Measuring and testing – Gas analysis – Odor
Reexamination Certificate
2002-07-25
2004-01-06
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
Odor
C073S863110, C422S083000, C250S288000, C424S094600
Reexamination Certificate
active
06672133
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hand-held chemical vapor detector for detecting biological substances in an indoor and outdoors setting. More specifically, the present invention relates to a plasma chromatograph (PC) vapor detector that is interfaced to a biological sample processing and transfer introduction system. The biological sample processing was accomplished by quartz tube thermal decomposition (TD), and the resultant vapor was transferred by gas chromatography (GC) to the PC detector. This system is comprised of a thermal decomposition module, gas chromatography module and a plasma chromatograph detector. These components are connected in a series fashion. The device is referred to as a Biological Classifier System (BCS). The BCS can be described as a hyphenated device where two analytical dimensions (the GC and PC), in series, allow the separation and isolation of individual components from the thermal decomposition of biological analytes.
2. Brief Description of Related Art
Recent and current events around the world have highlighted the possibilities for deliberate outdoor dissemination of harmful biological substances, and at least 12 countries are known to have some degree of biological warfare program capabilities. Alleged biological terrorism attacks in Japan and threats on U.S. domestic commercial establishments have increased significantly in the past five years. Reports of alleged localized aerosol releases and hoax domestic biological terrorism in the form of postal mail packages, allegedly with spores of the pathogenic
Bacillus anthracis
and
Yersinia pestis
(bubonic plague) organisms, serve to exacerbate the problem.
Desirable goals in effectively countering the biological warfare and terrorism applications of harmful biological agents include their ready detection and possible identification in a relatively short period of time. The detection of biological aerosols, particularly that of bacterial cells and spores, is an important component of U.S. military biological programs. A portion of these programs consists of analytical instrumentation to effect trigger, detection, and identification responses for the presence of bacterial aerosols.
Analytical investigations of aerosols have relied on a diverse set of approaches over the last three decades from experimental determinations of generated aerosols from bulk solutions to real time analyses of ambient outdoor particles. These investigations have included inorganic (salts) and organic particulates as well as bioaerosols that include microorganisms, fungi, and pollen. An accounting of the most prevalent techniques and instrumental methods appears constructive with respect to the present analytical detection method of biological aerosols.
Traditional methods for the characterization of aerosols consist of sampling ambient air and collecting/concentrating them on various matrices (1-3). These biological aerosol particulates are then subjected to sample detection techniques such as polymerase chain reaction (PCR) (1,2,4,5), colony plate count or most probable number (MPN) (1,4,6,7), bioluminescence from inherent adenosine triphosphate (ATP) (4,8), phase-contrast microscopy (4), and immunoassay (1,4,9). The bacterial aerosol samples were characterized by these traditional detection techniques in either an off-line or on-line fashion.
Pseudomonas fluorescens
bacteria were aerosolized and directed to an agar plate with a laser sizing system placed after the aerosol generator. This was an important development in that a relation could be produced between the total number of particles and the number of bacterial-colony-forming units on the agar growth plate (10).
Mass spectrometric methods have had a long and rich history as analytical vehicles for investigating compositional properties of artificial and outdoor man-made aerosols as well as ambient organic and inorganic aerosols under off-line or on-line analysis conditions.
Laser microprobe mass analysis (LAMMA) has been used in an off-line fashion to investigate aerosol particles. Particles were collected or placed on a matrix or wire mesh and were introduced into a vacuum. A microscope guides a laser beam to a selected particle or spot on the matrix surface where ions desorb and are analyzed by a time-of-flight mass spectrometer (TOFMS). Relatively low molecular weight species were usually observed, and known species mostly represented the inorganic salt fraction of samples such as
Mycobacterium leprae
(11,12),
B. anthracis. B. thuringiensis,
and
B. cereus
(13,14) as well as ionized species of particulates including polyaromatic hydrocarbons (PAH) (15) and salt species. Two recent review articles on LAMMA document the principal and extensive applications of TOF and Fourier-transform mass-spectrometer analyzers in the analysis of laser generated ions of single aerosol particles (17,18) that were placed or impacted on matrix supports.
The TOFMS field evolved to where an aerosolized suspension of biological particulates could be introduced into a vacuum as single particles. This procedure, particle analysis by mass spectrometry (PAMS), used either a hot rhenium filament to pyrolyze individual bacterial particles (19-22) or a laser to desorb and ionize species from particles (22,23). These biological particles, including
Pseudomonas putida, Bacillus cereus,
and
Bacillus subtilis
var.
niger
were generated from an ethanol-water suspension. Linear quadrupole mass spectral determinations mainly produced unknown pyrolysis fragments and inorganic salt-derived species.
A similar system, developed by Gieray, Reilly, Yang, Whitten, and Ramsey (24) used an ion trap mass spectrometer detector. From a bulk water suspension, bacterial aerosol particles were sensed and a trigger was provided by the particles passing through two argon ion laser beams. An excimer laser ablated the particle in the ion trap so as to produce ions. An improvement on this basic design was that of a TOF system (25-27) replacing the quadrupole mass spectrometer designs. This allowed for faster mass spectral scanning of ions from particles generated from bulk suspensions or directly from laboratory ambient air. Salt particles as well as tobacco smoke and soot were analyzed.
Hars et al. used a combined electrodynamic balance/ion trap mass spectrometry technique for trapping and stabilizing aerosolized particles of polystyrene and
Bacillus subtilis
spores, followed by laser fragmentation/ionization to obtain mass spectra of the ions generated during a 450-mJ pulse from a Nd-YAG laser. They demonstrated the feasibility to use this technique for chemical and physical characterization of single cells of microorganisms and other components of respirable aerosols (28,29). In other work, an aerosol particle-sizing laser was interfaced to a laser thermal desorption/ionization beam for TOFMS analysis on organic and inorganic compounds (30,31).
Prather et al. published a series of evolving articles with the concept of size, aerodynamic diameter, chemical composition and composition class, and temporal characterization of outdoor aerosol particles (32-39). The centerpiece was a transportable aerosol concentrator, dual time-of-flight mass spectrometer. Positive ions are analyzed in one tube and negative ions, from the same particle, are analyzed in the second time-of-flight tube. As an example, over a period of four days, pyrotechnic explosives (fireworks) particles were monitored in the atmosphere: monitoring sites were 0.5 and 3 miles from the explosion sources (37). Further examples of this technology are the characterization of automobile emissions (36) where metals, oxides, hydroxides, and polyaromatic hydrocarbons (PAH) were detected, and in the temporal monitoring of the nitric acid to hydrochloric acid heterogeneous chemistry that occurs in atmospheric aerosols over the ocean-land mass interface (39).
Gas chromatography (GC)-MS has been used for the trace analysis of bacteria and fungi in organic dust aerosols from environments such as
Maswadeh Waleed M.
Parekh Dhirajlal G.
Snyder A. Peter
Tripathi Ashish
Biffoni Ulysses John
Politzer Jay L
The United States of America as represented by the Secretary of
Williams Hezron
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