Chemical detectors, development

Engineers-Architects, 68 Chemical Research Development and Engineering Center, 212 Department of Army, 234 Detector Electronics Corporation, 183 Hazards Research Corporation, 269 Morton Thiokol, 286... 

The detection of a test gas using mass spectrometers is far and away the most sensitive leak detection method and the one most widely used in industry. The MS leak detectors developed for this purpose make possible quantitative measurement of leak rates in a range extending aaoss many powers of ten (see Section 5.2) whereby the lower limit = 10 mbar l/s, thus making it possible to demonstrate the inherent gas permeability of solids where helium is used as the test gas. It is actually possible in principle to detect all gases using mass spectrometry. Of all the available options, the use of helium as a tracer gas has proved to be especially practical. The detection of helium using the mass spectrometer is absolutely ( ) unequivocal. Helium is chemically inert, non-explosive, non-toxic, is present in normal air in a concentration of only 5 ppm and is quite economical. Two types of mass spectrometer are used in commercially available MSLD s ... 

On the defensive side, service requirements were promulgated for a real-time detector for nerve agents in the field, shipboard detectors for Royal Navy vessels, prophylactics and therapy for nerve agent poisoning and a new respirator. The procurement cycle for some of these items was relatively quick, but for others, in particular the respirator, the process was one of continuous improvement reflecting advances in science and technology. However, to try to provide a succinct analysis of the first 20 post-war years of chemical weapon development in Britain is difficult mainly because many topics cannot be reported due to the non-disclosure of sensitive documents by the British government. 

Another promising avenue for research that Is unquestionably at the frontier of science concerns development of an understanding of processes Involved In olfactory perception. We know from our research on the sex pheromones that male moths possess a phenomenal ability to perceive and respond behavlorally to Incredibly minute quantities of pheromonal compounds In the air. The chemoreceptive sensitivity of this detector system Is certainly unrivaled by any organic-chemical detector system devised by man. 

Chemical Detectors.—It is recognized that some men have a much more highly developed siense of smell than others and are hence able to detect in low couccntration.s that others fsul to perceive at all. To eliminate the hviman equation in detection of the presence of gas, considerable effort has been made, both during the World War and since, to devise... 

Civilian specialized teams that are prepared for working in chemically contaminated focal points are usually provided with different types of chemical detectors and monitoring kits, which are only capable to point to the presence or absence of the suspected chemical substance or a class of chemical. The most-used detectors are designed for detection of organophosphate pesticides, chlorine and cyanide, but the detectors against classical CW agents are usually not available to civilian chemists. Because, currently, the anti-terrorist activities have spiralled upwards, much of todays s military technology has been developed into commercially available equipment, however, the cost of detection equipment items... 

Current R D in chemical agent detector technology is focused on increasing the speed and sensitivity of the instruments, while at the same time bringing down their size and cost. The vast majority of next-generation chemical detectors are based on the application of technology previously discussed. In some cases, the improvement will often be utilization of multiple technologies to simultaneously increase the sensitivity and specificity of the instrument. New CWA detector platforms with near-term successful development prospects include ... 

There are 100 entries in the chemical detector inventory. Twenty-eight percent of the entries are funded by the Department of Defense and 56% by commercial companies. Other funders include DoE, EPA, NASA, and TSWG. Chemical detection devices are much more developed than their biological counterparts 60% of the items in the inventory are commercially available, with only 13% still in the field testing stage and 16% in the laboratory. It is also worth noting that there are three commercial devices that are designed specifically for a civilian market. 

Yes indeed, and we make brief mention of these. We must ask, however, the following question. What other chemical elements are incorporated into organic molecules that are of interest to TEQA Priority pollutant organic compounds of environmental interest that incorporate the elements nitrogen, phosphorus, and sulfur answer this question. GC detectors developed for these elements are of a more recent vintage and include thermionic, flame photometric, and chemiluminescence. In addition, the atomic emission spectroscopic detector (AES) has been recently developed commercially for organometallics. The AES can be tuned to a specific emission wavelength for a particular metal. Development of C-GC-AES techniques have advanced the analytical chemistry of trace metal speciation. 

An alternative method for sniffing a gas sample into an IMS was developed by Smiths Detection for the lightweight chemical detector (LCD). In this approach, the gas sample is drawn through a plenum with a small fan. A pinhole in the plenum... 

Heterogeneous or complex polymers are distributed in more than one molecular parameter. For functional homopolymers one has to deal Avith the overlapping effects of molar mass distribution and functionality type distribution, whereas copolymers are distributed at least in molar mass and chemical composition. For many years, detector development and the use of several detectors attached to SEC have been the major thrusts in chromatographic analysis of complex macromolecules. In particular, the combination of a refractive index and an ultraviolet detector has been used extensively, although only a limited number of polymers is UV active. Therefore the application of this technique is certainly not universal. On the other hand, SEC has its merits in the daily routine because it is simple, fast, and very reproducible. 

The Lightweight Chemical Detector, or LCD series (Figure 6.7), because it was developed more recently, differs slightly from the aforementioned detectors. The LCD uses the open-cell technique that does not contain a radioactive source, and... 

We hope this book will serve as a useful reference to those in the field of developing chemical detectors. Device testing is a vital process toward successful development. It is also hoped that this book will provide the general public with an overview of chemical warfare agents. 

M9 Chemical Detector Kit. Developed at Edgewood Arsenal in 1 44, the Afp kit was one of several devices used to determine presence and type of toxic chemicals. 

Conducting polymer-modified electrodes have potential usage in the fabrication of chemical detector for analytical applications [8]. As many of such research activities have focused extensively on the application of polypyrrole and its derivatives in the fabrication of biosensor especially glucose sensors [9], we have worked on the development of analytical probes using polythiophenes and polybithiophenes. An amperometric glucose sensors fabricated using enzyme/polybithiophene modified electrode has recently been reported [10]. 

Another approach to mass analysis is based on stable ion trajectories in quadnipole fields. The two most prominent members of this family of mass spectrometers are the quadnipole mass filter and the quadnipole ion trap. Quadnipole mass filters are one of the most connnon mass spectrometers, being extensively used as detectors in analytical instnunents, especially gas clnomatographs. The quadnipole ion trap (which also goes by the name quadnipole ion store, QUISTOR , Paul trap, or just ion trap) is fairly new to the physical chemistry laboratory. Its early development was due to its use as an inexpensive alternative to tandem magnetic sector and quadnipole filter instnunents for analytical analysis. It has, however, staned to be used more in die chemical physics and physical chemistry domains, and so it will be described in some detail in this section. 

---