Patent Publication Number: US-8114200-B2

Title: Multi-dimensional portable gas chromatograph system

Description:
CROSS-REFERENCE TO RELATED U.S. APPLICATIONS 
     This application is a Continuation of and claims priority to U.S. patent application Ser. No. 11/435375, filed May 16, 2006, the entire contents of which are hereby incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable 
     FIELD OF THE INVENTION 
     The present invention relates to the field of identification of chemical compounds, and to apparatuses and methods for doing the same. More particularly, the present invention relates to the field of gas chromatography, and to apparatuses therefore. 
     BACKGROUND OF THE INVENTION 
     Gas chromatography (GC) is one of the valuable techniques of analytical chemistry for analysis of complex samples for both environmental and medical applications. 
     As a practical matter, a gas chromatograph is an analytical instrument that separates a gaseous sample, or a liquid sample which has been converted to a gaseous state, into individual compounds so that these individual compounds can be readily identified and quantified. A typical gas chromatograph includes an injector, an analytical separation column, a detector, and an output for displaying the results of the analysis. 
     The injector functions to convert samples to a gaseous state if needed, and moves the gaseous sample to the head of the analytical separation column in a narrow band. The separation column is typically a long coiled tube or the like, that separates the sample into its individual components. Separation columns typically contain liquid or solid materials as a stationary phase, and separate the individual components based on their affinity for the medium, i.e. polar compounds have an affinity for a polar medium and non-polar compounds have an affinity for a non-polar medium, and their molecular weights as they are swept through the column with a carrier gas. Typically, the larger the molecule, the longer it is immobilized within the solid or liquid material within the column, and the longer it is retained within the column. 
     The detector then detects and measures the constituent components as they emerge from the analytical column. Different sample components are retained for different lengths of time within the column, and arrive at the detector at characteristic times. These “retention times” are used to identify the particular sample components, and are a function of the type and amount of sorbtive material in the column, the column length and diameter, the carrier gas type and flow rate, and of the column temperature. Temperature control is a factor in obtaining repeatable data. 
     The output displays the results of the analysis to the user. 
     Gas chromatography is one of the most widely used and accurate methods for chemical identification. However, typical gas chromatographs which are employed in the laboratory are dimensionally large, heavy and not easily transported for use in the field. 
     In recent years, the interest in having portable, lightweight gas chromatographs capable of accurately detecting low and mid-levels of chemical agents has increased significantly. For example, there is a high interest in the use of such detectors to detect chemicals which may be used in warfare or for terroristic activities. 
     There remains a need in the art for an improved, lightweight, portable gas chromatograph which can accurately detect and transmit to a user, low to mid-level concentrations of chemical and/or biological agents. 
     In some embodiments, a gas chromatograph may use a thermal conductivity detector to detect and measure the constituent components of the gasses being analyzed. Thermal conductivity detectors utilizing thermistors are generally known in the art. Such thermistors are generally extremely small and fragile, and therefore the use of thermal conductivity detectors has typically been limited to fixed instruments that are kept in a very stable laboratory environment. There remains a need for a rugged thermal conductivity detector capable of withstanding the vibrations and temperature variations associated with use in the field. 
     The art referred to and/or described above is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. §1.56(a) exists. 
     All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety. 
     Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below. 
     A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims. 
     SUMMARY OF THE INVENTION 
     The present invention relates to portable, multi-dimensional gas chromatographs (GCs). 
     In one embodiment, the present invention relates to portable, multi-dimensional gas chromatographs having at least two separation columns, at least one detector for each of said at least two separation columns, at least one pre-concentrator; and at least one reference chemical. 
     In one embodiment, at least one of the two separation columns is part of a gas chromatograph column assembly (GCCA), the GCCA including a first housing, the first housing defining a first chamber. The GCCA further including a column support, wherein the column support is ring-shaped about an axis and includes a circumferential outer surface oriented about the axis and a plurality of axially oriented bridges, the bridges extending radially from the outer surface of the column support, and wherein the column support is positioned within the first chamber. Column tubing is then wound around the column support, wherein the column tubing is in contact with the plurality of bridges and is separated from the outer surface of the column support. Suitably, the GC includes at least two GCCAs, each GCCA including a separation column. 
     Each detector may be selected from any of a variety of suitable detectors. In one embodiment, at least one of the detectors is a thermal conductivity detector (TCD) having high sensitivity and capability of measuring chemical compounds at very minute concentrations, and suitably at least two of the detectors are TCDs. 
     In one embodiment, at least one of the separation columns includes a stationary phase which is polydimethylsiloxane. 
     In one embodiment, at least one of the separation columns includes a stationary phase which is polyethylene glycol. 
     In one embodiment, the pre-concentrator includes a graphitized carbon-based molecular sieve. 
     In one embodiment, the reference chemical is 1,4-dichlorobenzene. 
     The GC according to the invention, in various embodiments further includes a gas flow regulator for providing gas to the system at a consistent gas flow rate regardless of the pressure at which the gas is supplied. 
     At least one embodiment of the inventive gas regulator is directed towards a two stage gas regulator. The gas regulator has a gas flow path which receives gas from a gas source and outputs it at a reduced pressure. Each stage uses a piston assembly to reduce the pressure of the gas from an entering pressure to an exiting pressure. The gas flow path as a whole has three pressure levels, an input pressure, an intermediate pressure, and an output pressure. The input pressure is caused by the gas source (usually thousands of psi) which enters the first stage. The intermediate pressure (usually hundreds of psi) then exits the first stage and enters the second stage. The output pressure equal to the desired level (usually tens of psi) exits the second stage. The stages are oriented parallel to each other with their respective inputs and outputs facing in opposite directions. Diagnostic devices and manual shutoff assemblies further assist in operating the regulator. The regulator is compact and can be assembled out of common commercially available part. 
     The GC according to the invention in various embodiments includes at least one flow controller. 
     The GC according to the invention in various embodiments further includes at least one multiport valve having first and second positions for loading, analyzing and cleaning of the unit. 
     The GC according to the invention further includes a signal processing unit (SPU) in communication with the detectors. In various embodiments, the SPU further includes analog processing electronics in communication with the detectors which are further in communication with digital processing equipment. 
     The SPU further includes a CPU having a recognition library. 
     In at least one embodiment, a thermal conductivity detector comprises a housing having an internal gas analysis chamber, a fluid inlet passageway in communication with the gas analysis chamber, a fluid outlet passageway in communication with the gas analysis chamber, and a first bore extending through at least a portion of the housing. The first bore is in fluid communication with the gas analysis chamber, and is offset from the fluid inlet and outlet passageways. The thermal conductivity detector further comprises a thermisor having an electrical lead and a first contact pin electrically connected to the electrical lead. The first contact pin is oriented within the first bore, is electrically insulated from the housing and mechanically secured to the housing. 
     These and other aspects, embodiments and advantages of the present invention will become immediately apparent to those of ordinary skill in the art upon review of the Detailed Description and Claims to follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simple block flow diagram of an embodiment of the gas chromatograph according to the invention. 
         FIG. 2  is an enhanced block flow diagram of an embodiment of the gas chromatograph according to the invention. 
         FIG. 3  is a pneumatic block diagram of an embodiment of the gas chromatograph according to the invention. 
         FIG. 4  is a schematic diagram of an embodiment of a multiport valve in combination with a gas chromatograph according to the invention shown in a first position. 
         FIG. 5  is a schematic diagram of an embodiment of a multiport valve in combination with a gas chromatograph according to the invention shown in a second position. 
         FIG. 6  illustrates a specific embodiment of a multiport valve. 
         FIG. 7  is a side schematic of an embodiment of a compact gas chromatograph according to the invention. 
         FIG. 8  is an end view of a gas chromatograph according to the invention with interior parts exposed. 
         FIG. 9  shows a block diagram schematic of the electrical portion of the portable gas chromatograph system. 
         FIG. 10  shows a block diagram of the digital circuitry of the digital board. 
         FIG. 11A  is an electrical circuit schematic showing the TCD bridge analog to digital circuit. 
         FIG. 12  shows a system firmware context diagram. 
         FIG. 13  is a gas chromatograph with interior parts visible. 
         FIG. 14  is a perspective view of an embodiment of a Gas Chromatograph Column Assembly (GCCA). 
         FIG. 15  is a perspective view of an embodiment of a GCCA. 
         FIG. 16  is a perspective view of an embodiment of a GCCA with a portion being transparent. 
         FIG. 17  is a blow-up view of an embodiment of a GCCA. 
         FIG. 18  is a blow-up view of an embodiment of a GCCA. 
         FIG. 19  is a side vies of an embodiment of a column support. 
         FIG. 20  is cross-sectional view along lines  19 A- 19 A of  FIG. 19 . 
         FIG. 21  is a partial cross-sectional view along lines  19 A- 19 A of  FIG. 19 . 
         FIG. 22  is a partial cross-sectional view along lines  19 B- 19 B of  FIG. 19 . 
         FIG. 23  is a partial cut-away perspective view of an embodiment of a GCCA. 
         FIG. 24  is a partial cut-away perspective view of an embodiment of a GCCA. 
         FIG. 25  is a partial cut-away side view of an embodiment of a GCCA. 
         FIG. 26  is a cross-sectional perspective view of an embodiment of a capillary column. 
         FIG. 27  shows an exploded view of an embodiment of a thermal conductivity detector. 
         FIG. 28  shows an embodiment of a sensor housing portion of a thermal conductivity detector. 
         FIG. 29  shows embodiments of a body housing and a sensor housing for a thermal conductivity detector. 
         FIG. 30  shows an embodiment of an end plate and other components of a thermal conductivity detector. 
         FIG. 31  shows an embodiment of an assembled thermal conductivity detector. 
         FIG. 32  shows a sectional view of an embodiment of a thermal conductivity detector, for example as taken across line  32 - 32  of  FIG. 31 . 
         FIG. 33  is a partially transparent perspective view of a Very Small High Pressure Regulator. 
         FIG. 34  is a highly transparent perspective view of a Very Small High Pressure Regulator. 
         FIG. 35  is an exploded perspective view of a Very Small High Pressure Regulator. 
         FIG. 36  is perspective view of a center block seen from the inlet side. 
         FIG. 37  is perspective view of a center block seen from the transfer side. 
         FIG. 38  is lateral view of the center block seen from the transfer side. 
         FIG. 39  is lateral side view of the center block. 
         FIG. 40  is lateral view of the center block seen from the inlet side. 
         FIG. 41  is an overhead cut-away view of the center block. 
         FIG. 42  is an overhead cut-away view of a portion of the center block. 
         FIG. 43  is a photograph of an embodiment of a portable gas chromatograph according to the invention. 
         FIG. 44  is a photograph showing a side panel in the system for accessing the regulator shut-off valve. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While this invention may be embodied in many forms, there are described in detail herein specific embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. 
     For the purposes of this disclosure, like reference numerals in the figures shall refer to like features unless otherwise indicated. 
     In a broad aspect, the present invention is directed to a portable gas chromatograph. Suitably, the chromatograph being portable, is between about 15 and 25 pounds. 
     The portable gas chromatograph includes at least one pre-concentrator, a first separation column, a second separation column, a first detector in communication with the first separation column and a second detector in communication with the second separation column. 
     In one embodiment, the detectors further have output signals which are connected to a signal processing unit. In specific embodiments, the signal processing unit includes, among other features, analog processing electronics, digital processing electronics in communication with the analog processing electronics, a central processing unit, and a recognition library. 
     In another embodiment, the signal processing unit is equipped with a wireless radio that may communicate with a computer within a given range of operation. 
     Turning now to the figures,  FIG. 1  is a block flow diagram illustrating an embodiment of the gas chromatograph system according to the invention. Air is extracted from the surrounding environment into the pre-concentrator ( 1 ) using any suitable method known in the art such as via means of an air pump. Inside the pre-concentrator ( 1 ), the desired analytes are pre-concentrated to remove moisture to facilitate an increase in the size of the chromatographic peak achieved. Therefore, absorbents or adsorbent traps such as molecular sieves are employed. One example of a suitable adsorbent trap is graphitized carbon-based molecular sieve available from Alltech Associates Inc. (Alltech Associates, Inc., is a wholly owned subsidiary of W. R. Grace &amp; Co. in Columbia, Md.) under the tradename of Tenex®. 
     The pre-concentrator may also be referred to as a thermal desorption tube. 
     Various methods have been suggested to pre-concentrate analytes. For example, see U.S. Pat. Nos. 2,813,010, 4,245,494, 4,293,316, 5,612,225, 6,223,584, 6,652,625, 6,814,785, 6,977,459, each of which is incorporated by reference herein in its entirety. 
     The pre-concentrator ( 1 ) is also suitably equipped with a heater and heater electronics. Upon heating, the analyte is released into a carrier gas stream. In this embodiment, the carrier gas is helium. However, other suitable carrier gases include hydrogen and nitrogen, for example. Heating of the pre-concentrator is desirable because higher sample equilibrium temperatures can result in much larger chromatographic peaks. 
     From the pre-concentrator ( 1 ), the analyte in the carrier gas is then flowed substantially simultaneously into a first separation column ( 10 ) and a second separation column ( 20 ). The separation column(s) of the GC system contains the stationary phase through which the carrier gas with the analytes is flowed. The separation columns may contain any of a variety of suitable stationary phases. ( 1 ) 
     Suitably, the stationary phase is formed using with a polymer material. Examples of suitable stationary phases include, but are not limited to, polydimethylsiloxane, polyethylene glycol and polyester polymers. Typically, the stationary phase is of a relatively high molecular weight. 
     Suitably, in the embodiment illustrated in  FIG. 1 , one of the columns  10 ,  20  includes a non-polar stationary phase, and one of the columns  10 ,  20  includes a polar stationary phase. 
     The nonpolar end of the spectrum is polydimethyl siloxane, which can be made more polar by increasing the percentage of phenyl groups on the polymer. For very polar analytes, polyethylene glycol (a.k.a. carbowax) is commonly used as the stationary phase. In the embodiment described above, for example, one column includes a stationary phase which is polydimethylsiloxane, a relatively non-polar molecule, and one column includes polyethylene glycol, a relatively polar molecule. After the polymer coats the column wall or packing material, it is often cross-linked to increase the thermal stability of the stationary phase and prevent it from gradually bleeding out of the column. 
     Suitably, the separation columns have a length of about 15 meters or longer. However, the separation columns are fitted into a small, compact portable unit as disclosed herein. As such, the separation columns are suitably configured into a gas chromatograph column assembly (GCCA). One suitable configuration for the separation columns disclosed herein is found in commonly assigned copending U.S. patent application entitled Gas Chromatograph Column Assembly GCCA, the entire content of which is incorporated by reference herein. The GCCA is discussed in more detail with reference to  FIGS. 14-26  found below. 
     In the embodiment shown in  FIG. 1 , first column  10  is in fluid communication with a first detector  15  and second column  20  is in fluid communication with a second detector  25 . 
     Any suitable detector may be employed herein. Examples of suitable detectors include, but are not limited to, atomic emission, chemiluminescence, electron-capture (ECD), flame ionization (FID), photoionization (PID), mass spectrometer (MS), thermal conductivity (TCD), flame photometric (FPD), infrared (IFD), Fourier Transform infrared (FTIR), ultraviolet/visible, far ultraviolet absorbence (FUV) and nitrogen phosphorous (NPD). Detectors suitable for use in combination with gas chromatograph systems are disclosed in U.S. Pat. Nos. 6,952,945, 6,837,096, 6,627,454, 6,524,527 and 5,108,466, each of which is incorporated by reference herein in its entirety. 
     An example of a particular TCD type detector suitable for use herein is disclosed in commonly assigned copending patent application entitled Compact Thermal Conductivity Detector, the entire content of which is incorporated by reference herein. An example of a specific TCD detector employed in combination with a GC according to the invention is discussed in more detail with reference to  FIGS. 27-32 . 
     Suitable detectors  15 ,  25  have the sensitivity to measure chemicals at a concentration of parts per one hundred million to parts per billion. 
     From detectors  15 ,  25 , the gas with the analytes, is exhausted back into the environment. 
     Detectors  15 ,  25  measure each analyte and provide a signal to the signal processing unit. The signal processing unit is discussed in more detail with reference to  FIG. 9  below. The signal processing unit includes analog signal processing electronics, digital signal processing electronics, and a central processing unit (CPU) The CPU records the signature of the chemical. A recognition library is also suitably incorporated into the CPU. The signature of the chemical is then compared to those in the recognition library and the chemical can be identified. The CPU then sends the data to a display  16 . 
       FIG. 2  is an enhanced block flow diagram of a GC according to the invention. A carrier gas supply  12  is coupled with a pressure regulator  18  for controlling/reducing the pressure of the gas and a flow controller  22  for further maintaining gas flow rate to the GC columns  15 ,  25 . The pressure regulator is selected from any suitable configuration. A specific example of a pressure regulator employed in combination with the GC according to the invention is disclosed in commonly assigned copending entitled Very Small High Pressure Regulator, the entire content of which is incorporated by reference herein in its entirety. 
     The gas pressure of the carrier gas is regulated so that the sample flow of gas through the system can be controlled to a consistent flow whether the carrier gas in the tank is at a pressure of 2000 psi or 300 psi. 
     An embodiment of a specific gas pressure regulator employed herein is discussed in more detail below with reference to  FIGS. 33-42 . 
     The flow controller allows the gas flow to be selectively set and maintained. 
     The carrier gas is selected from any suitable inert gas including, but not limited to, hydrogen, helium and nitrogen. In the embodiment shown in  FIG. 2 , helium is shown as the carrier gas. 
     In the embodiment shown in  FIG. 2 , from the carrier gas supply  12 , the gas is delivered via the flow controller  22  to a multiport valve  24  having switchable arrangement to allow for switching between operating states which will be explained more fully below. In a first operating state, however, sample is extracted from the surrounding environment through filter  26   
     A sample is extracted from the environmental surroundings through a filter  26 . The sample is then passed through a dopant chamber  28  where it is mixed with reference chemical. A reference chemical is employed for removing errors caused by variations in temperature and/or pressure. As will be explained more fully below, the reference chemical has a known signature and any required correction for error based on the known signature is accomplished via signal processing software which provides a correction factor that will be applied against the other analytes in the sample being analyzed. A reference chemical is therefore included as part of each sample analysis. 
     The sample and the reference chemical are moved via the multiport valve  24  to the pre-concentrator  1 , and from there directed to GC columns  10 ,  20 . GC columns  10 ,  20  are in fluid communication with detectors  15 ,  25 . Each detector  15 ,  25  is has its own output signal and each detector is in communication with a signal processing unit  14 , which in  FIG. 2  is shown broken down into a signal conditioning system  32  and a digital processing system  34 . 
     As shown in  FIG. 2 , each GC column  10 ,  20 , is equipped with its own heater  35 ,  45  respectively, each heater having its own heater electronics. This allows heating of each column  10 ,  20  to be heated from ambient temperatures to over 200° C. uniformly across the column length. It is also desirable that each column can be cooled between samples to ambient temperature within several minutes to allow for repeated sample measurements in short time periods. 
       FIG. 3  is a pneumatic block flow diagram of the GC according to the invention which is a more detailed flow diagram of an embodiment similar to that shown in  FIG. 2 . In the embodiment shown in  FIG. 3 , the multiport valve  24  is shown as a 10-port valve having two positions, position A and position B. 
     In position A, a sample can be loaded.  FIG. 4  is a schematic diagram of a multiport valve system  24  employed in the embodiment in  FIGS. 2 and 3  shown in position A. A carrier gas, in this case helium, is provided from helium supply tank  12  (through valves as shown in  FIG. 3 ) through regulator  18  through sample loop  33  through columns  10 ,  20  and detectors  15 ,  25  out exhaust ports  38 ,  40 . When columns  10 ,  20  and detectors  15 ,  25  are on and being heated, carrier gas, i.e. in this embodiment helium, will be flowing through them. From a cold start-up, helium will flow until the unit reaches its predetermined operating temperature. 
     Once analysis is begun, typically by an operator activating a start button, in this embodiment the sample pump  30  is activated and a sample will be drawn through an inlet port designated at  36  (through valves as shown in  FIG. 3 ) and to the pre-concentrator  1 . From the pre-concentrator  1  the sample flows (through valves as shown in  FIG. 3 ) through the sample pump and out exhaust port  42 . 
     A sample can be advanced to the GC columns  10 ,  20  when the multiport valve is advanced to position B. The multiport valve  24  is then switched to position B which is shown as a schematic diagram in  FIG. 5 . The pre-concentrator  1  is then heated (pre-concentrator is equipped with a heater and heater electronics as discussed above) which releases a cloud of the now concentrated sample. Helium flows from the regulator  18  (through valves  22 A,  22 B as shown in  FIG. 3 ) through the pre-concentrator  1  (through valves as shown in  FIG. 3 ) through the sample loop  32  (through valves as shown in  FIG. 3 ) and out the exhaust port  42 . Once the sample is caught in the sample loop, the multiport valve is switched back to position A. This only takes a short period of time. The sample loop  33  provides an internal volume for temporary storage of the concentrated sample provided from the pre-concentrator  1 . 
     The sample can then be analyzed once the multiport valve  24  is again returned to position A. Again in position A, helium flows from carrier gas supply  12  (through valves  22 A,  22 B as shown in  FIG. 3 ) through the sample loop  33  (through valves as shown in  FIG. 3 ) and through the GC columns  10 ,  20  and to the detectors  15 ,  25 . The carrier gas flowing through the system carries the now concentrated sample from the sample loop  33  to the GC columns  10 ,  20  and to the detectors  15 ,  25  for analysis. The multiport valve  24  can then be returned to position B for cleaning. 
     Once analysis is complete, multiport valve  24  is again switched to position B where helium continues to flow from the carrier gas supply  12  for clearing sample from the pre-concentrator  1  and the sample loop  33 . 
       FIG. 6  illustrates one embodiment of a multiport valve  24  employed in the GC according to the invention. The multiport valve  24  in this embodiment is shown having ten ports  46 . 
       FIG. 7  is a side view of an embodiment of a gas chromatograph  5  according to the invention. The GC columns  10 ,  20  and multiport valve  24  are held within casing  44 . The carrier gas supply  12 , flow control valve  22  and chamber  28  for the reference chemical are clearly seen. 
       FIG. 8  is an end view of a gas chromatograph according to the invention with interior parts exposed. GCCA&#39;s  9 ,  19  each include a GC column  10 ,  20 . A multiport valve  24  is located between and is in communication with GC columns  10 ,  20  Sample loop  33  is clearly visible above the multiport valve  24 . 
       FIG. 9  shows a block diagram schematic of the electrical portion  50  of the portable gas chromatograph system. The system is powered by a 14.4 volt rechargeable Lithium battery  52 , in an embodiment of the invention, although any commercially available battery could be utilized with the system, if desired. Battery  52  supplies power to power supplies  54 , which after suitable conditioning, provide power to the various electronic components of the system. Either an AC or a DC power system is employed for driving the electronics, heaters and detectors in the system. The analog board  32 , which is also referred to in  FIG. 2  as the signal conditioning system  32 , controls and calibrates the detectors  15  and  25 . The digital board  34 , which is also referred to in  FIG. 2  as the digital processing system  34 , converts the very small (microvolts) analog signals output by analog board  32  into accurate digital signals. The Central Processing Unit (CPU)  56  is programmed to perform signal processing to build a signature of the sampled chemical and identify the constituent chemicals, if present in the identification database, which is stored in Flash non-volatile memory which is loaded into RAM for real-time processing when the CPU  56  boots up. The measurements made in the field are also stored in the RAM in real-time and then written to the Flash memory as a background operation. The CPU  56  is also programmed to maintain the identification database, interact with the operator controls  58 , and displays data on the display  60 , such as the chemical identified. The system also has the capability to wirelessly communicate with an external computer via a remote data link, which can be any desired wireless link, but in an embodiment is a BlueTooth radio link  62 . The BlueTooth radio link  62  allows wireless communication with an external computer up to 100 meters away from the portable system. Link  62  allows the detected chemical signature to be sent to the external computer for emailing to any desired person(s) or system(s). A maintenance port  64  is provided to allow an external system to be connected to the electronics, and in an embodiment the maintenance port is an RS-232 port. The analog systems section  66  portion of digital board  34  provides seven closed loop PID (Proportional, Integral, Derivative) control loops for controlling the TDT (Thermal Desorption Tube i.e. the Preconcentrator) Heater; the two GC heaters; the two TCD heaters; the valve heater (which heats valve  24 ) and the TDTT heater, which heats the TDT transfer line. 
     As air is sucked through the Preconcentrator/TDT  24 , gas molecules are trapped in the storage chemical inside. Once enough sample is collected, the outside air flow is stopped, the Preconcentrator TDT Heater turns on and heats the Preconcentrator/TDT for a short period of time. This heat boils off the trapped molecules and releases a cloud of concentrated sample molecules. This cloud is what is transferred into the GCs  10  and  20 . The TDTT heater mildly heats the transfer lines around the Preconcentrator/TDT  24  so that the hot gases released by heating the Preconcentrator/TDT  24  do not immediately condense in the colder pipes around the TDT  24 . Analog systems section  66  also includes the temperature controllers with PWM (pulse width modulated) outputs, a 16 channel 16 bit analog to digital converter and an 8 channel 16 bit digital to analog converter. Pressure sensor condition  68  is connected to the pressure sensor of regulator  18  (discussed in more detail further below). Ambient temperature sensors  70  are provided. Valve motor  72  is connected to the valve motor controller  74  via H. Bridge  76 , as is well known in the art. Valve controller  74  controls the position of the  10  port two position valve  24 . A FPGA peripheral controller/data formatter is shown at  78  and pulse width modulated motor controllers are shown at  80 , which control air pump  30  and fans  82 . 
       FIG. 10  shows a block diagram of the digital circuitry of digital board  34 . The ambient temperature sensors  70  receive temperature inputs from the various subsystems, such as the GC columns  9  and  19 , the detectors  15  and  25  etc. The temperature sensors are in turn input to the PWM motor controllers  80 , which control the air pump  30  and fans  82 . This block diagram also shows a debug port provided to the digital board  34 , which in an embodiment is a USB port  84 . 
       FIG. 11A  is an electrical circuit schematic showing the TCD bridge analog to digital circuit. In some embodiments, two TCD bridge circuits are provided, to connect the two TCD detectors  15  and  25  to the FPGA peripheral controller/data formatter  78 . 
       FIG. 12  shows a system firmware context diagram, which shows that the Chem-ID firmware  90  interacts with the user via switches (or buttons)  58  and via display  60 . The system firmware can also interact with a user via LED  91  or beeper  92 , as well as by emailing a user using BlueTooth radio link  62  and an external computer which is connected to the internet. The ambient temperature sensors  70  input their temperatures to the firmware  90 . A real-time clock  93  interacts with firmware  90 . The firmware  90  interacts with the heaters control  66 . The firmware  90  controls the detector hardware, namely the air pump  30 , the multiport valve  24  and the TCD detectors  15  and  25 . The firmware  90  controls the power control  54 . The firmware  90  interacts with the communications subsystems, namely the maintenance port  64  an IrDA port  94  and the Bluetooth data link  62 . 
     Gas Chromatograph Column Assembly 
       FIG. 13  illustrates an embodiment of a gas chromatograph with interior parts visible. In particular, a gas chromatograph column assembly as described below can be seen in the interior.  FIGS. 14-26  illustrate an embodiment of the Gas Chromatograph Column Assembly (GCCA)  102 . The GCCA  102  is utilized in the over all system described herein.  FIGS. 14-15  show different perspective views of the GCCA  102 . The GCCA  102  has a housing  103  that houses a separation column  10  or  20 . The housing  103  includes an insulated valve housing  104 , a column housing  106  and a port plate  108  fitted together. The port plate  108  defines an intake port  110  and an exhaust port  112 . The insulated valve housing  104  and the column housing  106  define an opening  114  to receive a detector  116  and an inlet port  118  to receive a sample to be tested. 
     The valve housing  104  housing functions as a bottom plate of the GCCA  102 . However, extensions  105  from a left hand GCCA  102  ( FIG. 14 ) cooperate with extensions  105  from a right hand GCCA  102  ( FIG. 15 ) to form a housing and insulation for the rotary valve for the overall GC System. As mentioned above, the overall GC System includes a left hand GCCA and a right hand GCCA. One includes separation column  10  and the other includes separation column  20 . The discussion herein applies to both. It should be understood that the extensions  105  may be excluded when discussing the GCCA  102  as a stand alone unit, such as shown in  FIG. 23 . 
       FIG. 16  shows the GCCA  102  with the column housing  106  and port plate  108  being transparent to reveal the column and support structure  120 , a cooling fan  122 , such as, but not limited to, a forced convection (fan), and the detector  116 . A sample to be analyzed is introduced into an end of the column  10  through the inlet port  118 . The detector  116 , which is connected to the remaining end of the column, detects the exiting sample. 
       FIGS. 17 and 18  show blow-up views of the GCCA  102  showing the GCCA&#39;s  102  construction and arrangement.  FIG. 17  shows a left hand GCCA  102  and  FIG. 18  shows a right hand GCCA  102 . The left hand and right hand GCCAs  102  differ only in that the inlet port  118 , the detector opening  114  and the intake  110  and exhaust  112  ports are on opposite sides. 
     As shown in  FIGS. 17 and 18 , the valve housing  104  is configured to receive the column support  124 . The central portion  126  of the valve housing  104  has wells  128  circumferentially dispersed around a center portion  130 . The wells  128  are separated by raised portions  132  that extend from the center portion  130  to a periphery  134  of the central portion  126 . As, can be seen in the figures, portions  118 ,  114 , are also configured to form the inlet port  118  and the detector opening  114 . 
     In some embodiments, the valve housing  104  is made from low density rigid foam, such as, but not limited to, light weight polymethacrylimide. In one embodiment, the valve housing  104  is made from Rohacell RIMA  71  composite foam. Such materials provide a high degree of insulation and resist high temperatures. The valve housing  104  is formed by suitable means, including, but not limited to, machining and molding. 
     The column support  124  sits in the central portion  126  of the valve housing  104 . As shown in  FIG. 19 , the column support  124  is ring-shaped and has circumferentially spaced bridges  136  extending the width of the column support  124 . The bridges  136  are raised from the outer surface  138  of the column support  124  and extend laterally from one of the side edges  142  of the column support  124  to form lateral posts  140 . 
     In some embodiments, the column support  124  is made from low density rigid foam, such as, but not limited to, light weight polymethacrylimide. In one embodiment, the column support  124  is machined from a slab of Rohacell RIMA 71 composite foam. Such materials provide a high degree of insulation and resist high temperatures. 
     The tubing  144  that makes up the separation column  10  is wrapped around the column support  124 , resting only on the bridges  136 . The bridges  136  include radially extending end posts  146  that bookend the wrapped tubing  144 . The radially extending end posts  146  extend above the wrapped tubing  144 . In some embodiments, the top surface  174  of the bridges  124  is threaded so as to receive individual windings of tubing  144  and serves to further limit movement of the tubing  144  on the bridges  136 . 
     As shown in  FIG. 17 , the separation column  10  is wrapped around the column support  124 . This combination, in turn, is optionally wrapped with insulation  148 . An example of the insulation includes, but is not limited to, a polyamide tape. The combination is set in the valve housing  104  with the lateral posts  140  of the column support  124  resting on the raised portions  132  of the central portion  126  of the valve housing  124 . 
     The column support  124  also includes openings  150  and  152 .  150  and  152  are holes that allow the ends of column tubing  144  to leave the column support  124 . As shown in  FIGS. 18 and 19 , the column support  124  includes a slot  156  to receive a temperature sensor  154  to monitor the temperature of the column  10 . 
       FIG. 20  shows a side view of the column support  124  cleaved along its circumference.  FIG. 21  shows a blown up partial view of  FIG. 20 . As can be seen, the tubing  144  is wrapped around the column support  124  and rests on the bridges  136  between the radially extending end posts  146  of the bridges  136 . 
     Returning now to  FIGS. 17 and 18 , the cooling fan  122  is position within and is connected to the column housing  106  via suitable means. In the embodiment shown, the cooling fan  122  is attached to the column housing  106  via screws  157 , nuts  158  and washers  160 . The column housing  106  is then positioned over the column support  124  and on the valve housing  104 , enclosing the column support  124  and the cooling fan  122 . 
     The column support housing  106  includes a central opening  166  positioned over the fan blades  123  of the cooling fan  122 , which is positioned at least in part within the circumference of the column support, so as to allow heated air drawn up by the cooling fan to vent. A plurality of intake vents  168  is dispersed in the column housing  106  around the central opening  166 . When the column housing  106  is positioned over the column support  124  and on the valve housing  104 , the intake vents  168  are position at least in part outside of the circumference defined by the of the outer surface  138  of the column support  124 . 
     In some embodiments, the column support housing  106  is made from low density rigid foam, such as, but not limited to, light weight polymethacrylimide. In one embodiment, the column support housing  106  is made from Rohacell RIMA 71 composite foam. Such materials provide a high degree of insulation and resist high temperatures. The column support housing  106  is formed by suitable means, including, but not limited to, machining and molding. 
     The detector  116  is positioned within the detector opening  114  formed between the valve housing  104  and column housing  106  and is secured via suitable means. In the embodiment shown, the detector  116  is attached via screws  162  and split lock washers  164 . 
     The port plate  108  is positioned over the column housing  106  and secured to the valve housing  104  and the column housing  106  by suitable means. In the embodiment shown, it is secured via threaded inserts  167  and screws  169  as shown. 
     In some embodiments, the port plate  108  is made from low density rigid foam, such as, but not limited to, light weight polymethacrylimide. In one embodiment, the port plate  108  is made from Rohacell RIMA 71 composite foam. Such materials provide a high degree of insulation and resist high temperatures. The port plate  108  is formed by suitable means, including, but not limited to, machining and molding. 
       FIG. 22  shows a partial cross-section of the column support  124  along lines  19 B- 19 B of  FIG. 19 . The cross-section is cut through one of the bridges  136 . The column support  124  extends downward back into the page showing the inner surface  170  of the column support  124 . In the embodiment shown, the tubing  144  that makes up the column  10  extends around the column support  124  forming two rows  171 ,  172 . Resistive heat wire  155  is wrapped between and is in contact with the rows  171 ,  172 , of tubing  144 . The resistive heat wire is in contact with a power source and is used to heat the column  10 . It should understood that there may be one or more rows of tubing depending upon the length of the column tubing  144  and/or the width of the column support bridges  124 . 
     As mentioned above, in some embodiments, the top surface  174  of the bridges  124  is threaded so as to receive individual windings of tubing  144  and serves to further limit movement of the tubing  144  on the bridges  136 . This maintains the geometry between the coils of the wrapped column tubing  144  and the heating wire and fixes them with respect to each other over the entire length of the column. This maintains uniformity and accurate heating of the column  10  to producing accurate and repeatable measurements. 
       FIG. 23  is a cut away illustration showing the inner chamber  175  of the GCCA  102 . As can be seen, the port plate  108  and the support column housing define an intake chamber  176 . The intake chamber  176  is in fluid communication (including gaseous communication) with and receives outside air from the intake port  110 . The intake chamber  176  extends 360° around the central opening  166  of the support chamber housing  106 . Air is drawn into the intake chamber  176  by the cooling fan  122  and down through the intake vents  168  of the support chamber housing. As shown in  FIG. 23 , the cooler air is drawn down over the column tubing  144 , which is positioned between the side walls  177  of the column support housing  106  and the outer surface  138  of the column support  124 . Since the column tubing  144  is raised above the outer surface  138  by the bridges  136  and separated from the side walls  177  of the column support housing  106  by the radially extending end posts  146 , the cooling air travels over the inner  178  and outer  179  surfaces of the column  10 . 
     As can be seen in  FIG. 23 , the lateral posts  140  of the support column  124  sit on the raised portions  132  of the valve housing  104  forming exhaust vents  180  allowing the intake chamber  176  to be in fluid communication with the inner chamber  175 . The air that is drawn down over the column  10  is allowed to escape into the inner chamber  175  through the exhaust vents  180 . As the air passes over the heated column tubing  144  and resistant heat wire  155 , it is heated. The cooling fan  122  purges the hot air by drawing it into the inner chamber  175  and out through the central opening  166  of the column support housing  106  into an exhaust chamber  182  and out of the exhaust port  112 .  FIGS. 24 and 25  show further views of an embodiment of the GCCA  102 . 
     The GCCA  102  allows for rapid cooling via forced convection (fan). The low thermal mass of the column  10 , and the fact it is suspended in the air, support rapid cooling. The fan  122  draws air directly across the column  10  and exhausts through the center  166  of the system. This flow prevents heated air from flowing across any other part of the column  10  or column support  124 . 
     The GCCA  102  is designed to allow columns of any material to be installed. Examples of usable column materials include, but are not limited to fused silica (i.e. glass) and stainless steel. In some embodiments of the invention, the column length is greater than or equal to 50 feet of capillary column. In other embodiments, the column length is greater than or equal to 52.5 feet capillary column. The GCCA  102  is constructed such that columns, such as columns made of stainless steel of such length, may be used in a form factor less then 3.25 inches in diameter while still maintaining integrated, precision heating. 
       FIG. 26  illustrates a non-limiting example of a cross-section of column tubing. As shown, in some embodiments the column tubing  144  has a polyimide outer coating  190  surrounding a silica layer  192  which in turn surrounds a layer of stationary phase  194 . Examples of stationary phases, in addition to the ones mentioned above, include, but are not limited to, polydimethylsiloxane (DB-1) and polyethylene glycol (DB-WAX). 
     In some embodiments of the invention, the column  10  is heated to over 200° C. within 2 minutes and back down to ambient temperature within 3 minutes. 
     In some embodiments, the resistive heat wire is coated with an insulation coating, such as, but not limited to, a polyamide coating. 
     In some embodiments, the design of the GCCA  102  is such that it may be in close proximity to electronic devices, such as those contained in the Portable Gas Chromatograph described herein, and the detector  116  without damaging the solder on electronic boards or affecting the accuracy of the detector  116 . 
     In some embodiments of the invention, the GCCA  102  is less than 0.5 lbs and in one embodiment it is about 0.425 lbs. In some embodiments, the GCCA  102  is less than 5.50 inches long from inlet port  110  to exhaust vent  112 , less than 3.6 inches wide from the outside edge of the housing to one half of the valve housing and less than 4.2 inches tall. 
     Compact Thermal Conductivity Detector 
       FIG. 27  shows an exploded view of an embodiment of a compact thermal conductivity detector  410  that is suitable for use as a detector  15  in various embodiments of a gas chromatograph  5  as described herein. The thermal conductivity detector  410  determines the thermal conductivity of a gas in a flowing gas stream by measuring the electrical resistance across a thermistor  414  as the gas stream being analyzed flows over the thermistor  414 . As particles in the gas stream of varying size, density and/or molecular weight pass across the thermistor  414 , the temperature of the thermistor  414  varies, thereby varying the resistance across the thermistor  414 . The resistance is measured to a microvolt level of precision and is thus susceptible to errors induced by temperature fluctuations induced from outside of the detector  410 . Therefore, the temperature of the detector  410  is controlled and regulated, and insulative materials are used in forming the detector  410  as described herein. In some embodiments, the detector  410  is manufactured such that any portions of the detector  410  in contact with the flowing gas stream are substantially chemically inert. 
     The detector  410  comprises the thermistor  414 , a sensor housing  420 , a body housing  430 , a first end plate  440  and a second end plate  450 . Contact pins  422  that pass through the sensor housing  420  are electrically attached to the thermistor  414  and comprise a portion of the thermistor  414  electrical circuit. Internal cavities in the sensor housing  420  and body housing  430  form a gas analysis chamber in which the thermistor  414  is located. The gas analysis chamber is shown in greater detail in  FIG. 32 . The flowing gas stream  412  to be analyzed enters the gas analysis chamber through a fluid inlet passageway  432  in the body housing  430 . The gas stream exits the gas analysis chamber through a fluid outlet passageway  426  in the sensor housing  420  and a flow tube  460  in fluid communication with the fluid outlet passageway  426 . 
       FIG. 28  shows an embodiment of a sensor housing  420  partially assembled with contact pins  422  and a thermistor  414 . The sensor housing  420  is desirably made from stainless steel or any other suitable non-reactive material capable of withstanding temperatures over 100° C. The sensor housing  420  comprises an internal cavity  424  that forms at least a portion of the gas analysis chamber. The sensor housing  420  further comprises a bore  423  for each contact pin  422 . In some embodiments, each bore  423  runs parallel to the fluid outlet passageway  426 . In some embodiment, a portion of each bore  423  overlaps the internal cavity  424 , or alternatively, a channel  428  is formed between each bore  423  and the internal cavity  424  so that the thermistor leads  416  do not contact the sensor housing  420 . 
     Each contact pin  422  is insulated from the sensor housing  420 , for example using an insulating sleeve  464  comprising polytetrafluoroethylene (PTFE) or any other suitable insulating material. In some embodiments, the insulating sleeves  464  are suitable to both thermally and electrically insulate the contact pins  422  from the sensor housing  420 . The contact pins  422  and insulating sleeves  464  are secured to the sensor housing  420  using any suitable method. In some embodiments, the contact pins  422  and insulating sleeves  464  are friction fit within their respective bores  423 . In some embodiments, the contact pins  422  and insulating sleeves  464  are bonded to the sensor housing  420  using a curable composition that will resist chemical degradation, such as an epoxy. 
     In some embodiments, the thermistor  414  comprises a commercially available microthermistor such as a Bead Microthermistor available from YSI Temperature of Dayton, Ohio. In some embodiments, the thermistor  414  is coated in glass and comprises two electrical leads  416 . The leads  416  may comprise platinum-iridium, platinum, gold, copper and/or other suitable conductive materials or alloys thereof. 
     The thermistor  414  is centered between the contact pins  422  and aligned along the longitudinal axis of the fluid outlet passageway  426 . Thus, the thermistor  414  is oriented directly in the flow path of the gas stream. Each electrical lead  416  is electrically connected to a contact pin  422 , for example by soldering. In some embodiments, the electrical leads  416  and the connections between the leads  416  and the contact pins  422  are coated with a curable composition such as an epoxy. Such a coating provides a further mechanical connection between the leads  416  and the contact pins  422 , provides support to the leads  416  against strain and vibration, and also provides a chemical barrier between the flowing gas stream and potentially reactive material(s) used to form the leads  416  and the contact pins  422 . 
     Passing the contact pins  422  through the sensor housing  420  and having the contact pins  422  mechanically supported by the sensor housing  420  prevents external loading and vibrations present in the distal portions  421  of the contact pins  422  from damaging the thermistor  414  or the thermistor leads  416 . Thus, the sensor housing  420  allows the thermal conductivity detector  410  to be rugged and useable in field applications. 
     Referring again to  FIG. 27 , the body housing  430  comprises an internal cavity  434  that receives the sensor housing  420 . The body housing  430  is desirably made from the same material as the sensor housing  420  or any other suitable and compatible material. In some embodiments, the inner surface  435  of the internal cavity  434  and the outer surface  433  of the sensor housing  420  comprise complimentary threadings. 
       FIG. 29  shows a sensor housing  420  assembled with the contact pins  422  visible and the body housing  430  oriented to receive the sensor housing  420 . The sensor housing  420  is inserted/threaded into the internal cavity  434  of the body housing  430 , thereby sealing the thermistor  414  within the gas analysis chamber formed by the internal cavities  424 ,  434  of the sensor housing  420  and the body housing  430 . In some embodiments, the sensor housing  420  is further secured to the body housing  430  using a curable composition such as an epoxy. The use of a curable composition further ensures that the gas analysis chamber is hermetically sealed against all air flow except the gas flow being analyzed. 
     An electrical insulator  462  of any suitable material is oriented about the body housing  430 . In some embodiments an insulator  462  comprises PTFE, such as 3 mil PTFE tape that is wrapped about the body housing  430  at least one time and in some embodiments four or more times. In some embodiments, the body housing  430  comprises external threadings  436 , and the insulator  462  is desirably thin and flexible enough to conform to the root radius of the threadings  436 . 
     A heating device  466  is then oriented about the insulated body housing  430 . In some embodiments, the heating device  466  comprises a resistive heating wire comprising Nickel Chromium or other suitable metals and/or alloys. When the heating device  466  comprises a wire, it is desirably wrapped into the root radius of the external threadings  436  of the body housing  430 , and thus comprises a suitable size, such as 30 AWG. A second layer of electrical insulator  462  is then oriented about the body housing  430  to further insulate the heating device  466 . 
     Referring to  FIGS. 27 and 30 , the second end plate  450  comprises an insulative material capable of withstanding temperatures of 100° C. or greater. The material is further capable of being formed or machined to the specific shapes required. In some embodiments, the second end plate comprises G10 epoxy impregnated laminate, for example as available from American Micro Industries, Inc. of Chambersburg, Pa. 
     The second end plate  450  comprises a plurality of securement apertures  452  (see  FIG. 27 ). A plurality of fasteners  468  pass through the securement apertures and are received in securement cavities  438  in the body housing  430 . The second end plate  450  further comprises a channel  456  for each contact pin  422  and a central aperture  458 . Each contact pin  422  passes from the sensor housing  420  through the central aperture  458 , and is then oriented within its respective channel  456 . The contact pins  422  are then electrically connected to the analog signal processing section  32  (see  FIG. 9 ) of the gas chromatograph  5  control system. 
     In some embodiments, a flow tube  460  is placed in fluid communication with the fluid outlet passageway  426  of the sensor housing  420 . The flow tube  460  passes through the central aperture  458  of the second end plate  450  and directs the flow of the gas stream exiting the thermal conductivity detector  410 . In some embodiments, the flow tube  460  comprises stainless steel and is bonded to the sensor housing  420  using a curable composition. 
     In some embodiments, body housing  430  further comprises a temperature sensor cavity  431 , and the second end plate  450  further comprises a temperature sensor aperture  451  and a sensor channel  453 . Thus, a temperature sensor  470  is placed within the temperature sensor cavity  431  and the associated wiring  471  passes through the temperature sensor aperture  451  and is oriented within the sensor channel  453 . The temperature sensor  470  detects the temperature of the thermal conductivity detector  410  and reports the temperature to the analog systems section  66  of the gas chromatograph 5 control system (see  FIG. 9 ). 
     Referring to  FIG. 30 , in some embodiments the second end plate  450  further comprises heating wire apertures  474  and heating wire channels  475 . The ends of a heating wire  466  that is wrapped about the body housing  430  extend through the heating wire apertures  474  and are oriented within the heating wire channels  475 . The ends of the heating wire  466  are then electrically connected to the analog systems section  66  of the gas chromatograph 5 control system (see  FIG. 9 ). The analog systems section  66  controls the temperature of the thermal conductivity detector  410  by increasing and/or decreasing the current flowing through the heating wire  466 . The analog systems section  66  adjusts the current in the heating wire  466  based upon the temperature of the thermal conductivity detector  410  as reported by the temperature sensor  470 . 
     The second end plate  450  further comprises at least one mounting aperture  454  used to secure the thermal conductivity detector  410  to the rest of the device. For example, in some embodiments the thermal conductivity detector  410  is received in opening  114  in the GCCA  102  (see  FIG. 18 ), and fasteners pass through the mounting apertures  454  and into a portion of the GCCA housing. 
       FIG. 31  shows the first end plate  440  secured to the body housing  430  using fasteners  468 . The first end plate  440  is desirably made from the same material as the second end plate  450  or another suitable insulative material. 
     In some embodiments, the body housing  430  further comprises a fitting  437  in conjunction with the fluid inlet passageway  432 . The fitting  437  may be used to attach the thermal conductivity detector  410  to the column tubing  144  from the GCCA  102  (see  FIG. 22 ) to receive the gas stream. In some embodiments, the fitting  437  comprises internal threadings. 
     Referring again to  FIG. 27 , in some embodiments, the first end plate  440  comprises an aperture  442  shaped to receive the fasteners  468  and the fitting  437 . 
     In some embodiments, the first end plate  440  and the second end plate  450  may each comprise a plurality of alignment pin apertures  448  or blind holes. Alignment pins  446  are then used to aid in assembly and alignment of the end plates  440 ,  450 . 
       FIG. 32  shows a sectional view of an embodiment of a thermal conductivity detector  410 , for example as taken across line  32 - 32  of  FIG. 31 . The gas analysis chamber  478 , formed by the internal cavities of the sensor housing  420  and the body housing  430 , is visible with the thermistor  414  suspended therein. Similar reference numerals are used to denote similar features as shown and described with respect to  FIGS. 27-31 . 
     Very Small High Pressure Regulator (VSHPR) 
     Referring now to  FIG. 33 , there is shown a partially transparent view of the Very Small High Pressure Regulator (VSHPR) ( 18 ). In at least one embodiment, the VSHPR ( 18 ) is a component of a Gas Chromatograph. In at least one embodiment, the VSHPR ( 18 ) is a stand alone device not connected to a Gas Chromatograph. The VSHPR ( 18 ) regulates the flow and pressure of a gas stream which enters from a source (not shown) and subsequently exits out of one or more outlets ( 208 ) positioned at the opposite end of a gas flow path ( 245 ). The gas flow path ( 245 ) of the VSHPR ( 18 ) comprises two or more gas stages ( 228 ) which work together to reduce the pressure of received input gas from as high as 3000 psi to a constant output pressure which can be as low as 30 psi. In at least one embodiment, the VSHPR ( 18 ) is calibrated for any input or output pressure within the 3000-30 psi range and is accurate with a precision of +/−1 psi. In at least one embodiment, the VSHPR ( 18 ) has small compact dimensions and is designed to fit in any portable or hand held equipment that uses high pressure gas. In at least one embodiment, the VSHPR has dimensions of 1.25″×2.75″×4.64″. 
     In at least one embodiment, the VSHPR reduces the pressure from 2000 psi to 40 psi. 2000 psi is a common pressure level in gas sources such as commercially available gas tanks or bottles and in particular of helium gas bottles. The regulation to a constant and stable pressure of  40  psi allows the gas stream to be properly used by other components of the Gas Chromatograph. The VSHPR ( 18 ) can regulate a gas stream consisting of a gas selected from the list of helium, hydrogen, any other gas with a molecular mass greater than helium, and any combination thereof In at least one embodiment the VSHPR ( 18 ) comprises one or more O-Rings and/or one or more lubricants (including but not limited to polysiloxane) and/or one or more sealants to assure that the gas being input into the VSHPR ( 18 ) does not leak or become contaminated. 
     The gas stream enters the VSHPR ( 18 ) from a gas source by passing through an inlet port ( 224 ). The inlet port ( 224 ) can be of any shape or configuration known in the art but in at least one embodiment it is an industry standard C-10 inlet subassembly. The C-10 inlet subassembly has a specific diameter and comprises a flange (not shown) which impacts against and pushes open the gas source (such as a C-10 adapted gas bottle) once it is attached to the C-10 inlet subassembly. As a result, attaching the gas source to the C-10 inlet assembly places the gas source in fluidic communication with the VSHPR ( 18 ). In at least one embodiment the inlet port ( 224 ) is engaged to a third O-Ring ( 204 ) (see  FIG.35 ) to assure an air tight seal exists between the gas source and the inlet port ( 224 ). 
     The gas flow path ( 245 ) of the VSHPR ( 18 ) utilizes at least two regulator stages ( 228 ) in fluidic communication with each other, one being a first stage ( 228 ′) and a second being a second stage ( 228 ″). Each of the regulator stages ( 228 ) reduces the pressure of the gas stream from a provided level to a reduced level. 
     In at least one embodiment, the first stage ( 228 ′) performs a gross pressure reduction reducing the provided input pressure to an intermediate pressure. In at least one embodiment the input pressure is quantified in terms of thousands of psi (3000-1000 psi) and the intermediate pressure is quantified in terms of hundreds of psi (999.999-100 psi). The second stage ( 228 ″) performs a fine pressure reduction reducing the intermediate pressure to a desired output pressure. In at least one embodiment the intermediate pressure is quantified in terms of hundreds of psi (999.999-100 psi) and the output pressure is quantified in terms of tens of psi (99.99 psi-30 psi). In at least one embodiment, the first stage reduces the pressure from an input pressure of approximately 2000 psi to an intermediate pressure of approximately 200 psi. In at least one embodiment, the second stage reduces the pressure from an intermediate pressure of approximately 200 psi to an output pressure of approximately 40 psi. In at least one embodiment, the VSHPR comprises stages ( 228 ) which lie parallel to each other. By placing the stages ( 228 ) in an oppositely directed parallel configuration, a more compact design than found in prior art gas regulator can be realized. 
     In  FIG. 33 , the inlet port ( 224 ) and the gas output port(s) ( 228 ) are located at or near one side of the VSHPR ( 18 ) and the conduit ( 230 ) which transfers gas between the first stage ( 228 ′) and the second stage ( 228 ″) is located at or near the opposite side of the VSHPR ( 18 ). For purposes of this application, the term “inlet side” refers to the side of the VSHPR where the inlet port ( 224 ) is located and the opposite side of the VSHPR is referred to as the “transfer side”. Similarly any given item can be said to have its transfer side and its inlet side. The transfer conduit ( 230 ) need not necessarily be on the VSHPR&#39;s transfer side and at least one embodiment has the transfer conduit ( 230 ) positioned anywhere in or along the VSHPR ( 18 ). Similarly the gas output(s) ( 228 ) need not necessarily be on the inlet side of the VSHPR ( 18 ) at least one embodiment has it positioned along any external region of the VSHPR ( 18 ). 
     In at least one embodiment, the VSHPR ( 18 ) comprises one or more diagnostic devices ( 231 ). Diagnostic devices ( 231 ) include but are not limited to a pressure gauge ( 219 ) and/or an electrical pressure switch ( 217 ). The pressure gauge ( 219 ) refers to any mechanical and or electrical device known in the art that provides a visible display of the pressure within a particular location of the VSHPR ( 18 ). The pressure switch ( 217 ) monitors the gas pressure and is capable of electronically relaying diagnostic information to any other component of the Gas Chromatograph or any other device. In at least one embodiment the diagnostic device ( 231 ) is in fluidic communication with the junction ( 232 ) connecting gas inlet ( 224 ) and the first stage ( 228 ′). When the pressure at this junction ( 232 ) drops below a particular pre-determined level (which in at least one embodiment is &lt;=300 psi) as a result of the supply in the gas source being either depleted or close to depletion, a new source should be procured and supplied to the VSHPR ( 18 ). In at least one embodiment the pressure switch ( 217 ) is integrated into an online inventory and maintenance system capable of monitoring the gas supply, determining and indicating when new gas sources need to be installed, and appropriately ordering gas sources from vendors or suppliers to assure sufficient inventory is always on hand. In at least one embodiment, at least one diagnostic device ( 231 ) is connected to at least one other component of the VSHPR ( 18 ) by a regulator mount ( 218 ). 
       FIG. 42  illustrates a junction ( 232 ) between the gas inlet ( 224 ) and the first stage ( 228 ′). Extending away from junction ( 232 ) is a diagnostic conduit ( 233 ). The diagnostic conduit ( 233 ) is in fluidic communication with the junction ( 232 ), the inlet port ( 224 ) and the gas source. When the gas source runs low the pressure in the diagnostic conduit ( 233 ) drops below a particular value which is detected by the one or more diagnostic devices ( 231 ) in fluidic communication with the diagnostic conduit ( 233 ). In at least one embodiment, one or more similar diagnostic conduit can connect similar or other diagnostic devices ( 231 ) to other parts of the VSHPR ( 18 ) including but not limited to diagnostic conduits extending into the gas conduit ( 230 ) or any region downstream from the second stage ( 228 ″). 
     Referring now to  FIG. 34  there is shown a more transparent view of the VSHPR ( 18 ). The first stage ( 228 ′) comprises a first piston ( 212 ′) biased to move in one direction. The bias can be achieved by a first biasing mechanism ( 201 ′) such as a spring or other mechanism known in the art. When gas first enters the first stage ( 228 ′) it builds up a countervailing force which is applied according to a vector opposite to the force exerted by the first biasing member ( 201 ′). Eventually the countervailing gas pressure force exceeds that of the biasing force causing the first piston ( 212 ′) to be moved and to sever the fluidic communication between the first junction ( 232 ) and the first stage ( 228 ′). The contained gas is then bled off into the gas conduit ( 230 ) connecting the first stage ( 228 ′) and the second stage ( 228 ″). The bleeding reduces the gas pressure of the gas stream from the input pressure level to the intermediate pressure level. 
     The second stage ( 228 ″) operates in a similar manner to the first stage but has its second piston ( 212 ″) in an orientation opposite to that of the first stage ( 228 ′). As the gas stream flows into the second stage ( 228 ″) from the gas conduit ( 230 ) pressure builds up in the second stage ( 228 ″). When the gas pressure reaches a predetermined level (equal to the output pressure level) the gas exerts a countervailing force which overcomes the biasing force of the second biasing members ( 201 ″). This pushes the second piston ( 212 ″) to sever the fluidic communication between the gas conduit ( 230 ) and the second stage ( 228 ″). The movement also allows the gas to exit the second stage ( 228 ″), enter the second junction ( 238 ) at the reduced output pressure, and flow towards the gas output ( 228 ). Although  FIG. 42  illustrates the two stages ( 228 ) extending along substantially parallel axis, in at least one embodiment they are oriented in any configuration relative to each other. 
     In at least one embodiment, there are multiple stages each having an entering gas pressure and an exiting gas pressure. The exiting gas pressure of an upstream stage provides the entering gas pressure of the immediately downstream stage. The stages have pistons ( 212 ) with narrow shafts and wide compression rings ( 243 ). The compression rings block gas flow by moving into a closed configuration blocking the engagement point between the narrow and wider chambers of the stage when the entering pressure in the narrow chamber exceeds an activation level which is too high. The compression rings move away from the narrow chamber and assumes an open configuration when gas downstream from the compression ring drops to the appropriate level allowing more gas to move downstream at an exiting pressure which is a reduced pressure level. 
     In at least one embodiment the second junction ( 238 ) comprises a closing mechanism ( 210 ) such as a valve. The closing mechanism ( 210 ) allows for the VSHPR ( 18 ) to dynamically alter the flow of the gas stream while using a constant flow gas source such as a commercially available C-10 adapted gas bottle. The closing mechanism ( 210 ) can be a manually rotating device or knob, can be a switch, or can be an electronic device which receives input and provides output to a controller device or computer. In at least one embodiment, the closing mechanism ( 210 ) dynamically interacts with data sent and received between itself and a pressure switch. In at least one embodiment this interaction causes the closing mechanism to shut off gas flow when the pressure from the gas source drops below a particular value or in response to any other user defined reason or data input. The closing mechanism ( 210 ) can be binary (allowing for only an open or closed setting), can shunt gas flow between one, some, or all of the one or more gas outlets ( 208 ), or can be used to modulate the amount of gas that passes through the outlet(s) ( 208 ). 
     Referring now to  FIG. 35  there is illustrated an exploded view of at least one embodiment in which a VSHPR ( 18 ) comprises a number of component parts. In at least one embodiment, at least some of the parts are common commercially available parts which are assembled at least in part according to schematic of  FIG. 3 . In at least one embodiment, a number of O-Rings ( 202 ,  203 ,  204 ,  205 ,  211 ,  214 , and  215 ) are positioned between components to assure airtight seals form between them. The inlet side of the VSHPR is defined by an inlet plate ( 209 ) having three apertures on the inlet side and at least one on the transfer side. One inlet side aperture is the opening to the gas source ( 239 ). In at least one embodiment, the gas source opening has an O-ring ( 204 ) at its end to better assure a fluid tight seal between the VSHPR ( 18 ) and the gas source. Some or all of the inlet port ( 224 ) can be defined by a through hole passing through solid material of the inlet plate, or it can be a hollow polygonal mass placed within an at least partially hollow inlet plate ( 209 ). Similarly the opening to the outlet ( 240 ) can be defined by through holes extending through solid material of the inlet plate ( 209 ) or it can be defined by a hollow polygonal mass placed within an at least partially hollow inlet plate ( 209 ). The outlet opening ( 240 ) has one aperture at the transfer side in fluidic communication with the second stage ( 228 ″) and can have one, two or more branches extending out of apertures at the inlet side of the inlet plate ( 209 ) to of tube adaptors ( 208 ). In at least one embodiment a two branch outlet port adaptor ( 208 ) extends through the inlet plate ( 209 ) and out of the outlet opening ( 240 ) for engagement to other portions of the Gas Chromatograph or to another device. 
     In at least one embodiment, between and engaged to both the inlet plate ( 209 ) and the transfer plate ( 206 ) is a center block ( 225 ). In at least one embodiment, the center block defines the walls of the stages ( 228 ). In at least one embodiment, the center block ( 225 ) is at least partially hollow and contains a shaped polygonal mass of the stage walls. The two or more stages ( 228 ) comprise a wide chamber ( 241 ) and a narrow chamber ( 242 ) in fluid communication with each other. The first stage ( 228 ′) has the narrow chamber ( 242 ′) engaged to either the first junction ( 232 ) or to the source opening ( 224 ). In at least one embodiment between the first stage narrow chamber and the either first junction ( 232 ) or to the source opening ( 224 ) is an O-ring. 
     In at least one embodiment the second stage ( 228 ″) comprises a wide chamber ( 241 ″) adjacent to the outlet opening ( 240 ) and a narrow chamber ( 242 ″) adjacent to the gas conduit ( 230 ). In all of the stages ( 228 ) the piston ( 212 ) comprises at least two portions a wider piston portion ( 243 ) and a narrow piston portion ( 244 ). The wide portion ( 243 ) fits within the wide chamber ( 241 ) and the narrow portion ( 244 ) fits within the narrow chamber ( 242 ). Each of the pistons ( 212 ) are capable of synchronous motions assuring that three different pressure differential equilibriums (the input pressure, the intermediate pressure, and the output pressure) are reached throughout the VSHPR and that the gas stream flows out of the gas flow path ( 245 ) at a constant and even rate. In at least one embodiment the wide portion ( 243 ) comprises two solid masses with an O-ring positioned at least partially between the two solid masses to assure a fluidic seal within the piston ( 212 ). The inventive concept also contemplates all other piston or piston-like equivalents known in the art. 
     In at least one embodiment, the gas conduit ( 230 ) connecting the two stages ( 228 ) is defined by hollow volume within the transfer plate ( 206 ). The hollow volume can itself be defined by a hollow in the solid mass of the transfer plate ( 206 ) or the transfer plate ( 206 ) can itself be somewhat hollow with a solid conduit extending through at least a portion of the somewhat hollow transfer plate ( 206 ). In at least one embodiment the stage end at the transfer side of the two or more stages ( 228 ) are bound by a common O-Ring ( 205 ). This common O-Ring ( 205 ) can further define an open volume in fluidic communication with the gas conduit ( 230 ). 
     In at least one embodiment, between the second stage ( 228 ″) and the gas conduit ( 230 ) is a frit ( 207 ). The frit can also be bound by the common O-ring ( 205 ). The frit can be an assembly comprising fibers or granules which filters out unwanted materials. In at least one embodiment a frit ( 207 ) capable of filtering out materials with a size &gt;=10 microns is positioned adjacent to the second stage ( 228 ″). In at least one embodiment, one or more frits are similarly positioned elsewhere in the VSHPR downstream from the gas source. 
     In at least one embodiment, the center block ( 225 ) is connected to either or both of the transfer plate ( 206 ) and the inlet plate ( 209 ) by screws ( 222 ,  223 ,  226 , and  227 ). In at least one embodiment, some or all of the three are integrated pieces of material. Similarly in at least one embodiment, the diagnostic devices ( 231 ) are connected to the center block ( 225 ) by a mount regulator ( 18 ) which is welded or bolted to the center block ( 225 ) or together define a single integrated piece of material. 
       FIGS. 36 and 37  illustrate perspective views of the center block ( 225 ).  FIG. 36  illustrates the transfer side of the center block where the first stage large chamber ( 241 ′) abuts the transfer plate. Similarly a smaller opening ( 242 ″) engaged to the second stage ( 228 ″) lies on the transfer side of the central block ( 225 ). In at least one embodiment, a frit is positioned between the small chamber ( 242 ″) and the transfer plate. In at least one embodiment, dowel pins ( 216  in  FIGS. 34 and 35 ) can be inserted in dowel holes ( 246 ) in the center block ( 225 ) to hold the common O-Ring ( 205 ) in place. Screw holes ( 247 ) can be used to engage the center block to other portions of the VSHPR ( 18 ). In at least one embodiment, a common O-Ring cavity ( 249 ) is recessed in the center block ( 225 ) to fit the Common O-Ring ( 205 ). 
       FIG. 37  illustrates the inlet side of the center block ( 225 ) where the first stage large chamber ( 241 ′) abuts the inlet plate. Screw holes ( 247 ) connect the center block to the inlet plate and to the mount regulator. A diagnostic conduit ( 233 ) connects the gas flow path to diagnostic components. The narrow chamber ( 242 ′) of the first stage gas and the wide chamber ( 241 ) of the second stage are also shown. O-Rings ( 202  and  203  in  FIG. 35 ) are positioned between these chambers and the inlet plate.  FIGS. 38-40  show lateral perspective views of the center block ( 225 ).  FIG. 37  also shows recesses ( 250  and  251 ) to hold O-Rings in place. 
       FIG. 41  shows a cut away view of at least one embodiment in which the solid mass of the center block ( 225 ) defines the walls of the stages ( 228 ). The center block ( 225 ) also has a diagnostic conduit ( 233 ) and a pre-stage conduit ( 248 ) connecting the second stage ( 228 ″) to the transfer plate. A frit ( 207 ) is positioned at the transfer side of the pre-stage conduit ( 248 ). 
     The portable gas chromatograph disclosed and claimed herein, is compact and lightweight. Furthermore, it may include handles for easy transport from location to location. A perspective view of an embodiment of a gas chromatograph according to the invention is shown in  FIG. 43 . 
       FIG. 44  shows a side panel which allows access to the regulator  18 ′s shut-off valve. 
     Thus, the present invention has the capability of analyzing chemicals, particularly those extracted from the surrounding environment, developing a signature for each component/analyte of the sample, store the signature and send it to a computer via a wireless radio system. 
     Examples of suitable applications include, but are not limited to, portable chemical identification, facility HVAC security, biological agent identifier, and so forth. 
     The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims