Chapter 4 - Colorimetric Detection of Explosives

• Published in: Aspects of Explosives Detection pp. 41 - 58
• Main Authors: Almog, J., Zitrin, S.
• Format: Book Chapter
• Language: English
• Published: Elsevier B.V 2009
• ISBN: 9780123745330; 9780444549365; 0444549366; 9780080923147; 0123745330; 0080923143
• DOI: 10.1016/B978-0-12-374533-0.00004-0

This chapter focuses on color reactions that are extensively used in the field of explosives analysis. Their application is easy, the equipment required is simple and inexpensive, their sensitivities are often in the sub-microgram range, and they enable rapid, on-site diagnostic detection of explosive materials. They are also used for preliminary laboratory tests of materials suspected of being explosive and can help in diagnosing impurities and degradation products of explosives. The main drawback of the use of color reactions for the analysis of explosives lies in their low specificity. Polynitroaromatic compounds were reported to undergo color reactions with numerous bases, such as ammonia in methanol and aqueous solution of tetramethyl-ammonium hydroxide. A completely different approach involves the reduction of a nitroaromatic compound to the corresponding aromatic amine in which Zn, SnCl2, and TiCl3 in acidic medium were used as reducing agents. The most important color reaction for nitrate esters and nitramines is based on the formation of nitrite ions (NO2), upon reaction of these compounds with alkalis, which are then detected by the classical Griess reaction. In 1999, Keinan and Itzhaky registered a patent on peroxide explosive tester, which enabled rapid on-site detection of triacetonetriperoxide (TATP). In the presence of organic peroxides, the outcome is a green-blue color and the detection limit is in the sub-microgram level. A simple, fast, and specific color test for urea nitrate was reported recently by Almog et al., which is based on the reaction between urea nitrate and ethanolic solution of p-dimethylaminocinnamaldehyde (p-DMAC) under neutral conditions from a red pigment that is formed within 1 min from contact.