Patent Publication Number: US-2011053288-A1

Title: Systems and methods for collection and analysis of analytes

Description:
TECHNICAL FIELD 
     The present invention relates generally to collection and analysis systems, and specifically to systems and methods for collection and analysis of analytes. 
     BACKGROUND 
     The collection and analysis of vapor phase analytes is employed in many environments and applications. One technique for the collection and analysis of analytes is to utilize tubes (metal or glass) that are filled with a packed bed of bulk sorbent material to trap a range of vapor phase analytes. These sorbent tubes may exhibit relatively high pressure drops due to the packed bed height and therefore require a relatively strong pump to pull enough air through the packed bed to capture/trap a vapor phase analyte onto the sorbent material. To desorb the analyte trapped in the sorbent material for subsequent analysis, the tube needs be heated to a sufficient temperature for a sufficient amount of time. Due to the mass of the packed bed, high temperatures and longer desorption times are necessary to efficiently desorb the trapped analyte. For certain types of analytes, the high temperatures can cause degradation of some or all of the analyte resulting in inaccurate and inefficient analysis of the sample. Furthermore, it is often cumbersome and time consuming to obtain replicate analyses of the same sample since it requires switching of individual tubes after each sample and/or analysis. It is also difficult to obtain replicate analyses from a single sorbent tube. Decreasing size, power and sampling/analytical time are of particular interest to most mobile/field sampling applications. 
     SUMMARY 
     In one aspect of the invention, a system for collecting analyte is provided. The system comprises a sampling section disposed on a collection platform and an air source that provides an analyte to be sorbed by the sampling section. In one configuration, the sampling section can be formed of a low pressure drop configuration of sorbent material. 
     In another aspect of the invention, a system is provided for collecting and analyzing analytes. The system comprises one or more sampling sections being formed of a low pressure drop configuration of sorbent material disposed about a collection platform. An air source provides an analyte to be sorbed by a given sampling section of at least one sampling section. A device drives the collection platform to align the given sampling section with the air source. 
     In yet another aspect of the invention, a method is provided for collecting and analyzing analytes. The method comprises providing a collection platform comprising a plurality of sampling sections with each of the plurality of sampling sections being formed of a low pressure drop configuration of sorbent material and repeatedly providing an analyte to be sorbed by a given sampling section of the plurality of sampling sections for each of the plurality of sampling sections. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a system for collection and analysis of analytes in accordance with an aspect of the present invention. 
         FIG. 2  illustrates a rotatable collection disk during collection of analytes in accordance with an aspect of the present invention. 
         FIG. 3  illustrates the rotatable collection disk during analysis of analytes in accordance with an aspect of the present invention. 
         FIG. 4  illustrates an integrated system for collection and analysis of analytes in accordance with another aspect of the present invention. 
         FIG. 5  illustrates another system for collection and analysis of analytes in accordance with another aspect of the present invention. 
         FIG. 6  illustrates yet another system for collection and analysis of analytes in accordance with another aspect of the present invention. 
         FIG. 7  illustrates an example of a methodology for collecting and analyzing analytes in accordance with an aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to systems and methods for the collection and analysis of analytes. In one aspect of the invention, the systems and methods employ a platform containing one or more discrete, low pressure drop configuration of sorbent material. Air containing a given analyte is pumped or vacuumed through the one or more sampling sections during sampling. The low pressure drop configuration eliminates the pressure drop associated with pumping or vacuuming over a length of a tube. After sampling, the previously exposed sampling section is sealed. Once the single or multiple sections have been sampled, they can be removed from the collection system and inserted into an extraction system. Alternatively, the extraction system can be integrated with the collection system. The extraction system can utilize techniques such as solvent and thermal desorption or less destructive, more rapid techniques like ambient pressure desorption ionization or laser desorption to extract/desorb and/or ionize the sorbed analyte from each section. Multiple extractions can be removed from each individual section, for replicate samples analyses resulting in improved confidence. Moreover, the sections may be able to be reconditioned, allowing for subsequent sampling or may be disposable. 
     A sorbent section can be relatively thin (&lt;5 mm) with a negligible pressure drop over a wide range of flow rates (e.g., up to 20 Liters per Minute (LPM)). Conventional sorbent tubes may exhibit low pressure drops at low flows (50 ml/min) but these pressure drops increase significantly with flow rate. Therefore, the current invention includes configurations of sorbent that can sample a larger volume of air in less time without requiring additional pumping power. With efficient transmission of the extractor flow, the desorption of analytes from the sampling section can also be more rapid than conventional sorbent tubes (e.g., &lt;1 min vs &gt;5 min). 
       FIG. 1  illustrates a system  10  for collection and analysis of analytes in accordance with an aspect of the present invention. An air source  12  provides a supply of air containing a given analyte  14  through a low pressure drop configuration of sorptive material layer  16 . Alternatively, the air source  12  can be a vacuum that pulls the analyte  14  through the sorptive material  16 . The sorptive material  16  resides on a collection platform  18  such as a substrate that holds a section of the low pressure drop configuration of sorptive material layer  16 . In one example of the invention, the collection platform  18  is a rotatable disk that includes a plurality of discrete sorbent material sampling sections. In another example of the invention, the collection platform  18  is a continuous roll (reel-to-reel) of sorbent material. The reel can be fed as sample is delivered to the sorbent material. In yet another example, the collection platform can be a roll of fiber, tape or string. In another example of the invention, a single sorbent section can be used. The collection platform can be designed to maximize exposure of the sorbent to the analyte  14 , allow for isolation prior to and after sampling to eliminate sample-to-sample contamination, and minimize pressure drop. 
     An extractor  20  can extract the analyte  14  from the sorbent material  16  and provide the extracted analyte to a detector  22 . The extractor  20  can be designed to rapidly extract/desorb analytes in a manner that minimizes sample degradation and efficiently delivers the analyte in a vapor phase to the detector  22 . The extractor  20  can utilize techniques such as solvent and thermal desorption or less destructive techniques like ambient pressure desorption ionization or laser desorption to extract the sorbed analyte from the sorptive material  16 . The extractor  20  and detector  22  can be a separate extraction system or integrated with a collector system that includes the air source  12 . A power source  24  can provide power to at least one of the air source  12 , the extractor  20  and the detector  22 . 
       FIG. 2  illustrates a rotatable collection disk  30  during collection of analytes in accordance with an aspect of the present invention. The rotatable collection disk  30  includes a plurality of discrete sampling sections  32  disposed about a periphery of the rotatable collection disk  30 . Each discrete sampling section  32  can be formed of a low pressure drop configuration of sorbent material. A given sample section is exposed to air via an air source or vacuum causing an analyte  34  to be sorbed by the sampling section  32 . After sampling, the disk  32  rotates, sealing the exposed sampling section for later analysis and exposing a fresh sampling section for a subsequent air sample. This process can be repeated for each of the plurality of sampling sections  32 . After each of the sampling sections  32  have been exposed to air, the rotatable collection disk  30  can be removed from the collection apparatus and provided to an analysis apparatus, or can enter an analysis stage if the collection and analysis functions are integrated into a single unit. 
       FIG. 3  illustrates the rotatable collection disk  30  during analysis of analytes in accordance with an aspect of the present invention. The disk  30  is loaded into an extractor system and a sorbed analyte on each individual sampling section  32  is extracted/desorbed for analysis using an extractor  36  that employs techniques such as solvent and thermal desorption or an ambient pressure desorption ionization. The extractor  36  can be, for example, an atmospheric pressure ionization source such as a Direct Analysis in Real Time (DART) source or a Desorption ElectroSpray Ionization (DESI) source. An extracted analyte  35  is then provided to a detector for analysis. After sampling, the disk  30  rotates providing another exposed sampling section  32  for extraction by the extractor  36  and detection by the detector for analysis of an extracted analyte. This process can be repeated for each of the plurality of sampling sections  32 . Using this analysis configuration, it may be possible to conduct multiple extractions from each individual sample, thus allowing independent replicates for performing improved statistical analysis. 
       FIG. 4  illustrates an integrated system  50  for collection and analysis of analytes in accordance with another aspect of the present invention. A rotatable collection disk  52  is mounted on a shaft coupled to a rotation device  60 . The rotation device  60  can be, for example, a stepper motor or other motor that can incrementally rotate the rotatable collection disk  52 . The rotatable collection disk  52  includes a plurality of discrete sampling sections  54  disposed about a periphery of the rotatable collections disk  52 . Each discrete sampling section  54  can be formed of a low pressure drop configuration of sorbent material. A given sample section  54  is exposed to air via an air source  58  that can be configured to pump air containing a given analyte or vacuum air to pull the analyte to be sorbed through the sampling section  54 . An extractor  64  can extract the analyte from the sampling sections  54  and provide the extracted analyte to a detector  66 . The extractor  64  can be designed to rapidly extract/desorb analytes in a manner that minimizes sample degradation and efficiently delivers the analyte to the detector  66 . The extractor  64  can utilize techniques such as solvent and thermal desorption or less destructive techniques like ambient pressure desorption ionization or laser desorption to extract the sorbed analyte from each section  56 . 
     A controller  62  is coupled to the air source  58 , the sampling device  60 , the extractor  64  and the detector  66 . The controller  62  can be configured to turn the air source  58  on and off during a collection phase. For example, the controller  62  can be configured to turn on the air source  58  for a given sampling section  54 , turn off the air source  58 , drive the rotatable collection disk or reel or other platform holding the sampling section(s)  52  via the device  60  to align the next given sampling section  54  with the air source  58  and repeat the turning the air source  58  on and off during sampling and rotating the rotatable collection disk or reel or other platform holding the sampling section(s)  52  for each of the plurality of discrete sampling sections  54 . 
     The controller  62  also controls the turning on and off of the extractor  64  for extracting analytes from the sampling sections  54 . The extractor  64  can be an ambient pressure desorption ionization or laser desorption technique that causes the extraction/desorption of the analyte and providing of the analyte to the detector  66 . The detector  66  be responsive to the analyte and provide signals to the controller  62 . The controller  62  can determine the presence and/or type of analyte or the absence of an analyte and/or absence of a given type of analyte based on the signals provided by the detector  66 . The controller  62  can be configured to turn on and off the extractor  64  for a given sampling section  54 , send the signals from the detector  66  to the controller  62 , analyze the signals, rotate the rotatable collection disk or reel or other platform holding the sampling section(s)  52  via the device  60  to align the next given sampling section  54  with the extractor  64  and repeat the turning the extractor  64  on and off during extraction and rotating the rotatable collection disk or reel or other platform holding the sampling section(s)  52  for each of the plurality of discrete sampling sections  54 . Separate controllers for the air source  58 , the sampling device  60 , the extractor  64  and the detector  66  or integrated combinations of controllers may be included. 
     Input/output devices  68  are coupled to the controller  62  and can provide control signals for instructing the system  50  to begin collecting samples. The input/output devices  68  can also include a display for displaying results of the analysis of the collected samples by the controller  62 . The controller  62  can be configured to receiving instruction for analysis of the collected samples. It is to be appreciated that the system  50  can also be configured to take a single sample and analyze a single sample as opposed to collecting a plurality of samples for each of the discrete sampling sections  54  prior to analysis. The controller  62  can also be configured to perform statistical analysis on the plurality of samples to determine the presence and/or type of analyte and provide results of the analysis to the display. 
       FIG. 5  illustrates another system  70  for collection and analysis of analytes in accordance with another aspect of the present invention. The system  70  includes a roll of low pressure drop sampling material  76  disposed on a first reel  72  that winds around a first roller  74  and second roller  78  to unwind onto a second reel  80 . The low pressure drop sampling material  76  can be in the form of a sorbent tape, film, mesh screen or thread. The sampling material  76  passes by an aperture in a wall of the system and is exposed to an air source  84  that contains a given analyte. The analyte is absorbed in a sampling section of the sampling material  76 . The sampling can be performed on a discrete sampling section of the sampling material  76  by stopping the reel or the turning on and off of the air supply or on a continuous sampling section of the sampling material  76  by allowing the reel to continue rolling while the air supply remains on. An extractor  82  is positioned downstream of the air sample to extract the analyte from the low pressure drop configuration sampling material. The extractor  64  can be an ambient pressure desorption ionization or laser desorption technique that causes the extraction/desorption of the analyte and providing of the analyte to a detector (not shown). 
       FIG. 6  illustrates yet another system  90  for collection and analysis of analytes in accordance with another aspect of the present invention. The system  90  includes a thread or fiber of low pressure drop sampling material  98  that includes an sorbed coating of an analyte. The thread or fiber of low pressure drop sampling material  98  is fed through a first end of a first port  92  of the system  90  and exit through a second end of the first port  92 . An extractor (not shown) is positioned at an end of a second port  96  that is transverse to the first port  92  of the system  90 , such that the sorbed coating of the analyte on the a thread or fiber of low pressure drop sampling material  98  can be exposed to the extractor and the analyte can be extracted and provided out a second end of the second port  96  to a detector (not shown). The extractor can be an ambient pressure desorption ionization or laser desorption technique that causes the extraction/desorption of the analyte and providing of the analyte to the detector. 
     In view of the foregoing structural and functional features described above, a methodology in accordance with various aspects of the present invention will be better appreciated with reference to  FIG. 7 . While, for purposes of simplicity of explanation, the methodology of  FIG. 7  are shown and described as executing serially, it is to be understood and appreciated that the present invention is not limited by the illustrated order, as some aspects could, in accordance with the present invention, occur in different orders and/or concurrently with other aspects from that shown and described herein. Moreover, not all illustrated features may be required to implement a methodology in accordance with an aspect of the present invention. 
       FIG. 7  illustrates an example of a methodology  100  for collecting and analyzing analytes in accordance with an aspect of the invention. At  102 , N sampling sections are provided on a collection platform, where N is an integer greater than or equal to one. The collection platform can be but is not limited to a rotatable collection disk or collection tape on a reel or other platforms holding the sampling section(s) with a plurality of discrete sampling sections of sorbent material. At  104 , air is provided to pump or vacuum an analyte to capture the analyte on a given sampling section. At  106 , the pumping or vacuuming is repeated for N number of samples of analyte based on the N number of sampling sections. At  108 , analyte is extracted from each of the N number of sampling sections. At  110 , the extracted analyte is provided to one or more detectors to determine the presence and/or type of analyte for each of the N number of samples or to perform a statistical analysis on the N number of samples to determine the presence and/or type of analyte. 
     What have been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.