Detecting Trace Amounts of Peroxides and Ammonium Nitrate in Fingerprints by Ion Mobility Spectrometry

The effect of the sweat and grease deposits (SGD) from fingerprints on the detection efficiency of trace amounts of explosive substances—triacetone triperoxide (TATP), hexamethylene triperoxide diamine (HMTD), and ammonium nitrate (AN) by ion mobility spectrometry in air at atmospheric pressure was investigated. Among the main components of SGD, urea is identified as a positive mode influencer, while lactic acid (LA) affects in a negative mode. The presence of urea or SGD in the sample does not significantly affect the detection of TATP in the positive mode but decreases the efficiency of HMTD ion formation and leads to the appearance of adduct cations of HMTD and urea. The presence of lactic acid or SGD slightly decreases the efficiency of ammonium nitrate ion formation in the negative mode and significantly alters the qualitative composition of HMTD ions, leading to the appearance of HMTD and LA adduct anions. In the absence of any impurities in the sample, the best reduced limit of detection (signal-to-noise ratio = 3σ), estimated at 30–50 pg, was observed for HMTD. The lifetime of HMTD, TATP, and AN traces on aluminum foil under laboratory conditions was determined to be 1, 3, and 12 h for samples with masses of m_HMTD 1 × 10^–9, 2 × 10^–9, and 1 × 10^–8 g and surface densities d_s of 0.008, 0.016, and 0.08 μg/cm², respectively; 10² and 10³ s for m_TATP 1 × 10^–5 and 1 × 10^–4 g and d_s of 80 and 800 μg/cm², respectively; 12 and 25 h for m_AN 3 × 10^–8 and 5 × 10^–8 g and d_s of 0.24 and 0.4 μg/cm², respectively.