Abstract:
A system for analyzing samples using purge and trap concentration is provided. The system includes a plurality of purge and trap concentration units, each adapted to receive a sample and provide a focused analytic sample slug to an analyzer. An analyzer is coupled to each of the plurality of concentrators and receives the focused analytic slugs therefrom. The concentrators are operated in phases from one another.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to automated environmental laboratory analysis. More specifically, the present invention relates to an automated environmental analytic system with improved sample throughput.  
           [0002]    Modern environmental testing laboratories are faced with a continuing increase of samples which must be analyzed. These samples can vary substantially and may be related to, among other things, water analysis, and soil composition.  
           [0003]    [0003]FIG. 1 is a diagrammatic view of an automatic environmental analysis system in accordance with the prior art. System  100  includes multiple vial autosampler  102 , purge and trap concentrator  104 , and gas chromatograph  106 . Autosampler  102  is adapted to receive and maintain a number of vials containing environmental samples. Autosampler  102  is generally equipped with a robotic system to pick a given vial from its respective position and move it to an analyzation site where a sample is removed from the vial. Generally, the sample is tested for volatile organic components. Examples of autosampler  102  can be purchased from Tekmar Company, of Mason, Ohio under the trade designation Solatek 72.  
           [0004]    The sample from autosampler  102  is conveyed to purge and trap concentrator  104 . The functions of purge and trap concentrators are well known. Purge and trap concentrator  104  is conventional and can be obtained from Tekmar Company under the trade designations Model LSC-1, LSC-2, LSC-3, and 3100. Specifically, a generally diffuse analytic stream is received from an autosampler and provided to an adsorbent trap which accumulates the volatile organic components over time. Once a sufficient amount of adsorption has occurred, the sample flow is ceased and the temperature of the adsorbent trap is heated very rapidly to “desorb” the volatile organic components which can then pass as a highly focused analytic slug into an analyzation device, such as a gas chromatograph, for enhanced analysis. There are a number of additional techniques that can be used, such as cyro-focusing, and the like, wherein the analytic slug can be focused further for additional benefits.  
           [0005]    Once the purge and trap operation is complete, the focused slug of analyte is provided to gas chromatograph  106  for analysis. Gas chromatographs are also known and can be obtained from Hewlett Packard Company under the trade designation Model 5890. Generally, gas chromatograph  106  includes a chromatographic column that preferentially adsorbs chemical compounds in an ascending molecular-weight sequence. Based upon the differential adsorption, analysis can provide a relative indication of the different quantities of different molecular-weight substances.  
           [0006]    The current problem that exists with respect to this known configuration illustrated in FIG. 1 is that when maximum sample throughput is required, any dead time leads to inefficiency Specifically, since a purge and trap concentrator includes a pair of phases, adsorb/desorb, the focused analytic slug is only provided to the gas chromatograph during the desorb state. Thus, while the sample is adsorbing upon the trap, no focused samples are provided to the gas chromatograph. This creates dead time and is a limitation upon known automatic environmental laboratory testing.  
           [0007]    If dead time could be reduced, or eliminated, sample throughput could be increased. This would allow more samples to be done in a given period of time thus reducing testing costs while affording the maximum benefit of the operation for the relatively costly pieces of equipment in modern environmental labs.  
         SUMMARY OF THE INVENTION  
         [0008]    A system for analyzing samples using purge and trap concentration is provided. The system includes a plurality of purge and trap concentration units, each adapted to receive a sample and provide a focused analytic sample slug to an analyzer. An analyzer is coupled to each of the plurality of concentrators and receives the focused analytic slugs therefrom. The concentrators are operated in phases from one another. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a diagrammatic view of an automated laboratory testing system in accordance with the prior art.  
         [0010]    [0010]FIG. 2 is a diagrammatic view of an automated laboratory testing system in accordance with an embodiment of the present invention.  
         [0011]    [0011]FIG. 3 is a diagrammatic view of a portion of the system illustrated in FIG. 2, shown in greater detail. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    [0012]FIG. 2 is a diagrammatic view of environmental laboratory analysis system  200  in accordance with an embodiment of the present invention. System  200  bears some similarities to the system illustrated with respect to FIG. 1, and like components are numbered similarly. System  200  includes a pair of purge and trap concentrators,  104 ,  108  that receive samples from respective autosamplers  102 . As illustrated in FIG. 2, purge and trap concentrator  104  is coupled to purge and trap concentrator  108 . Purge and trap concentrator  108  is preferably a conventional purge and trap concentrator, such as the Model 3100 Purge and Trap Concentrator available from Tekmar Company. Concentrator  108  is coupled to analyzation instrument  106  as indicated by line  110 . Instrument  106  is coupled to concentrator  104  and provides carrier gas to concentrator  104  via the carrier gas inlet (not shown in FIG. 2) on concentrator  104 . Concentrator  104  includes sample transfer line  124  that, instead of being coupled to instrument  106 , is provided to a carrier gas inlet (not shown in FIG. 2) on concentrator  108 . Then, sample transfer line  110  from concentrator  108  is coupled to instrument  106 . In this manner, the two concentrators  104  and  108  are essentially plumbed in series.  
         [0013]    In order to facilitate operation with known commercial gas chromatographs, switch box  112  is provided. Known gas chromatographs generate a “GC ready” signal when the gas chromatograph is ready to receive a sample. This signal is generally coupled to a concentrator and used as an indication by the concentrator to provide a sample to the instrument. In order to ensure that concentrators  104  and  108  operate in the correct phase, switch box  112  is used to receive the conventional GC ready signal from analyzation instrument  106  and toggle that signal between concentrators  104  and  108 . Thus, when switch box  112  is installed, it allows the “GC ready” signal to only be sent to one concentrator at a time thus eliminating the potential for duplicate injections. Preferably, the cables used in conjunction with switch box  112  are standard cables facilitating connection to known analyzation instruments and purge and trap concentrators.  
         [0014]    [0014]FIG. 3 is a diagrammatic view of a portion of system  200  shown in greater detail. As illustrated, analyzer  106  is coupled to a source of carrier gas, which is preferably helium (He)  114 . Source  114  is coupled to flow controller  116  which allows a selectable flow of carrier gas to be provided to carrier gas inlet  118  concentrator  104 . Concentrator  104  also includes sample gas inlet  120 , which inlet is coupleable to a supply of purge gas. Concentrator  104  operates in accordance with known techniques to receive a sample, adsorb compounds from the sample on trap  122  and subsequently desorb the components thereby passing a focused analytic slug along heated transferred line  124 . Thus far, the operation of purge and trap concentrator  104  is conventional. However, instead of coupling the sample transfer line  124  directly to instrument  106 , line  124  is provided directly to port  3  on multi-port valve  126  within heated enclosure  128  inside concentrator  108 . This arrangement is preferred over merely coupling sample transfer line  124  to desorb gas inlet  130  because the length of piping from inlet  130  to port  3  on valve  126  would not necessarily be heated on a conventional concentrator. Since line  124  serves the dual purpose of conveying focused analytic slug and carrier gas, it is important to maintain line heating along the entire path through which an analytic slug may pass in order to ensure that condensation does not occur. Concentrator  108  also preferably operates in accordance with known techniques to receive a sample; focus the sample upon trap  134  and provide the focused sample to injection port  136  on instrument  106 . The focused analytic slugs are then conveyed through chromatograph column  138  and analyzed in accordance with known techniques.  
         [0015]    Prior to operation of system  200 , a user will generally set up each autosampler  102  with preferably an equal amount of samples on both systems  102 . The user will then provide the proper method scheduling into each respective concentrator as if each concentrator were running the system as a stand alone unit. Then, the first system, such as concentrator  104 , is started and when that system enters its desorb state, switch  112  will automatically start system #2 (concentrator  108 ). This effectively puts concentrators  104  and  108  180° out of phase. This means that generally, one concentrator is purging while the other is desorbing. This anti-phase operation is facilitated by the provision of six-port multi-position valves  126  and  140  in concentrators  108  and  104 , respectively These multi-position valves generally have two positions wherein a given port will be coupled to the port to its immediate left during one state and coupled to the port to its immediate right during a second state. For example, when concentrator  104  is in its purge mode (also referred to herein as adsorption mode) the ports are coupled as follows:  1 - 2 ;  3 - 4 ; and  5 - 6 . As should be apparent, during this mode carrier gas flows freely through concentrator  104  into concentrator  108 . While concentrator  104  is in its purge mode, concentrator  108  is in desorb mode. In this state, the ports in multi-port valve  126  are coupled as follows:  2 - 3 ;  4 - 5 ; and  6 - 1 . In this manner, carrier gas received by concentrator  108  from concentrator  104  is guided through trap  134  in order to force the focused analytic slug that has accumulated in trap  134  into port  5  of valve  126 , out port  4  of valve  126 , through heated transfer line  142 , and finally into injection port  136 .  
         [0016]    When system  200  switches states, the states of concentrators  104  and  108  are reversed. In this state, the port couplings for valve  140  in concentrator  104  are as follows:  2 - 3 ;  4 - 5 ; and  6 - 1 . Accordingly, concentrator  108  is put into its purge mode during the desorb mode of concentrator  104  and thus the port couplings for valve  126  are as follows:  1 - 2 ;  3 - 4 ; and  5 - 6 . It should be apparent that the focused analytic slug which has accumulated upon trap  122  and concentrator  104  is forced into port  5  of valve  140 , out port  4  of valve  140 , through heated transfer line  124  into port  3  of valve  126 , out port  4  of valve  126 , through sample transfer line  142  into injection port  136 . Thus, while one concentrator purges, the other desorbs and vice versa. In this manner, significant dead time is substantially reduced thereby allowing significantly improved sample throughput.  
         [0017]    Embodiments of the present invention are particularly amenable to combinations of concentrators provided by Tekmar Company. Specific concentrators include, but are not limited to, the Model LSC-1; LSC-2, LSC-3 and 3100 concentrators. Additionally, while embodiments of the present invention have been described with respect to couplings between the multi-port valve and the respective concentrators, that is merely the preferred embodiment. Additional embodiments of the invention could be provided using additional valves and piping external to the concentrators to split or otherwise control the flow of carrier gas through the respective concentrators.  
         [0018]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.