected and identified prior to use in terrorist activities. Towards this end, traditional bulk detection has been achieved via X-ray based instrumentation 43 , trained animals 45 , ion mobility spectroscopy [46][47][48][49] , terahertz spectroscopy, chemical sensors 50 and optical sensors. Typically at checkpoints, materials (less than bulk quantity) are tested for and collected via swabbing or vapor accumulation techniques.…”