Simultaneous colorimetric detection of improvised explosive compounds using microfluidic paper-based analytical devices (μPADs)

In this paper the development of microfluidic paper-based analytical devices (mu PADs) is described for rapid, on-site detection of improvised explosives. Five lane mPADs were designed and printed using wax ink on chromatography paper to create hydrophobic channels. Each channel contains colorimetric reagents capable of reacting with one or more explosive compounds resulting in a specific colorimetric reaction. Two devices were prepared, each capable of performing five simultaneous analyses on a single mu PAD. The first mu PAD was developed to detect inorganic explosives such as black powder, flash powder, and ammonium nitrate. It detects nitrate, nitrite, chlorate, and perchlorate oxidizers, as well as ammonium. The second mu PAD was developed to detect military explosives such as TNT and RDX along with other high explosives like urea nitrate. It also detects organic peroxides such as TATP and its precursor hydrogen peroxide. All experiments were performed by dissolving the explosives in deionized water or 50 : 50 acetone/H2O as transport solvents with a detection time of around 5 minutes. Detection limits ranged from 0.39-19.8 mu g of explosive compound. These two customized mu PAD devices permit the on-site forensic testing of unknown explosives, thereby supplying law enforcement and military personnel with a resource for fast, easy detection of military, commercial, and homemade explosive components at low cost.