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Incapacitating Agents and Technologies: A Review *
Published in Brian J. Lukey, James A. Romano, Salem Harry, Chemical Warfare Agents, 2019
n-Butyl mercaptan is also known as 1-butanethiol. It is a colorless flammable liquid having a strong and obnoxious garlic-like odor. It has a high vapor pressure (83 mm Hg at 388°C; MSDS, 2005a). The odor threshold is 0.1–1 ppb, and it is stated to have a “readily noticeable” odor at concentrations between 0.1 and 1 ppm. The American Conference of Governmental Industrial Hygienists (ACGIH) time-weighted average (TWA)8 threshold limit value (TLV) is 0.5 ppm based on irritation, CNS effects, and reproductive toxicity (ACGIH, 2006). Oral LD50 values (rat) are cited as 1500 and 1800 mg kg−1, and the rat i.p. LD50 is 399 mg kg−1 (Fairchild and Stokinger, 1958; MSDS, 2005a).
Cancer breath testing: a patent review
Published in Expert Opinion on Therapeutic Patents, 2018
K. M. Mohibul Kabir, William A. Donald
Owing in part to the considerable resources required to use MS-based methods at the point-of-care, recent research has focused on the development of portable and inexpensive sensors that can be operated with minimal training. Relatively uncommon analytical approaches that have been used in recent inventions include those based on QCM and optical sensors [79–82]. In QCM, the resonance frequency of a surface electrode in the device decreases when a target analyte lands on the electrode that is usually coated with an analyte-sensitive surface. The major advantage of QCM is that the device is highly portable, easy-to-fabricate, and electrode surfaces can be used that are selective to specific VOCs. Given that different VOC biomarkers can be identified for different types of cancers, an array of QCM sensors with different type of analyte-sensitive layers can potentially be used to diagnose various types of cancers. Such a sensor array concept can also be used in the form of an E-nose in which chemical ensembles are detected by an array of different types of sensors together with a pattern recognition method (Figure 3). In the invention US 9528979 B2 [20], an E-nose sensor was disclosed that had an array of two types of nanosensors: (i) an assembly of metal nanoparticles coated with various organic layers and (ii) single wall carbon nanotubes (SWCNT) coated with a range of polycyclic aromatic hydrocarbons. For the metal nanoparticle-based sensor array, gold nanoparticles were coated with a wide variety of organic ligands using gold-thiol surface chemistry to enable the adsorption of various types of VOCs onto the particles [58]. The particles were deposited on a number of interdigitated electrodes to ensure electrical connections to the different types of nanoparticles. The molecules used for the surface coatings included 2-ethylhexanethiol, 2-amino-4-chlorobenzenethiol, 2-mercaptobenzimidazole, 2-mercaptobenzoazole, 2-nitro-4-trifluoromethylbenzenethiol, 3-methyl-1-butanethiol, 4-methoxy toluenethiol, dodecanethiol, hexanethiol, and tert-dodecanethiol. The specific surface coatings can adsorb different VOCs to different extents. Upon exposure to VOCs, each nanoparticle electrode in the array undergoes a reversible and specific change in resistivity owing to the different surface coatings. The use of multiple sensor platforms allows each analyte to produce distinct fingerprints from the cross-reactive sensors and thus results in the identification of a wider range of chemical species than is possible by use of a single sensor. A similar sensing principle was used for the SWCNT-based sensor array, which was fabricated by forming an electrically continuous SWCNT network that was formed by drop-casting SWCNTs onto a number of interdigitated metal electrodes [83]. Different SWCNT layers were then coated with different polycyclic aromatic hydrocarbons (PAHs). The use of different PAHs allowed the differential adsorption of different VOCs to the individual SWCNT sensors in the array, which changed the electrical properties of the sensor network. Thus, distinct patterns can be obtained for different breath samples.