Patent Publication Number: US-2002006356-A1

Title: Water and soil autosampler

Description:
CROSS REFERENCE TO RELATED APPLICATION  
     [0001] This application claims the benefit of U.S. Provisional Patent Application No. 60/188,269, entitled “WATER AND SOIL AUTOSAMPLER,” filed on Mar. 10, 2000 and U.S. Provisional Patent Application No. 60/188,665, entitled “IMPROVED VIAL HANDLING SYSTEM,” filed Mar. 11, 2000, both of which are herein incorporated by reference in their entireties. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] The present invention relates to autosamplers, which are mechanical devices that can be used to extract samples from specimens, prepare the samples for analysis, and provide the samples to an analytical instrument. More particularly, the present invention relates to a sampling station of an autosampler and components thereof, which can be used in performing the above-described tasks.  
       BACKGROUND OF THE INVENTION  
       [0003] Autosamplers are generally used to extract gas and liquid samples from specimens stored in containers such as vials. Once extracted, the sample can be transferred to an analytical instrument for analysis, such as the 3100 Concentrator sold by Tekmar-Dohrmann, Cincinnati, Ohio, U.S.A.  
       [0004] Autosamplers typically use separate sampling stations for extracting liquid and gas samples. One example of such an autosampler is described in U.S. Pat. No. 5,948,360 to Rao et al. and assigned to Tekmar Company, Cincinnati, Ohio, U.S.A. Liquid sampling typically involves extracting a known quantity of liquid from the vial that is presented to the sampling station of the autosampler, adding a standard to the sample, and transferring the sample and the standard to an analytical device. Under certain situations, the specimen must be diluted by a technician by injecting the specimen with a specified volume of methanol or a water-based solution prior to sampling. The extracted sample or methanol extract is then diluted with water prior to analysis by the analytical device.  
       [0005] Gas headspace extraction generally involves injecting the specimen with a solvent, such as water, agitating the specimen, and purging the specimen with a gas. Some autosamplers are adapted to perform static headspace extraction while others are adapted to perform dynamic headspace extraction. In static headspace extraction, the specimen is purged from above the specimen and the headspace is removed and transferred to the analytical device. In dynamic headspace extraction, the specimen is purged from underneath the specimen and the head space is removed and transferred to the analytical instrument. Autosamplers that are capable of performing the above sample extraction procedures include the Precept II and the 7000 HT autosamplers sold by Tekmar-Dohrmann, Cincinnati, Ohio, U.S.A.  
       [0006] The processes of extracting liquid and gas samples using current sampling stations require a technician to perform the standard injections, the methanol dilutions, and other process steps. As a result, in addition to being time consuming, these procedures carry the likelihood of inconsistent injections and a high potential for error. With gas extraction, such as that used for soil analysis, the vial must remain sealed to comply with EPA method 5035. Further time is lost due to the inability to perform both liquid and gas extractions at a single sampling station or autosampler station.  
       [0007] Therefore, a need exists for a sampling station of an autosampler that is capable of performing both liquid and gas extractions while reducing the reliance upon sample preparation by a technician, and remaining compliant with EPA method 5035.  
       SUMMARY  
       [0008] A sampling station for use with an autosampler is provided that is adapted to perform both gas and liquid extractions and automated injections. The sampling station includes a needle, a standard injection system, and an exit port. The needle is adapted to introduce a sample of a specimen to a first flow path. The internal standards system is used to introduce a known quantity of standard into the first flow path to combine with the sample. The sample can be provided to an analytical instrument through the exit port, which is in line with the first flow path. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0009]FIG. 1 shows a perspective view of an example of an autosampler with which embodiments of the present invention can be used.  
     [0010]FIG. 2 is a front plan view of a sampling station.  
     [0011]FIG. 3 is a cross-sectional view of a sampling station.  
     [0012]FIG. 4 is a schematic diagram of a sampling station, in accordance with embodiments of the invention.  
     [0013]FIG. 5 is a simplified schematic of a water control module in accordance with one embodiment of the invention.  
     [0014]FIG. 6 is a cross-sectional view of a metering valve in accordance with an embodiment of the invention.  
     [0015]FIG. 7 is a side plan view of a needle in accordance with one embodiment of the invention.  
     [0016]FIG. 8 is a cross-sectional view of a heated block portion of a needle in accordance with one embodiment of the invention. 
    
    
     DETAILED DESCRIPTION  
     [0017]FIG. 1 shows a perspective view of an autosampler  10  in accordance with one embodiment of the invention. Autosampler  10  can be used to conduct various automated water and soil sampling procedures to extract samples from specimens and deliver the samples to an analytical instrument for analysis. One embodiment of autosampler  10  includes a base unit  12  that includes a vial storage area  14 , and one sampling station  20 .  
     [0018] Vial storage area  14  includes vial storage racks  22  configured to hold vials  24  and receive vials  24  from vial transporter  26 . Alternatively, vial storage racks  22  could be substituted for a vial-carrying rotating carousel (not shown) or other known automated vial advancement device. Vial storage area can also include heating blocks for elevating the temperature of the specimens contained in vials  24  that are stored in racks  22 .  
     [0019]FIGS. 2 and 3 show one embodiment of sampling station  20 . A vial holder assembly  40  can be raised or lowered with the assistance of a suitable elevator system, shown in outline in FIGS. 2 and 3. One embodiment of vial holder assembly  40  includes a vial holder cup  42 . Vial holder cup  42  can include a drain  48  connected to tubing  50  which delivers the contents of vial holder cup  42  to waste. In addition, vial holder cup  42  can include a heating section for heating the contents of a vial  24 . An elevator can raise or lower vial holder cup  42 . Sensors can be used to limit the raising and lowering of vial holder cup  42  between a high or raised position and a lowered position.  
     [0020] Sampling station  20  performs various automated sampling procedures on a specimen contained in a vial  24 , such as water sampling and headspace gas sampling. FIG. 4 shows a schematic diagram of one embodiment of sampling station  20 . Sampling station  20  is generally a fluid circuit that includes a gas/pressure control module  52 , a water control module  54 , a methanol control module  56 , an internal standards system  58 , a needle  60 , and a pump  62 . On-off valves A-F and multi-port valve  64  control the flow of fluid through lines  66 ,  68 ,  70 ,  72 ,  74 , and  76 . Sampling of a specimen contained in a vial  24  can occur when vial holder assembly  40  of sampling station  20  presents the vial  24  by elevating the vial  24  to the raised position causing needle  60  to penetrate the vial  24  and be appropriately positioned for sampling the specimen.  
     [0021] Gas/pressure control module  52  receives a pressurized gas such as helium as shown in FIG. 4. Gas/pressure control module  52  is generally configured to regulate the pressure and flow of gas in sampling station  20  and includes a pressure regulator  78  and a flow controller  80 . Pressure regulator  78  regulates the pressure in line  66 . Flow controller  80  controls the flow of gas into line  66 . Line  66  provides fluid communication between gas/pressure module  52  and internal standards system  58 , valve A, and valve C, using T-connectors  82 . In one embodiment, gas/pressure module  52  can be used to pressurize an external water reservoir  84  to facilitate delivering water to water control module  54 .  
     [0022] Water control module  54  receives water from external water reservoir  84  and delivers water to port  1  of multi-port valve  64  through valve  80 , as shown in FIG. 4. FIG. 5 shows one embodiment of water control module  24  that routes incoming water through a cold water section  86  and a hot water reservoir  88  using a T-connector  82 . The hot water reservoir  88  is configured to heat a volume of water to a desired temperature. A three-port valve  90  is configured to selectively regulate the flow of either hot or cold water through outlet  91 .  
     [0023] Methanol control module  56  is used to provide methanol for use in methanolic dilutions. Methanol control module  56  receives methanol from an external methanol reservoir  92 . Methanol control module  56  is placed in fluid communication with port  5  of multi-port valve  64 . The pressure at port  5  of multi-port valve  64  can be controlled using a pressure regulator  78 .  
     [0024] Pump  62  is generally configured to extract and distribute known quantities of fluid. One embodiment of pump  62  includes a large syringe  94  and a small syringe  96 . Each syringe  94 ,  96  includes an inner plunger  98  that is driven by an external motor  100 . Large syringe  94  is configured to handle large volumes of fluid and small syringe  96  is configured to handle small volumes of fluid. For example, large syringe  94  can have a capacity from 1-25 ml (milliliters) and small syringe  96  can have a capacity from 2.5-250 μl (microliters). With this arrangement, large syringe  94  can accurately extract or distribute fluid volumes on the order of 1 ml and small syringe  96  can extract or distribute fluid volumes on the order of 2.5 μl.  
     [0025] Internal standards system  58  allows for the automated injection of at least one standard into line  70 . The standard can be, for example, an internal standard, a calibration standard, a surrogate standard or a matrix spike. The internal standard is typically methanolic or water-based. FIG. 4 shows one embodiment of internal standards system  58  that includes one or more internal standard lines  102 . Each internal standard line  102  is placed in fluid communication with line  66  using an appropriate connector, such as a cross-connector  104  that is capable of connecting three internal standard lines  102  to line  66 . Additional internal standard lines  102  could be added using a suitable connector. Each internal standard line  102  includes a pressurized internal standard vessel  106  containing a volume of standard, a metering valve  108 , and a restrictive tubing section  110 . Internal standard vessels  106  can contain the same or different standards. A second cross connector  104  connects the restrictive tubing section  110  to waste.  
     [0026] Metering valves  108  are generally used to introduce a known volume of standard into line  70  or a first flow path  114 , from one of the internal standard lines  102  or a second flow path  116 . One embodiment of metering valve  108 , shown in FIG. 6, includes a first inlet and outlet  118  in line with first flow path  114  and a second inlet and outlet  120  in line with second flow path  116 . A moveable guide member  122  is positioned between the first and second inlet and outlets  118 ,  120  and includes an internal cavity  124  of a known volume. Valve  108  is defined as being in a “first position” when guide member  122  is positioned to allow fluid communication between first inlet and outlet  118  through internal cavity  124 , as shown in FIGS. 4 and 6. Valve  108  is defined as being in a “second position” when guide member  122  is positioned to allow fluid communication between second inlet and outlet  120  through internal cavity  124  shown in dashed lines in FIG. 6. The volume of internal cavity  124  can be sized to be compatible with various calibration standards. In one embodiment, internal cavity  124  has a volume of 5-10 μl.  
     [0027] Restrictive tubing section  110  is configured to inhibit the flow of standard through cavity  124  of metering valve  108  when metering valve  108  is in the second position by reducing the pressure drop across metering valve  108 . Without restrictive tubing section  110  the standard contained within pressurized internal standard vessel  106  would surge through metering valve  108  when in the second position. Restrictive tubing section  110  preferably limits the flow rate of the standard to approximately 30 ml/minute at 10 psi. One embodiment of restrictive tubing section  110  includes conventional tubing having a sufficiently small inner diameter and length to produce the desired pressure drop across restrictive tubing section  110 . For example, it has been found that conventional tubing having an inner diameter of 0.010 inch and a length of 8 feet produces a sufficient pressure drop across restrictive tubing section  110  such that the flow of standard through metering valve  108  is reduced to an acceptable rate.  
     [0028] Another embodiment of internal standards system  58  includes check valves  126 . Check valves  126  are placed in line with internal standard lines  102  to prevent the back flow of standard, or headspace gas in vessel  106 , into other internal standard lines  102  and line  66 . A check valve  126  can also be placed in line with line  66  near valve C, as shown in FIG. 4, to prevent the back flow of fluid into line  66  from line  76 . One embodiment of the check valves  126  has a 0.5-1 psi crack pressure.  
     [0029] The process of introducing a standard into line  70  includes rotating guide member  122  of metering valve  108  to the second position thereby opening fluid communication between the second inlet and outlet  120  and causing pressurized internal standard vessel  106  to expel standard into internal cavity  124 . As the standard flows into internal cavity  124 , internal cavity  124  is overfilled with standard with the excess standard being expelled out second outlet  120  of metering valve  108  and into restrictive tubing section  110 . Additional materials in line  102  are forced out cross-connector  104  and sent to waste. Once internal cavity  124  is filled with standard, guide member  122  is moved to the first position cutting off fluid communication between the second inlet and outlet  120  and opening fluid communication between the first inlet and outlet  118  of metering valve  108  to introduce the standard contained in internal cavity  124  to line  70  or first flow path  114 . In this manner, multiple standard injections can be made to the contents of line  70  simultaneously using multiple internal standard lines  102 . In addition, multiple injections of the same standard can be made to line  70  by sweeping the fluid contained in flow path  70  such that each internal cavity  124  of metering valves  108  is clear of standard prior to another injection of standard into line  70 . As a result, the volume of standard injected into flow path  70  can be controlled in amounts that are multiples of the volume of internal cavity  124  of metering valves  108 . Automation of internal standard system  58  can be achieved through control circuitry (not shown) that is configured to actuate valves  108  between the first and second positions as desired.  
     [0030] Needle  60  is generally configured to perform fluid and gas headspace extractions and fluid and gas injections on a specimen contained in a vial  24  that is presented to sampling station  20  as mentioned above. FIG. 7 shows one embodiment of needle  60  that includes a bottom stage  128 , a middle stage  130 , a top stage  132 , and a heated block  134 . Each of the needle stages  128 ,  130  and  132 , are hollow tubing sections that include apertures  136  which allow each of the needle stages  128 ,  130  and  132 , to perform a fluid extraction or injection. In one embodiment, bottom stage  128  includes several small apertures  136  and middle and top stages  130 ,  132  each include a single large aperture  136 , as shown in FIG. 7. In one embodiment, bottom stage  128 , middle stage  130 , and top stage  132 , are concentrically aligned.  
     [0031] Bottom stage  128  generally serves the purpose of extracting fluid from vial  24  for water sampling and purging vial  24  for dynamic headspace gas extraction. Bottom stage  128  includes a pointed tip  138  for piercing a septum of a vial  24  (depicted as a dashed line) that is presented to sampling station  20 . Bottom stage  128  is placed in fluid communication with port  2  of multi-port valve  64  through line  74 . Middle stage  130  generally serves the purpose of performing fluid injections into vial  24 , such as standard injections, and for purging vial  24  during a static headspace extraction. Middle stage  130  is placed in fluid communication with on-off valve F through line  70 . Top stage  132  generally serves the purpose of an outlet for gas headspace extractions. Top stage  132  is placed in fluid communication with on-off valves C and D through line  76 , as shown in FIG. 4.  
     [0032] Heated block  134  generally serves the purpose of preventing gasses flowing in middle stage  130  and top stage  132  from condensing. One embodiment of heated block  134  is shown in FIG. 8. Bottom stage  128  extends through lower heated portion  140  and upper heated portion  142  of heated block  134 . Middle stage  130  extends through lower heated portion  140  and into upper heated portion  142 . Middle stage channel  144  connects to middle stage channel  130  and opens fluid communication between line  70  and middle stage  130  of needle  60 . Top stage  132  extends into lower heated portion  140  of heated block  134 . Top stage channel  146  provides fluid communication between line  76  and top stage  132  of needle  60 . Lower and upper heated portion  140 ,  142  of heated block  134  can be heated to approximately 100° C. using resistive heating elements or by other methods used in the industry. Lower and upper passages  148 ,  150 , through which the various needle stages pass, can be sealed using a ferrule combination or a collet as is common in the industry.  
     [0033] Embodiments of sampling station  20  can perform water sample extractions with multiple standard injections, methanol injections, methanolic dilutions, static headspace extractions, and dynamic headspace extractions. All of these procedures can be automated using appropriate control circuitry. Tables I-V list the sequence of operations for conducting the above-mentioned procedures in accordance with various embodiments of the invention. In the operation tables, the individual on-off valves designated by capital letters (A-F) are considered to have two positions: “0” designating off, and “1” designating on, in the table columns. Multi-port valve  64  has common port 0. Only the open port (1-5) will be listed in the operation tables. A “-” will be used to indicate that a particular valve position of less importance. The sample extractions performed by sampling station  20  will generally be discussed with reference to a single internal standard line  102 , even though several could be used simultaneously as discussed above. As a result, only a single metering valve  108  will be shown in the tables with a “1” indicating that metering valve  108  is in the first position and a “2” indicating that metering valve  108  is in the second position. Additionally, the “vial position” column of the operation tables will indicate whether the vial  24  is up (U) or down (D). When the vial  24  is up (U), the vial  24  is in the raised position where needle  60  is in position to sample the specimen. When the vial  24  is in the down (D) position, needle  60  is not in position to sample the specimen and vial  24  can either be removed from the sampling station or a new vial  24  can be placed in position for sampling.  
     [0034] The examples of sample extraction operations described in Tables I-V each utilize similar procedures for purging and rinsing the stages of needle  60 , the various fluid lines, and the syringes of pump  62 . These stages can be automated by a control system (not shown). Each of the described rinsing and purging procedures can be repeated as desired. The large syringe  94  can be rinsed by first extracting water from water control module  54  through port  1  of multi-port valve  64  and valve B. Next, the extracted water can be discharged out of large syringe  94  into line  68  through valve B. Finally, the water can be swept through port  4  of multi-port valve  64  to waste by introducing gas through valve A and valve B. Similarly, small syringe  96  can be rinsed with water by extracting water from water control module  54  through port  1  of multi-port valve  64  and sweeping the water through port  4  of multi-port valve  64  to waste with gas.  
     [0035] The stages  128 ,  130 , and  132  of needle  60  can be purged as needed. Typically, bottom stage  128  and middle stage  130  are rinsed and purged with water and helium. Water is extracted from water module  54  through port  1  of multi-port valve  64  and valve B using large syringe  94  of pump  62 . Bottom stage  128  can be rinsed and purged by expelling water from large syringe  94  into line  68  through valve B and sweeping the water through port  2  of multi-port valve  64 , line  74 , and bottom stage  128  by introducing helium gas through valves A and B. The discharged water can be collected by vial holder cup  42  and drained to waste. Middle stage  130  can be rinsed and purged by first extracting water from water module  54  using large syringe  94  as described above. Next, water is discharged from large syringe  94  through valve B into line  68 . With metering valve  108  in the first positiori, valve E off, and valve F on, helium is introduced from gas/pressure control module  52  through valves A, B, and port  3  of multi-port valve  64  to flush the contents of line  68 , line  70 , and line  72  through middle stage  130  of needle  60  and into vial holder cup  42  where the water is drained to waste. Both bottom and middle stages  128 ,  130  can be purged with only helium if desired. Top stage  132  is generally purged with gas by discharging helium gas from gas/pressure control module  52  through line  66 , valve C, line  76 , and out top stage  132  of needle  60 . Additionally, line  68  connecting valve B to common port  0  of multi-port valve  64  can be rinsed by injecting water from large syringe  94  into line  68  and purging line  68  of its contents by introducing gas through valves A and B and sweeping the contents out port  4  of multi-port valve  64  to waste.  
     [0036] Each of the sampling procedures generally starts at a purge ready state where sampling station  20  waits for a purge ready signal from the concentrator or other analytical instrument indicating that it is ready to receive a sample. In this state the vial is down and valves A, B, C, D, E, and F are closed. The open valve of multi-port valve  64  is unimportant as is the position of metering valve  108 .  
     [0037] Table I provides one possible sequence of operations that could be conducted to extract a water sample from a specimen and transfer the specimen along with one or more standards to a concentrator or analytical instrument for analysis. After the standby, rinsing, and purging stages, a vial containing a specimen is presented to needle  60  such that apertures  136  of bottom stage  128  are immersed into the specimen. Large syringe  94  of pump  62  extracts a known volume of the specimen through apertures  136  of bottom stage  128 , port  2  of multi-port valve  64 , and valve B. Large syringe  94  can be primed by discharging some of the extracted sample through valve B and port  4  of multi-port valve  64  to waste. Standards are introduced to line  70  by selectively actuating the desired metering valves  108  into the second position causing corresponding internal cavities  124  to fill with the desired standard. Metering valves  108  are actuated to their first position and large syringe  94  expels a known quantity of the sample into line  68  through valve B. The sample and standard are flushed with helium gas through valves A, B, port  3  of multi-port valve  64 , through metering valves  108  and valve E to the water concentrator or analytical instrument. Alternatively,  
               TABLE I                          Water Sample Extraction                                                                                 METERING   MULTI-PORT   VIAL       MODE OF OPERATION   A   B   C   D   E   F   VALVE 108   VALVE 64   POSITION               LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE LARGE SYRINGE   1   1   0   0   0   0   —   4   D       (RINSE)       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE BOTTOM STAGE   1   1   0   0   0   0   —   2   D       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE LINES 70 AND   1   1   0   0   0   1   1   3   D       195       STANDBY AND   0   0   0   0   0   0   —   —   D       WAIT FOR PURGE READY       RAISE VIAL   0   0   1   0   0   0   —   —   U       EXTRACT SAMPLE   0   1   1   0   0   0   —   2   U       PRIME SYRINGE   1   1   1   0   0   0   —   4   U       FILL STANDARD(S)   0   0   0   0   0   0   2   3   U       SWEEP SAMPLE AND   1   1   0   0   1   0   1   3   U       STANDARD(S) TO WATER       CONCENTRATOR       RETURN VIAL TO TRAY   0   0   0   0   0   0   —   —   D                  
 
     [0038] either large syringe  94  or small syringe  96  can be used to flush the sample and standard through metering valves  108  and valve E to the water concentrator or analytical instrument. If necessary, additional standard injections can be made by repeating the steps of moving the metering valves  108  to the second position to fill the internal cavities  124  with standard, rotating the metering valves  108  to the first position, and sweeping the standards in line  70  to the water concentrator with helium or by expelling a small known amount of sample from large syringe  94  thereby creating a positive pressure flow in the direction of the analytical instrument, which in turn “clear” the metering valve. If no further samples are to be extracted, the vial can be returned to the holding tray. Finally, the lines, needle  60 , and pump  62  can be purged and rinsed as described above.  
     [0039] Table II describes a sequence of operations that can be conducted by one embodiment of sampling station  20  to inject a specimen with methanol. Prior to injecting the specimen with methanol, bottom stage  128  of needle  60 , large syringe  94 , small syringe  96 , line  70 , line  74 , and line  68  can be purged or rinsed to remove any possible contaminants using the various methods described above. Next, a vial  24  containing a specimen is presented to sampling station  20  by sampling station  18 . Large syringe  94  extracts a known quantity of the methanol from methanol control module  56  through port  5  of multi-port valve  64 . Large syringe  94  can be primed by discharging and sweeping a small amount of the extracted methanol through port  4  of multi-port valve  64  to waste, and line  68  can be rinsed if desired. A known quantity of the methanol is introduced to line  68  and transferred to the vial by sweeping gas through valve A, valve B, port  3  of multi-port valve  64 , metering valves  108  (in the first position), valve F, and middle stage  130  of needle  60 . With the methanol injection complete, the specimen and methanol can be  
               TABLE II                          Methanol Injection                                                                                 METERING   MULTI-PORT   VIAL       MODE OF OPERATION   A   B   C   D   E   F   VALVE 108   VALVE 64   POSITION               LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE LARGE SYRINGE   1   1   0   0   0   0   —   4   D       (RINSE)       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE BOTTOM STAGE   1   1   0   0   0   0   —   2   D       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE MIDDLE STAGE AND   1   1   0   0   0   1   1   3   D       METERING VALVES       STANDBY AND   0   0   0   0   0   0   —   —   D       WAIT FOR PURGE READY       RAISE VIAL   0   0   0   0   0   0   —   —   U       EXTRACT METHANOL USING   0   0   0   0   0   0   —   5   U       LARGE SYRINGE       INJECT METHANOL INTO   1   1   0   0   0   1   1   3   U       VIAL       EXTRACT SAMPLE WITH   0   0   0   0   0   0   —   2   U       SMALL SYRINGE       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       TRANSFER WATER AND   0   0   0   0   1   0   1   3   U       SAMPLE TO CONCENTRATOR       RETURN VIAL TO TRAY   0   0   0   0   0   0   —   —   D                  
 
     [0040] mixed in the vial  24  as desired. Additional methanol injections can be performed by returning the vial  24  to vial storage area  14 , retrieving a new vial  24 , and repeating the above-described procedure.  
     [0041] One embodiment of sampling station  20  can perform methanolic dilutions on the order of 2.5 parts methanol to 1000 parts water on specimens that have been previously injected with a suitable volume  
               TABLE III                          Methanolic Sample Extraction &amp; Dilution                                                                                 METERING   MULTI-PORT   VIAL       MODE OF OPERATION   A   B   C   D   E   F   VALVE 108   VALVE 64   POSITION               LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE LARGE SYRINGE   1   1   0   0   0   0   —   4   D       (RINSE)       SMALL SYRINGE WATER   0   0   0   0   0   0   —   1   D       EXTRACTION       PURGE SMALL SYRINGE   1   1   0   0   0   0   —   4   D       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE BOTTOM STAGE   1   1   0   0   0   0   —   2   D       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE MIDDLE STAGE   1   1   0   0   0   1   1   3   D       AND METERING VALVES       STANDBY AND   0   0   0   0   0   0   —   —   D       WAIT FOR PURGE READY       RAISE VIAL   0   0   0   0   0   0   —   —   U       EXTRACT SAMPLE WITH   0   0   0   0   0   0   —   2   U       SMALL SYRINGE       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       TRANSFER WATER AND   0   0   0   0   1   0   1   3   U       SAMPLE TO       CONCENTRATOR       RETURN VIAL TO TRAY   0   0   0   0   0   0   —   —   D                  
 
     [0042] of methanol, such as by the above embodiment of sampling station  20 . This embodiment of the invention will be described with reference to Table III. After purging and rinsing the various components and lines of sampling station  20  as desired, a known volume of the specimen and methanol is extracted using small syringe  96  through bottom stage  128  of needle  60  and port  2  of multi-port valve  64 . Next, large syringe  94  extracts a known volume of water, typically around 5 ml, from water control module  54 . Known values of the extracted water (typically 5 ml) and the sample (as little as 5 μl) are then introduced to line  68  and swept through port  2  of multi-port valve  64 , valves  108  (in first position), and valve E to the water concentrator for analysis. Finally, the vial can be returned to the vial holder. Additional methanolic dilutions can be conducted by sampling station  20  by retrieving another vial  24  and repeating the above-described procedure.  
     [0043] Sampling station  20  is also capable of performing both static and dynamic headspace gas extractions. Table IV describes the sequence of operations for performing static headspace extractions and Table V describes a sequence of operations for performing dynamic headspace extractions. Several of the steps are duplicated and will only be described once.  
     [0044] As with the other procedures described above, the components of sampling station  20  are generally purged and rinsed prior to performing the headspace gas extraction. A vial  24  containing a specimen, typically a soil sample, is presented to needle  60  of sampling station  20  after receiving the appropriate signal from the concentrator that it is ready for a sample. In one embodiment, the presented vial can be heated up to 90° C. in the vial holder cup  42 . Large syringe  94  extracts a volume of water from water control module  54 . Internal standards system  58  introduces a known quantity of at least one standard to line  70  by the method described above. Large syringe  94  expels a known quantity of water into line  68  through valve B. Helium gas is introduce through valve A, valve B, and port  3  of multi-port valve  64  to sweep the water and standard through valve F and out middle stage  130  of needle  60  to mix with the specimen. Generally, bottom stage  128  is immersed into the specimen and water mixture and middle stage  130  is above the specimen and water mixture. Next, the contents of the vial are agitated using a stir mechanism or other suitable device.  
     [0045] For static headspace extraction (Table IV) the contents of the vial are purged by injecting helium gas through middle stage  130  of needle  60  to flush the headspace gas out top stage  132  of needle  60 . This is accomplished by routing the helium from gas/pressure control module  52  through valves A, B, port  3  of multi-port valve  64 , valve F, and out aperture  136  of middle stage  130 . The headspace gas is exhausted through aperture  136  of top stage  132  by opening valve D. The expelled headspace gas is then sent to a gas chromatograph or other suitable analytical instrument for analysis. Finally, the vial  24  can be returned to the vial holder and the procedure can be repeated if desired.  
               TABLE IV                          Static Headspace Gas Extraction                                                                                 METERING   MULTI-PORT   VIAL       MODE OF OPERATION   A   B   C   D   E   F   VALVE 108   VALVE 64   POSITION               LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE LARGE SYRINGE   1   1   0   0   0   0   —   4   D       (RINSE)       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE BOTTOM STAGE   1   1   0   0   0   0   —   2   D       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE MIDDLE STAGE AND   1   1   0   0   0   1   1   3   D       METERING VALVES       STANDBY AND   0   0   0   0   0   0   —       D       WAIT FOR PURGE READY       RAISE VIAL   0   0   0   0   0   0   —   —   U       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       FILL STANDARD(S)   0   0   0   0   0   0   2   —   U       SWEEP WATER AND   1   1   0   0   0   1   1   3   U       STANDARD       INJECT GAS INTO MIDDLE   1   1   0   1   0   1   1   3   U       STAGE AND PURGE VIAL       OUT TOP STAGE       RETURN VIAL TO TRAY   0   0   0   0   0   0   —   —   D                  
 
     [0046] For dynamic headspace extraction (Table V) the vial is purged by injecting helium gas through apertures  136  of bottom stage  128  of needle  60  by opening valves A, B, and port  2  of multi-port valve  64 . Headspace gas in the vial  24  is then allowed to escape through aperture  136  of top stage  132  of needle  60  and through valve D where it is sent to a gas chromatograph or other suitable analytical instrument for analysis. Finally, the vial  24  can be returned to the vial holder and the procedure can be repeated if desired.  
               TABLE V                          Dynamic Headspace Gas Extraction                                                                                 METERING   MULTI-PORT   VIAL       MODE OF OPERATION   A   B   C   D   E   F   VALVE 108   VALVE 64   POSITION               LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE LARGE SYRINGE   1   1   0   0   0   0   —   4   D       (RINSE)       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE BOTTOM STAGE   1   1   0   0   0   0   —   2   D       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       PURGE MIDDLE STAGE AND   1   1   0   0   0   1   1   3   D       METERING VALVES       STANDBY AND   0   0   0   0   0   0   —   —   D       WAIT FOR PURGE READY       RAISE VIAL   0   0   0   0   0   0   —   —   U       LARGE SYRINGE WATER   0   1   0   0   0   0   —   1   D       EXTRACTION       FILL STANDARD(S)   0   0   0   0   0   0   2   —   U       SWEEP WATER AND STANDARD   1   1   0   0   0   1   1   3   U       INJECT GAS INTO BOTTOM   1   1   0   1   0   0   —   2   U       STAGE AND PURGE VIAL OUT       TOP STAGE       RETURN VIAL TO TRAY   0   0   0   0   0   0   —   —   D                  
 
     [0047] During the above-described headspace gas extractions, heated block  134  can be heated to prevent the condensation of the headspace gas. Typically, heated block  134  is maintained at an elevated temperature of approximately 40-90° C. Similarly, valve D can also be heated to approximately 40-200° C. to prevent headspace gas from condensing during transport to the analytical instrument.  
     [0048] Although the invention has been described with reference to specific embodiments of a water and soil autosampler, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention. Thus, the fluid circuit could be modified from that described above without departing from the basic function of the present invention of providing a means of performing both liquid and gas headspace (both static and dynamic) extractions and automated injections in a single sampling station. For example, the function of the several of the on-off valves could be performed by a single multi-way or multi-port valve to reduce the number of valves in the system. Consequently, a single multi-way valve could replace valves C and D (FIG. 4) to control the flow of gas through flow path  76  between a source of pressurized gas and the exit port through which the prepared sample is delivered to the analytical instrument.