Radiometrically characterised ultraviolet light-emitting diode (UVLED) based micro-photoreactors for rapid, safe and portable screening of organic peroxide explosives

Abstract

Background: Screening organic peroxide explosives (OPEs) such as hexamethylene triperoxide diamine (HMTD), methyl ethyl ketone peroxide (MEKP), and triacetone triperoxide (TATP) from ambient interferents (e.g. household H₂O₂, perfume, and nail polish remover) at the security heightened areas has been a significant challenge for the security authorities worldwide. The present research aims to overcome this challenge for the first time by integrating a UV LED based micro-photoreactor with an in-house developed stabilising reagent to screen the OPEs from household H₂O₂.

Results: Since OPEs along with H₂O₂ upon their exposure to UV radiation spontaneously generate peroxy moieties and radicals, the aqueous stabilising reagent, composed of dimethyl sulfoxide (100 mM), sodium thiosulfate (100 μM), and cobalt chloride (10 μM), was developed to effectively stabilise these peroxy moieties. We confirmed this stabilising phenomenon by investigating GC-MS profile of OPE samples with/without activating the micro-photoreactor, revealing controlled stabilisation of photodegradation products from MEKP and significant stabilisation of those from HMTD and TATP. Notably, we observed how the swabs of OPEs from skin surfaces, when immersed in the screening reagent prior to their transfer via the active micro-photoreactor (driven with radiometrically optimised parameters e.g., 800 KHz, 3.3 V, and 0.13 Amp), enabled flow injection analysis-chemiluminescence (FIA-CL) signals remarkably distinguishable from that of H₂O₂ within 10 s.

Significance and novelty: We present a novel screening mechanism of OPEs from household products using in-house developed and radiometrically characterised UVLED based portable micro-photoreactors as well as stabilising reagent to stabilise the photodegradation of OPEs. This study affords selective and ultra-trace level of screening of HMTD (0.12 μM, n = 3, RSD 6 %), MEKP (0.08 μM, n = 3, RSD 6 %) and TATP (0.16 μM, n = 3, RSD 7 %) from H₂O₂, highlighting its potential for real-world explosive screening applications in security heightened settings in a rapid, safe, and effective manner.

Keywords: FIA-CL; H(2)O(2); Micro-photoreactor; Organic peroxide explosives; Screening; Stabiliser; UV LED.