Raman spectroscopy has been widely proposed as a technique to nondestructively and noninvasively interrogate the contents of glass and plastic bottles. In this work, Raman spectroscopy is used in a concealed threat scenario where hazardous liquids have been intentionally mixed with common consumer products to mask its appearance or spectra. The hazardous liquids under consideration included the chemical warfare agent (CWA) simulant triethyl phosphate (TEP), hydrogen peroxide, and acetone as representative of toxic industrial compounds (TICs). Fiber optic coupled Raman spectroscopy (FOCRS) and partial least squares (PLS) algorithm analysis were used to quantify hydrogen peroxide in whiskey, acetone in perfume, and TEP in colored beverages. Spectral data was used to evaluate if the hazardous liquids can be successfully concealed in consumer products. Results demonstrated that FOC-RS systems were able to discriminate between nonhazardous consumer products and mixtures with hazardous materials at concentrations lower than 5%. 1. Introduction In August 2006, a terrorist plot to destroy aircrafts on transatlantic flights was discovered and timely stopped in London. The plan involved the use of liquid explosives stored in beverage bottles that would pass checkpoints without being detected [1]. The liquids were going to be mixed in flight to create an improvised explosive device (IED) that was going to be left in the aircraft and detonated remotely after the aircraft landed. Immediately after the event, airport security agencies in the United Kingdom and the United States of America established a ban on all liquids except medicines and infant food beyond checkpoints. The position of airport security officials has changed several times to allow certain amount of liquid or gel-based products. However, when or how terrorists would try to pass hazardous liquids into ports, government buildings, or public areas to generate threats using explosives or chemical agents is unpredictable. The possibility of using liquid explosives for terrorism purposes is accompanied by the use of chemical warfare agents (CWAs) or toxic industrial compounds (TICs) for the same purposes. Such chemicals, which can be accessed in large quantities, can be extremely toxic on contact or inhalation even at small quantities [2, 3]. The establishment of current regulations also recognizes the challenges of detecting dangerous liquids when hidden or mixed within common nondangerous products. For this reason, it is important to develop methodologies that would enable to differentiate between
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